Music Perception with Hearing Aids. Phd Thesis. Martin Kirchberger

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Doctoral Thesis

Music perception with hearing aids

Author(s): Kirchberger, Martin J.

Publication Date: 2015

Permanent Link: https://doi.org/10.3929/ethz-a-010608245

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DISS. ETH NO. 23167

MUSIC PERCEPTION WITH HEARING AIDS

A dissertation submitted to attain the degree of

DOCTOR OF SCIENCES of ETH ZURICH

(Dr. sc. ETH Zurich)

presented by

MARTIN JULIAN KIRCHBERGER

Dipl. Ing. Graz University of Technology

born on 12.02.1984

citizen of Germany

accepted on the recommendation of

Prof. Dr. Marcy Zenobi-Wong Prof. Dr. Frank Russo Prof. Dr. Ewen MacDonald

2015

ii Acknowledgements

Acknowledgements

A thesis is like a song: Its development requires good ideas, experimenting, listening, and fine- tuning. Good ideas, however, can only resonate with the right instruments and ensemble. I am grateful for the support that I received and want to use this opportunity to thank Marcy, Frank, Markus, Schelle, and Stef for being the keys to the realization of this project.

Thank you Stef for funding my thesis. I applied during a hiring freeze and so I tried hard to hit the right pitch. Your genuine interest in music research laid the foundation for this work and has always remained an inspiration for me.

Thank you Schelle for helping me out when I could not attend my presentation due to a scheduling conflict with the Hear the World video shoot. I also appreciate that you always found time for my questions, although your responsibilities had steadily been growing. Experiencing your broad knowledge and incredibly sharp judgment helped me increase the tempo in my thesis.

Thank you Markus for your support in work-related and non-work-related matters. You never hesi- tated to discuss technical issues outside office hours and kept me grounded in turbulent times. Your ability to find structure in complex issues and your creativity in solving them is simply amazing. You are one of the main reasons why I enjoyed working at Sonova so much, and let me assure you that your entire team shares this opinion in unison.

Thank you Frank for your incredible commitment and your passion for this topic. Your point of view added new dimensions to this work. I admire how you managed to explain complex issues in plain English, and I learned to put myself in the position of a reader while writing from you. Our weekly discussions helped to keep the rhythm, and our project visits, both in Switzerland and Canada, further added to the progression.

Thank you Marcy for orchestrating the whole project. This thesis would not have happened if it weren’t for you. Thanks for integrating me into your team and for your hospitality on numerous occasions. Your thoughtful supervision struck a chord.

iii

Für meine Eltern und meine Maus

« Music expresses that which cannot be put into words and that which cannot remain silent. »

Victor Hugo

vii

viii Abstract

Abstract

Hearing loss affects the quality of life in various situations such as in conversations or when listening to music. The research on hearing loss and hearing aids has focused primarily on improving speech intelligibility. To date, there is a lack of understanding of how to process music in hearing aids to optimize music perception in hearing-impaired listeners.

As a first step, a novel research tool was developed to make music perception measureable. The Adaptive Music Perception (AMP) test allows for quantifying music perception by establishing physical discrimination thresholds. Test participants make perceptual judgments about the musical dimensions of meter, harmony, melody, and timbre while the underlying low-level dimensions (e.g., brightness or attack of timbre) are adaptively manipulated until discrimination thresholds can be determined.

To investigate the effect of hearing loss on music perception, 19 normal-hearing and 21 hearing- impaired listeners submitted to the AMP test. Significant differences were found in 7 of the 10 low- level dimensions, implying that hearing loss affects the perception of meter, harmony, melody, and timbre.

In a follow-up study, the effect of hearing aids on music perception was investigated by comparing the performance of 25 hearing-impaired listeners on the AMP test with and without hearing aids. The discrimination thresholds for the low-level dimensions ‘level’ from the meter test and ‘attack’ from the timbre test were marginally worse with hearing aids. The impairment of timbre perception was found to correlate significantly with the strength of dynamic compression in hearing aids.

Based on these results, potential for optimization was identified in the dynamic compression of hearing aids. The optimization was guided by an investigation of the dynamic range in recorded music. To account for the diversity in music, the analysis was conducted in a genre-specific manner on 1000 songs from the genres chamber music, choir, opera, orchestra, piano, jazz, pop, rap, rock, and schlager. The dynamic range analysis revealed that the modern genres pop, rap, rock, and schlager had smaller dynamic ranges than jazz and the classical genres chamber music, choir, opera,

ix Abstract orchestra, and piano. As opposed to conventional opinions, the dynamic range of all music genres was generally smaller than the dynamic range of speech.

The dynamic compression in hearing aids was optimized by reducing the compression strength relative to the dynamic compression standard NAL_NL2. A linear and a semi-compressive setting were chosen as test conditions to optimize the processing and perception of modern and classical music, respectively. Thirty-one hearing-impaired participants evaluated the sound quality of music segments of three classical (choir, orchestra, and opera) and two modern genres (pop and schlager) under the NAL-NL2 reference condition and the linear and semi-compressive test conditions. The results showed that the perceived sound quality was highest in the linear condition and lowest in the NAL-NL2 reference condition for all genres tested.

The second potential for improving music perception with hearing aids was identified in frequency lowering. Frequency lowering is a signal-processing strategy that maps high frequencies, which are inaudible to the impaired ear, to lower, audible frequencies. State-of-the-art implementations have been developed to increase speech intelligibility, and their transfer functions violate the harmonic structure of music. A novel approach - harmonic frequency lowering - allows to lower musical content while preserving the harmonic ratios and pitch chromas in music. Nineteen participants evaluated music detail and the sound quality of music excerpts processed with harmonic frequency lowering and the benchmark conditions nonlinear frequency compression, low-pass filtering, and no processing. Harmonic frequency lowering yielded significant improvements in the perception of music detail without detrimental effects on sound quality.

In brief, this thesis investigated how hearing loss and hearing aids affect music perception to inform the optimization of hearing-aid technology for music. Two strategies regarding dynamic compression and frequency lowering were developed and proved successful in improving music perception in hearing-impaired listeners.

x Zusammenfassung

Zusammenfassung

Die Schädigung des Hörvermögens wirkt sich in vielen Bereichen des Lebens beeinträchtigend aus. Die Gesprächsteilnahme ist erschwert und der Genuss beim Musikhören leidet. Im Fokus der Hör- forschung liegt seit Jahrzehnten die Verbesserung der Sprachverständlichkeit. Musik spielte bislang eine untergeordnete Rolle und es besteht ein enormer Nachholbedarf, Hörgeräte für die Signalver- arbeitung von Musik zu optimieren.

Um Musikwahrnehmung messbar zu machen wurde in einem ersten Schritt der AMP Test (Adaptive Music Perception Test) entwickelt. Dieser ermöglicht es, Unterschiede in musikrelevanten Wahr- nehmungsdimensionen zu quantifizieren. Während die Versuchsteilnehmer Höraufgaben zu Met- rum, Harmonie, Melodie und Timbre bearbeiten, werden die darunterliegenden physikalischen Dimensionen (z.B. Lautstärke, Frequenz, oder Länge bei Metrum) in Abhängigkeit von der Richtig- keit der Antworten adaptiv verändert bis ein Wahrnehmungsschwellenwert ermittelt werden kann.

Die Auswirkungen einer Hörschädigung auf die Musikwahrnehmung wurde mit Hilfe des AMP Tests an 19 normalhörenden und 21 hörgeschädigten Probanden untersucht. In der hörgeschädigten Gruppe wurden in 7 der 10 physikalischen Dimensionen signifikant höhere Schwellenwerte gemessen, welche eine Beeinträchtigung der Wahrnehmung von Metrum, Harmonie, Melodie und Timbre durch Hörverlust belegen.

In einer zweiten Studie wurde die Wirkung von Hörgeräten auf die Musikwahrnehmung untersucht. Fünfundzwanzig hörgeschädigte Probanden führten den AMP Test einmal mit und einmal ohne Hörgeräte aus. In den Dimensionen Lautstärke und Helligkeit, welche die Wahrnehmung von Met- rum und Timbre betreffen, wurden höhere Wahrnehmungsschwellenwerte in der Versuchsdurch- führung mit Hörgeräten gemessen. Die Stärke der Dynamikkompression in Hörgeräten konnte hierbei als signifikanter Faktor für die Beeinträchtigung der Wahrnehmung von Timbre identifiziert werden.

Aufgrund dieser Ergebnisse wurde ein Optimierungspotential der Musiksignalverarbeitung in der Dynamikkompression verfolgt. Hierzu wurde eine Analyse zur Dynamik von Musik anhand von 1000

xi Zusammenfassung kommerziell erhältlichen Songs durchgeführt. Um die Vielfalt an Musik kontrolliert zu erfassen, wurden jeweils 100 Songs aus den verschiedenen Genres Chor, Kammermusik, Orchester, Oper, Piano, Jazz, Pop, Rap, Rock, und Schlager gewählt. Die Dynamikanalyse erwies, dass die modernen Genres Pop, Rap, Rock, und Schlager weniger dynamisch sind als Jazz und die klassischen Genres Chor, Kammermusik, Orchester, Oper und Piano. Entgegen der allgemeinen Auffassung konnte zu- dem gezeigt werden, dass alle getesteten Genres eine geringere Dynamik aufweisen als Sprache.

Aus dieser Erkenntnis wurde abgeleitet, dass die Stärke der Dynamikkompression in Hörgeräten für Musik geringer eingestellt werden sollte als es der wissenschaftliche Standard NAL-NL2 für Sprache vorschlägt. Als Optimierungsoption für moderne Genres wurde eine lineare Einstellung vorgeschla- gen und als Optimierung für klassische Genres wurde eine halbkompressive Option empfohlen. Beide Einstellungen wurden der NAL-NL2 Referenz in einem Hörversuch mit 31 hörgeschädigten Probanden und Musikbeispielen aus drei klassischen (Chor, Oper und Orchester) und zwei modernen (Pop und Schlager) Genres gegenübergestellt. Die wahrgenommene Klangqualität war in der linearen Einstellung bei allen Genres signifikant am höchsten und auch die halbkompressive Einstel- lung wurde als signifikant besser empfunden als die NAL-NL2 Referenz.

Das zweite Optimierungspotential der Musiksignalverarbeitung mit Hörgeräten wurde im Bereich der spektralen Kompression (Frequency Lowering) verfolgt. Frequency Lowering ermöglicht es, ho- he Frequenzen, welche für das geschädigte Ohr unhörbar sind, auf tiefere, hörbare Frequenzen abzubilden. Die bestehenden Implementierungen wurden ursprünglich für Sprachsignale entwickelt und verletzen hierbei jedoch Strukturen, welche für die Musikwahrnehmung wichtig sind. Ein neuer Ansatz – Harmonic Frequency Lowering - erlaubt es, die harmonischen Strukturen und die Tonklasse im Signal aufrechtzuerhalten. In einem Hörversuch verglichen 19 Probanden den Detailreichtum und die Klangqualität von Musikbeispielen, welche entweder unprozessiert waren oder mit Harmo- nic Frequency Lowering, einer nichtlinearen Frequenzkompression oder einem Tiefpassfilter verar- beitet wurden. Die Versuchsteilnehmer konnten mit Harmonic Frequency Lowering am meisten Detail in der Musik wahrnehmen ohne an Klangqualität einzubüssen.

Zusammengefasst wurden in dieser Arbeit die Auswirkungen von Hörschäden mit und ohne Hörge- räteversorgung auf die Musikwahrnehmung untersucht, um daraus Leitlinien für die Hörgeräteop- timierung zu gewinnen. Zwei Optimierungsansätze wurden im Bereich der Dynamikkompression und der spektralen Kompression entwickelt und deren positive Wirkung konnte anhand von Studien mit hörgeschädigten Probanden erfolgreich nachgewiesen werden.

xii Contents

Contents

Acknowledgements ...... iii Abstract ...... ix Zusammenfassung ...... xi List of Figures ...... xvii List of Tables ...... xx List of Equations ...... xxii List of Abbreviations ...... xxiii Chapter 1 Introduction ...... 25 1.1 Music Perception ...... 25 1.2 Hearing and Hearing Loss ...... 28 1.3 Hearing Aids ...... 29 1.3.1 Dynamic compression ...... 29 1.3.2 Frequency lowering ...... 31 1.3.3 Research question and rationale ...... 32 1.4 Study Overview ...... 33 References ...... 34 Chapter 2 Development of the Adaptive Music Perception Test ...... 41 Abstract ...... 42 2.1 Introduction ...... 43 2.1.1 Motivation ...... 43 2.1.2 Concept ...... 44 2.1.3 Objective ...... 44 2.1.4 Hypothesis ...... 45 2.2 Materials and Methods...... 46

xiii Contents

2.2.1 General test design ...... 46 2.2.2 Adaptation ...... 46 2.2.3 Sound stimuli ...... 47 2.2.4 Test procedure ...... 47 2.2.5 Meter subtest: level, pitch, and duration ...... 48 2.2.6 Harmony subtest: dissonance and intonation ...... 49 2.2.7 Melody subtest: melody-to-chord ratio ...... 50 2.2.8 Timbre subtest: brightness, attack, and spectral irregularity ...... 51 2.2.9 Music experience ...... 52 2.2.10 Participants ...... 52 2.3 Results ...... 53 2.3.1 Meter subtest ...... 55 2.3.2 Harmony subtest ...... 57 2.3.3 Melody subtest ...... 58 2.3.4 Timbre subtest ...... 59 2.4 Discussion ...... 59 2.4.1 D1: Level, meter subtest ...... 60 2.4.2 D2: Pitch, meter subtest ...... 60 2.4.3 D3: Duration, meter subtest ...... 61 2.4.4 D4: Dissonance, harmony subtest ...... 61 2.4.5 D5: Intonation, harmony subtest ...... 62 2.4.6 D6 & D7: melody-to-mhord ratio I & II (MCR I & II), melody subtest ...... 62 2.4.7 D8: Brightness, timbre subtest ...... 62 2.4.8 D9: Attack, timbre subtest...... 62 2.4.9 D10: Spectral irregularity, timbre subtest ...... 63 Acknowledgments ...... 65 References ...... 66 Chapter 3 Music Perception in Aided and Unaided Hearing-Impaired Listeners ...... 71 Abstract ...... 71 3.1 Introduction ...... 71 3.2 Materials and Methods...... 72 3.2.1 Participants ...... 72

xiv Contents

3.2.2 AMP test ...... 73 3.2.3 Procedure ...... 74 3.3 Results ...... 75 3.4 Discussion ...... 76 3.5 Conclusion ...... 76 Acknowledgments ...... 77 References ...... 78 Chapter 4 Dynamic Range across Music Genres and the Perception of Dynamic Compression in Hearing-Impaired Listeners ...... 81 Abstract ...... 82 4.1 Introduction ...... 82 4.1.1 Compression in music production ...... 82 4.1.2 Compression in hearing aids ...... 83 4.1.3 Dynamic range of music ...... 85 4.2 Experiment I: Dynamic Range of Music across Genres ...... 85 4.2.1 Stimuli ...... 85 4.2.2 Analysis ...... 87 4.2.3 Results ...... 88 4.2.4 Conclusion ...... 91 4.3 Experiment II: Effect of Compression Ratio on Music Perception ...... 91 4.3.1 Rationale ...... 91 4.3.2 Participants ...... 92 4.3.3 Test conditions ...... 94 4.3.4 Test stimuli ...... 96 4.3.5 Listening test ...... 99 4.3.6 Results ...... 100 4.3.7 Discussion ...... 102 4.4 General Discussion ...... 104 Acknowledgments ...... 106 References ...... 107 Appendix ...... 112 Chapter 5 Harmonic Frequency Lowering: Effects on the Perception of Music Detail and Sound Quality ...... 135

xv Contents

Abstract ...... 136 5.1 Introduction ...... 136 5.1.1 Benefit of frequency lowering on speech intelligibility ...... 138 5.1.2 Effect of frequency lowering on sound quality of speech and music ...... 138 5.2 Description of harmonic frequency-lowering algorithm ...... 141 5.3 Materials and Method ...... 142 5.3.1 Participants ...... 142 5.3.2 Stimuli ...... 144 5.3.3 Procedures ...... 145 5.4 Results ...... 148 5.4.1 Pretest ...... 148 5.5 Main Test ...... 149 5.6 Discussion ...... 151 5.7 Conclusion ...... 152 Acknowledgments ...... 152 References ...... 154 Chapter 6 General Conclusion ...... 161 Reference ...... 166 Chapter 7 Outlook ...... 167 7.1 Adaptive Music Perception Test ...... 167 7.2 Dynamic-Range Analysis and Dynamic Compression ...... 167 7.3 Harmonic Frequency Lowering ...... 168 References ...... 170

xvi List of Figures

List of Figures

Figure 1:1 Simplified schematic of the processing stages of the auditory system. 28 Figure 1:2 Example of a signal being separated into multiple components by a filter bank...... 29 Figure 1:3 Schematic Input-output function (solid line, left abscissa) and gain curves (dashed line, right abscissa) of a frequency band in a hearing aid. Input levels above the compression threshold (CT) are compressed; input levels below the compression threshold are expanded...... 30 Figure 1:4 Examples of input-output function for frequency transposition and frequency compression...... 32 Figure 2:1 The mid-level and low-level dimensions of the Adaptive Music Perception test. D1–D10 indicates dimension 1–10; MCR, melody-to-chord ratio; Sp. Irreg., spectral irregularity...... 45 Figure 2:2 Spectrogram of the AMP test audio stimuli. The reference tone (0 sec - 0.4 sec) in the calibration, meter subtest, and timbre subtest is followed by the reference cadence of the harmony subtest (0.8 sec - 3.8 sec) and by one example of the melody subtest (4.2 sec – 10.2 sec)...... 47 Figure 2:3 The subdominant (IV), dominant (V) and tonic (I) dyad of the harmony subtest...... 49 Figure 2:4 A schematic plot of the harmonic spectrum of the root note and the fifth in just intonation or equal temperament. Deviations are exaggerated for better visibility...... 50 Figure 2:5 Two examples of the melody subtest. The upper bars depict two melodies from melody set 1 that have the same contour (up-down-up). The lower bars depict two melodies from melody set 2 that have a different contour (down-up-down; up-down-up)...... 51 Figure 2:6 Box-plot (median, quartiles, whiskers: 1.5 x IQR, & individual data points) showing the level D1 (dB), the pitch D2 (Hz), and the duration D3 (sec) thresholds of the meter subtest by group and session. (1 NH_t: normal-hearing / test sesssion, 2 NH_r: normal-hearing / retest session, 3 HI_t: hearing-impaired / test session, 4 HI_r: hearing-impaired / retest session)...... 56 Figure 2:7 Box-plot (median, quartiles, whiskers: 1.5 x IQR, & individual data points) showing the dissonance D4 (Hz) and the intonation D5 (Hz) thresholds of the harmony subtest by group and session. (1 NH_t: normal-hearing / test sesssion, 2 NH_r: normal-hearing / retest session, 3 HI_t: hearing-impaired / test session, 4 HI_r: hearing-impaired / retest session)...... 57

xvii List of Figures

Figure 2:8 Box-plot (median, quartiles, whiskers: 1.5xIQR, & individual data points) showing the melody-to-chord ratio I D6 (dB) and the melody-to-chord ratio II D7 (dB) thresholds of the melody subtest by group and session. (1 NH_t: normal-hearing / test sesssion, 2 NH_r: normal-hearing / retest session, 3 HI_t: hearing-impaired / test session, 4 HI_r: hearing-impaired / retest session)...... 58 Figure 2:9 Box-plot (median, quartiles, whiskers: 1.5xIQR, & individual data points) showing the brightness D8 (dB), attack D9 (sec), and spectral irreguliarity D10 (dB) thresholds of the timbre subtest by group and session. (1 NH_t: normal- hearing / test sesssion, 2 NH_r: normal-hearing / retest session, 3 HI_t: hearing- impaired / test session, 4 HI_r: hearing-impaired / retest session)...... 59 Figure 4:1 Dynamic ranges of speech and 10 different music genres. The lines represent percentiles in dB (SPL) across frequency in kHz (99 th : upper dashed line, 90 th : upper solid line, 65 th : thick line, 30 th : lower solid line, and 10 th : lower dashed line)...... 89 Figure 4:2 Dynamic range comparison between different music genres and across frequency. The dynamic range are calculated as the difference between the 99 th and 30 th percentiles according to the IEC 60118-15 standard...... 90 Figure 4:3: Schematic gain curves within a compression band for the linear, semi- compressive, and compressive condition. The compression ratio of the semi- compressive condition ( = ∆/∆) is half the compression ratio of the compressive condition ( = 2 ∗ ∆/∆)...... 95 Figure 4:4 Example loudness curves of the linear, semi-compressive, and compressive version. (Here for participant 29 and stimulus 3)...... 96 Figure 4:5 Dynamic range of the test sample in Experiment II (left column) and the audio corpus in Experiment I (right column) for the genres choir, opera, orchestra, pop, and schlager. The lines represent percentiles in dB (SPL) across frequency in kHz (99 th : upper dashed line, 90 th : upper solid line, 65 th : thick line, 30 th : lower solid line, and 10 th : lower dashed line)...... 97 Figure 4:6 Example screen of the main test...... 99 Figure 4:7 Ratings and standard errors for the data on dynamics, quality, and loudness in the linear, semi-compressive, and compressive condition...... 102 Figure 5:1 Examples of the input-output mapping functions for the different frequency lowering schemes frequency transposition (FT), linear frequency compression (LFC), and nonlinear frequency compression (NFC). (FT: cut-off frequency 5 kHz, peak frequency: 6 kHz, frequency shift 3 kHz; LFC: compression ratio 3:2; NFC: cut-off frequency 2 kHz, compression ratio CR nfc : 1.7...... 137 Figure 5:2 Spectrum of a tone dyad of two complex tones with fundamental frequencies at 800 Hz (black) and 2000 Hz (blue). The cut-off frequency for the nonlinear frequency compression (NFC) condition was set to 2 kHz and the frequency shift for the frequency transposition (FT) condition was determined at 3 kHz, half the peak frequency at 6 kHz. The cut-off frequency for harmonic

xviii List of Figures frequency lowering (HFL) was set at 4 kHz. New components to the original version after frequency lowering are marked in green...... 140 Figure 5:3 Schematic of the different input-output functions that were evaluated in the main test...... 145 Figure 5:4 Long-term average spectra of the four music segments in the original version (OV) / LP condition, the HFLo condition and the spectra of the lowered signal for a gain weight of 0 dB...... 146 Figure 5:5 Example screen of the main test...... 147 Figure 5:6 Mean ratings and standard errors for detail and quality in the 5 conditions under test (Orig: Original, NFC: nonlinear frequency compression, HFLi: harmonic frequency lowering with individual cut-off frequency, HFLo: harmonic frequency lowering with default cut-off frequency fc = 4 kHz, LP: low pass)...... 150 Figure 7:1 Example input-output function (solid line) for harmonic frequency lowering with double octave transposition...... 168

xix List of Tables

List of Tables

Table 2:1 The music questionnaire (column 1 and 2) and the respective points allocation (column 3) to determine an objective music experience (ME) measure for each participant...... 53 Table 2:2 Characteristics of the test participants: sex, audiometric data, degree of hearing loss (HL) as defined by ASHA, music experience (ME), and age...... 54 Table 2:3 Results of the repeated measure ANCOVA analysis for each dimension of the tests. The condition hearing loss was the dependent variable, music experience (ME) the covariate...... 55 Table 2:4 Forced-entry multiple linear regression for each dimension. Predictors were hearing loss (HL), age, and music experience (ME)...... 56 Table 3:1 Characteristics of the test participants: sex, audiometric data, hearing loss (HL), music experience (ME), age, and hearing aid (CR: compression ratio). . 73 Table 3:2 Mean discrimination thresholds in the unaided and aided condition and the ANOVA statistics for the dimensions of the meter, harmony, and timbre subtests of the AMP test...... 75 Table 4:1 Peer-reviewed research exploring the effect of different compression settings on music perception in hearing-impaired listeners (CR: compression ratio, AT: attack time, RT: release time, CT: compression thresholds, WDRC: wide dynamic range compression (multiband dynamic compression), ADRO: adaptive dynamic range compression, HA = hearing aid...... 86 Table 4:2 Additional criteria for each genre that the songs and stimuli (45-s segments) had to meet beyond the iTunes genre classification...... 87 Table 4:3 Characteristics of the test participants: audiometric data (dB HL), age (yrs), hearing-aid experience / HAE (yrs), music experience / ME (range from -3: low to 4: high), and coupling (dome and receiver). Note: NT indicates a hearing threshold that was not tested...... 92 Table 4:4: Details about the 20 music segments from experiment II...... 98 Table 4:5 Audio corpus used for the dynamic range analysis sorted by genre and composer/interpret...... 112 Table 5:1: Characteristics of the test participants and the individual parameters for the nonlinear frequency compression algorithm: audiometric data (dB HL), age (yrs), hearing aid experience / HAE (yrs), and music experience / ME (scale

min: -3, scale max: 4), cut-off frequency / Fc, and compression ratio / CR nfc for the NFC (nonlinear frequency compression) condition. NT indicates a hearing threshold that was not tested...... 143

xx List of Tables

Table 5:2 Gain weights in dB at the point of detection and preference for HFLi and HFLo...... 149 Table 5:3 Statistics of pair-wise ANOVAs for music detail between all 5 conditions. The Bonferroni-corrected significance level is p=0.005...... 150

xxi List of Equations

List of Equations

Equation 3:1 – Calculation of the compression ratio CR...... 75 Equation 5:1 – Input-output function for linear frequeny compression...... 136 Equation 5:2 – Input-output function for nonlinear frequeny compression;

constant hereinafter referred to as CR nfc (compression ratio for nonlinear frequency compression)...... 136

xxii List of Abbreviations

List of Abbreviations

AMP test Adaptive Music Perception test ANCOVA analysis of covariance ANOVA analysis of variance CAMEQ Cambridge method for loudness equalization CR compression ratio for dynamic compression

CR nfc compression ratio for nonlinear frequency compression (NFC) D dimension dB decibel DLM dynamic loudness model DRC dynamic range compression DSL desired sensation level FC frequency compression FT frequency transposition HFL harmonic frequency lowering HI hearing-impaired HL hearing loss LFC linear frequency compression LP low pass MCR melody-to-chord ratio ME music experience NAL-NL2 National Acoustic Laboratories, non-linear prescription formula 2 NFC nonlinear frequency compression NH normal-hearing SL sensation level SPL sound pressure level

xxiii

Chapter 1: Introduction

Chapter 1 Introduction

Music is an evolutionarily old and universal aspect of life. Not only do we enjoy music as individuals but also in groups as music allows us to experience the same emotion together. According to Bersch-Burauel (2004), the average time that adults listen to music in everyday situations accumu- lates to almost 3 hours per day. Besides music listening, one in five individuals rehearses an instrument or performs on a regular basis (Swiss Federal Statistical Office, 2008). In addition, music is used in therapy to improve the psychological and physiological health of individuals (Koelsch 2009). Music-supported therapy has yielded improvements in the recovery of motor functions in stroke and Parkinson’s patients (Altenmüller et al. 2009; Thaut et al. 1996) and in the treatment of autism (Whipple 2004), dementia (Koger, Chapin, & Brotons 1999), and Alzheimer’s disease (Smeijsters & Puhr 1997). Music has been used to support second-language learning and memory more generally (Good, Russo, & Sullivan 2014; Wallace 1994). Furthermore, it has been shown that music training can lead to improved nonmusical skills, such as cognitive (Hassler, Birbaumer, & Feil 1985; Gardiner

1996; Hetland 2000; Schellenberg 2004), language, and literacy skills (Barwick et al. 1989; Standley & Hughes 1997; Chan, Ho, & Cheung 1998; Anvari et al. 2002; Ho, Cheung, & Chan 2003; Overy 2003).

1.1 Music Perception Perception is the process of identifying and interpreting sensory impressions (Schacter, Gilbert, & Wegner 2011). Our ability to perceive is not fixed but evolves continuously with making experiences (Emmenegger & Schwind 2008). The experiences contribute to a knowledge and understanding of structures which serve as a reference: we hear pitches in terms of their places in the tonal framework and we hear tones occurring in relation to a metrical framework of beats (Dowling 2010).

Grouping allows us to interpret our auditory environment more efficiently (Deutsch 1999). We group auditory events based on simple Gestalt-like principles such as proximity. Elements that are close together in time and space are more likely to be grouped than are those found further apart. When tones are presented in rapid sequence for example and these are drawn from two different pitch ranges, the listener perceives two melodic lines in parallel: one derived from the lower tones

25 Chapter 1: Introduction and the other from the higher ones (Bregman 1994). Another grouping principle is similarity. When one instrument plays a melody and a different instrument plays chords simultaneously, we still detect the melody based on the similarity of the timbre, even when the tones produced by the different instruments overlap considerably in pitch (Koelsch & Schröger 2008). Further principles of auditory grouping are auditory continuity and spatial location (Darwin 1997; Deutsch 1999).

In contrast to sinusoidal tones, naturally sustained tones such as those produced by musical instruments are made up of components whose frequencies are integer or near-integer multiples of the fundamental. The auditory system exploits this feature to combine a set of harmonically related components into a single sound image which gives rise to strongly fused pitch impressions (Deutsch 1999). Pitch can be divided into a two-dimensional percept of pitch chroma and pitch height (Drobisch 1852; Stumpf 1890; Révesz 1914; Bachem 1937; Bachem 1950; Shepard 1982). Chroma defines the position of a tone within the octave whereas pitch height defines the octave. This con- ceptualization is reflected in Western music notation: “G5” for example denotes the chroma “G” in octave 5. Within an octave, Western music distinguishes between 12 chromas which are separated by a semitone. The frequency ratio of the semitone interval depends on the tuning system. In historical tuning system such as the Pythagorean tuning or just temperament, the frequency ratios of of adjacent tones vary depending on their position within the scale (Hunt 1992). In equal temperament, the interval ratio between adjacent tones is labeled a semitone and equal to the twelfth root of 2 ( √2 = 1.058).

Apart from atonal music that lacks a tonal center, music does normally not use all 12 chromas but a restricted number of chromas to form a modal scale. Typical scales in Western music are major or minor scales using seven chromas such as in A-major: A, B, C#, D, E, F#, G#. The first tone of the scale, the tonic, is the tonal center of the scale and lays the foundation for a tonal hierarchy that is established within the scale (Krumhansl 1990). The tonic, dominant (V) and median (III) position of the major scale for example are most stable while the leading tone (VII) is the most unstable position. Musicians and also non-musicians have an implicit knowledge of tonality (Bigand, Parncutt, & Lehrdahl 1996; Janata et al. 2003; Toiviainen & Krumhansl 2003). Listeners therefore raise expecta- tions of what pitches are coming next and respond emotionally if the expectancies are violated (Sloboda 1998; Bharucha 2002; Grewe et al. 2007; Altenmüller & Bernatzky 2015).

The perception of consonance and dissonance is closely related to the perception of tonality, especially in the case of aesthetic dissonance (Plomp 1976; Dowling 2010). Aesthetic dissonance of an

26 Chapter 1: Introduction auditory event is determined by the musical context in which the auditory event is embedded. A single tone can be aesthetically dissonant if it is unstable and creates tension. Contrary to aesthetic dissonance, tonal or acoustic dissonance is not dependent on the context but only on the harmonic structure of the tone cluster. The acoustic dissonance of complex tones is the sum of the disso- nances produced by the interaction of their harmonics (Kameoka & Kuriyagawa 1969a,b). Combina- tions of complex tones are less dissonant when the ratios of the fundamental frequencies are sim- pler. Complex tones separated by a fifth (3:2) or a major third (5:4) for example are thus more consonant than complex tones separated by a minor second (16:15). The absolute evaluation of dissonance has evolved with time over the last centuries (Ebeling 2009). Intervals previously considered dissonant gradually substituted consonant chords (Carter 1945).

Although the perception of a stimulus cannot be fully deduced from its physical properties alone but would require to somehow consider the historic or individual experiences, there are universal correlations between the physics and the perception of sound. To a high degree, the perception of loudness correlates with the amplitude of an oscillation and pitch correlates with the frequency of an oscillation (Fricke & Louven 2008). The mapping of physical dimensions to psychic dimensions, however, is more difficult when it comes to timbre. Timbre is the perceptual attribute by which we distinguish instruments even if they play the same note with the same loudness (ANSI 1973; Don- nadieu 2007). Timbre is multidimensional and brightness and attack are two dimensions that have consistently been identified as important (Grey 1977; Wessel 1979; Krumhansl 1989; McAdams & Cunibile 1992; Krimphoff, McAdams, & Winsberg 1994; McAdams et al. 1995). A physical correlate of brightness is the spectral centroid of a sound and a physical correlate of attack is onset rapidity, the time a sound needs to develop its full amplitude (Krimphoff, McAdams, & Winsberg 1994). In- harmonic tones have weaker pitch salience (Terhardt, Stoll, & Seewann 1982) and provide a less stable perception of the tonal hierarchy (Russo et al. 2007).

Rhythm refers to the temporal organization of events as the music unfolds in time (Thaut 2005). The psychic correlate of time is duration. We perceive beats as pulses marking off units which are equal in duration (Dowling & Harwood 1986). We perceptually group beats into patterns of two, three, or four (Fraisse 1982). Meter imposes an accent structure on these beats by regularly alter- nating between strong and weak beats (Clarke 1999). Accents can be induced by changes of the beats such as in intensity or pitch.

27 Chapter 1: Introduction

In brief, the physical and cognitive-perceptual nature of music comprises simultaneous and sequen- tial components (Thaut 2005). This makes music perception unique among the perception of other art forms such as visual art or language.

1.2 Hearing and Hearing Loss Sound passes various processing stages of the auditory system until it evokes a perception in the brain (Figure 1:1).

Outer ear Middle ear · Pinna · Eardrum Cochlea Auditory nerve Central system · Ear canal · Ossicles

Figure 1:1 Simplified schematic of the processing stages of the auditory system.

The pinna collects impinging sound waves and channels them via the ear canal to the eardrum. The eardrum vibrates and the vibrations are transmitted through a three-ossicular chain to the cochlea. The geometry of the eardrum and the ossicles yield an amplification of the pressure of the vibrations by a factor of 22 (Geisler 1998). This amplification allows for an efficient transformation of the original air-borne sound waves into liquid-borne sound waves in the cochlear fluids. The waves in the cochlea cause deflections of the stereocilia of the hair cells which trigger electrical impulses that are then relayed via the auditory nerve and nuclei in the brain stem to the primary and secondary auditory cortices (Seifritz et al. 2001). Two types of hair cells can be distinguished: the inner hair cells and the outer hair cells (Purves et al. 2001). The inner hair cells function as sensory receptors while the outer hair cells actively influence the mechanics of the cochlea (Yates 1995). This so-called active mechanism (Oxenham & Wojtczak 2010) tunes the cochlea to achieve higher frequency selectivity and works as a dynamic compressor so that soft sounds are audible and loud sounds are still comfortable.

Hearing loss is the impairment of the transmission of sound at any processing stage of the auditory system. An impairment of the outer or middle ear results in conductive hearing loss (Johnson & Lalwani 2000). Sound is hindered or not efficiently transformed on its way to the inner ear which leads to an attenuation of sound levels and higher auditory thresholds. Common causes are ceru- men in the ear canal, damage to the eardrum, or stiffening of the ossicles (Northern 1984; Zadeh & Selesnick 2001).

28 Chapter 1: Introduction

An impairment of the cochlea involves damages to the structures inside the cochlea such as the inner and outer hair cells (Liberman 1989). Damage to the inner hair cells leads to reduced sensitivity and thus higher auditory thresholds for hearing-impaired individuals (Liberman, Dodds, & Lear- son 1986). Damage to the outer hair cells affects frequency selectivity and the range of levels between threshold and discomfort becomes smaller. This abnormal growth of loudness with increasing sound level is also known as loudness recruitment (Fowler 1937; Davis & Silverman 1970). Common causes of cochlear hearing loss are exposure to intense sound, use of ototoxic chemicals, or infection. Hearing loss as a side-effect of ageing, presbyacusis, is also of cochlear nature.

Retrocochlear hearing loss refers to impairments at stages beyond the cochlea. Damage to the auditory nerve for example can be caused by the growth of a tumor (Weaver & Northern 1976).

1.3 Hearing Aids Hearing aids are medical products for the treatment of hearing loss. They are computers that process the incoming signal according to the needs of the user. State-of-the-art hearing aids incorporate various signal-processing units that handle and transform a signal on its way from the microphone to the speaker. Two of these signal-processing units, the dynamic compressor and the frequency lowering unit, are especially important for music perception.

1.3.1 Dynamic compression Hearing aids apply gain to the input signal so that soft signals become audible and loud signals stay below the user’s discomfort level. The level-dependent gain results in a dynamic compression of the signal. Because hearing loss will vary across frequencies, the gain needs to be frequency-dependent. To achieve this, frequency aids commonly partition the signal into multiple frequency bands (Figure 1:2). State-of-the-art hearing aids contain filter banks with up to 20 bands. A gain is applied to each

filter bank 2

-2 original input signal 0 20 40 60 80 100 120 140 160 180 200 10 5

5 0

-5 0 0 20 40 60 80 100 120 140 160 180 200 5

amplitude -5 amplitude 0 -10 0 20 40 60 80 100 120 140 160 180 200 -5 0 20 40 60 80 100 120 140 160 180 200 time (msec) 5

-5 0 20 40 60 80 100 120 140 160 180 200 time (msec) Figure 1:2 Example of a signal being separated into multiple components by a filter bank. 29 Chapter 1: Introduction band individually.

Figure 1:3 shows a schematic gain curve and the corresponding input-output function of a frequency band. For input levels above the compression threshold (CT), the gain decreases with increasing signal level. The strength of the compression is specified as the compression ratio (CR). A compression ratio of 3:1 for example increases the output level by 1 for an increase in input level of 3 Below the compression threshold, the gain is reduced to avoid that internal noise becomes audible. In state-of-the-art hearing aids, the gain curve can further include a linear or less compressive segment in the transition from expansion to compression. There are established prescription standards for speech that define the compression parameters as a function of hearing loss (Scollie et al. 2006; Moore, Glasberg, & Stone 2010; Dillon et al. 2011). There are no compression standards for music.

100 Δy 90 Δx 80

50 50

output level level (dB) output 40 40

30 30

20 20 (dB) gain

10 10

CT 10 20 30 40 50 60 70 80 90 100 level (dB SPL)

Figure 1:3 Schematic Input-output function (solid line, left abscissa) and gain curves (dashed line, right abscissa) of a frequency band in a hearing aid. Input levels above the compression threshold (CT) are compressed; input levels below the compression threshold are expanded.

The input-output function and gain curves as displayed in Figure 1:3 are target values for static signals and/or when the system is in a steady state. Music and speech, however, are dynamic signals which can have abrupt changes in level. The effective compression of a signal depends on how fast the system reacts to changes in input level. Hearing aids usually react very fast to increases in level

30 Chapter 1: Introduction so that sudden peaks do not result in excessively high output levels (attack). In comparison, the time to increase the gain due to decreases in signal level is longer (release). There is, however, no standard that defines attack or release precisely and hearing-aid manufacturers use their proprie- tary methods. One potential method is to define attack or release as the time required for a gain to reach a certain percentage (e.g., 90%) of the target value.

1.3.2 Frequency lowering The usability of conventional amplification for the treatment of hearing loss has various limits, especially when the patient suffers from profound high-frequency hearing loss. The power of the speaker can be insufficient to provide the hearing-aid wearer with the output level needed for the audibility of the high-frequency components. Speakers further produce distortions at high output levels. Moreover, high gains can lead to feedback problems in the hearing aid. Furthermore, dead regions are more likely to occur in the higher frequencies (Peepers et al. 2014). Dead regions are regions of non-functioning inner hair cells and/or neurons on the basilar membrane which distort or inhibit the perception of the affected frequencies (Moore and Glasberg 1997).

Frequency lowering is a well-established alternative to conventional amplification in individuals with severe hearing impairment. In order to restore audibility, high-frequency components are re- produced in a lower frequency range.

There are different frequency-lowering strategies for hearing-impaired individuals in hearing aids such as frequency transposition and frequency compression (Kuk et al. 2009). With regard to frequency transposition, the high-frequency portion of the spectrum is shifted lower by a constant frequency difference and mixed with the original signal. In frequency compression, the bandwidth of the high-frequency components is compressed to fit into a narrower bandwidth and there is no spectral superimposition of the original and the compressed signal. Figure 1:4 displays example input-output functions for frequency transposition and frequency compression.

Frequency-lowering strategies have primarily been developed to increase speech intelligibility and have become an integral feature of hearing-aid signal processing. This feature, however, has not been revised or optimized for music.

31 Chapter 1: Introduction

frequency transposition frequency compression

6 6

fout fout kHz 4 kHz 4

2 2

2 4 6 8 2 4 6 8 fin kHz fin kHz Figure 1:4 Examples of input-output function for frequency transposition and frequency compression.

1.3.3 Research question and rationale Hearing loss is a global problem. According to the World Health Organization (2015), 360 million people worldwide suffer from disabling hearing loss.

The research into the effects of hearing loss and hearing aids has focused primarily on speech intelligibility and has yielded innovative approaches to improve speech perception with hearing aids (e.g., Humes 1991; Levitt 2001; Barreto & Ortiz 2008; Tawfik et al. 2009; Cornelis, Moonen, & Wouters 2012). By contrast, research into the effects on music perception is scarce. Previous research indicates that hearing loss affects various aspects of music perception such as pitch stability, the perception of dissonance, the ability to recognize instruments, and the enjoyment of music (Feldmann & Kumpf 1988; Leek & Summers 2001; Tufts et al. 2005; Neukomm 2006; Leek et al. 2008). State-of-the-art hearing aids do not fully compensate for the hearing impairments regarding music perception and hearing-aid users express a need to optimize their devices for music (Madsen & Moore 2014).

This thesis aims at developing strategies to improve the signal processing of hearing aids for music. To guide the development, further research into the effects of hearing loss and hearing aids on music perception was conducted. The thesis addresses the following three research questions:

(1) How does music perception differ between normal-hearing and hearing-impaired listeners?

(2) How does music perception differ in hearing-impaired listeners with and without hearing aids?

(3) How can hearing aids be optimized for music?

32 Chapter 1: Introduction

1.4 Study Overview

Four studies with a total amount of 115 participants were conducted to investigate the research questions presented above. The first two experiments investigated how hearing loss and hearing aids affect music perception. Based on the findings, a strategy regarding the dynamic compression in hearing aids was developed and successfully validated in the third experiment. In the fourth experiment, a novel strategy for frequency lowering was tested. Each of the chapters 2-5 covers one experiment and was written in the style of a journal manuscript.

Chapter 2 / Experiment 1

This chapter aimed at finding differences in music perception between normal-hearing and hearing- impaired listeners. For this purpose, a music test battery was developed which was able to measure the effect of hearing loss on important dimensions of music. An experiment with 19 normal-hearing and 21 hearing-impaired participants was conducted to investigate the effect of hearing impairment as the independent variable.

Chapter 3 / Experiment 2

This chapter aimed at investigating the effect of hearing aids on music perception. For that purpose, 25 hearing-impaired participants conducted the previously developed music test twice, once with and once without hearing aids.

Chapter 4 / Experiment 3

This chapter aimed at optimizing dynamic compression in hearing aids for music. The dynamic range in music across ten different genres was researched and two optimized compression settings were developed. Thirty-one hearing-impaired participants compared the optimized compression settings to a compression standard (NAL-NL2) as a reference.

Chapter 5 / Experiment 4

In this chapter, a frequency-lowering method for music was developed. The benefit of the novel frequency-lowering approach for music was assessed in a study with 19 hearing-impaired listeners who had not experienced frequency lowering prior to the experiment.

33 Chapter 1: Introduction

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40 Chapter 2: Development of the AMP test

Chapter 2 Development of the Adaptive Music Perception Test

The content in this chapter was published in the journal Ear & Hearing (March-April edition 2015).

Impact Factor: 2.84

Authors: Martin Kirchberger and Frank Russo

Kirchberger, M. J., & Russo, F. A. (2015). Development of the Adaptive Music Perception Test . Ear and Hearing, 36 (2), 217-228.

41 Chapter 2: Development of the AMP test

Abstract

OBJECTIVES. Despite vast amounts of research examining the influence of hearing loss on speech perception, comparatively little is known about its influence on music perception. No standardized test exists to quantify music perception of hearing-impaired (HI) persons in a clinically practical manner. This study presents the Adaptive Music Perception (AMP) test as a tool to assess important aspects of music perception with hearing loss.

DESIGN. A computer-driven test was developed to determine the discrimination thresholds of 10 low-level physical dimensions (e.g., duration, level) in the context of perceptual judgments about musical dimensions: meter, harmony, melody, and timbre. In the meter test, the listener is asked to judge whether a tone sequence is duple or triple in meter. The harmony test requires that the listener make judgments about the stability of the chord sequences. In the melody test, the listener must judge whether a comparison melody is the same as a standard melody when presented in transposition and in the context of a chordal accompaniment that serves as a mask. The timbre test requires that the listener determines which of two comparison tones is different in timbre from a standard tone (ABX design). Twenty-one HI participants and 19 normal-hearing (NH) participants were recruited to carry out the music tests. Participants were tested twice on separate occasions to evaluate test–retest reliability.

RESULTS. The HI group had significantly higher discrimination thresholds than the NH group in 7 of the 10 low-level physical dimensions: frequency discrimination in the meter test, dissonance and intonation perception in the harmony test, melody-to-chord ratio for both melody types in the melody test, and the perception of brightness and spectral irregularity in the timbre test. Small but significant improvement between test and retest was observed in three dimensions: frequency discrimination (meter test), dissonance (harmony test), and attack length (timbre test). All other dimensions did not show a session effect. Test–retest reliability was poor (<0.6) for spectral irregularity (timbre test); acceptable (>0.6) for pitch and duration (meter test), dissonance and intonation (harmony test), and melody-to-chord ratio I and II (melody test); and excellent (>0.8) for level (meter test) and attack (timbre test).

CONCLUSION. The AMP test revealed differences in a wide range of music perceptual abilities between NH and HI listeners. The recognition of meter was more difficult for HI listeners when the

42 Chapter 2: Development of the AMP test listening task was based on frequency discrimination. The HI group was less sensitive to changes in harmony and had more difficulties with distinguishing melodies in a background of music. In addition, the thresholds to discriminate timbre were significantly higher for the HI group in brightness and spectral irregularity dimensions.

The AMP test can be used as a research tool to further investigate music perception with hearing aids and compare the benefit of different music processing strategies for the HI listener. Future testing will involve larger samples with the inclusion of hearing-aided conditions allowing for the establishment of norms so that the test might be appropriate for use in clinical practice.

2.1 Introduction

2.1.1 Motivation Hearing impairment affects the perception of sound leading to reductions in speech intelligibility and the enjoyment of music. Extensive research into the effects of hearing loss on speech intelligibility (e.g., Humes 1991; Barreto & Ortiz 2008) has led to various attempts to improve speech perception through hearing aids (Levitt 2001; Tawfik et al. 2009; Cornelis, Moonen, & Wouters 2012). By comparison, research into the effects of hearing loss on music perception is in its infancy. Hear- ing-impaired listeners – unaided and aided – have specified various ways in which the enjoyment of music is affected: instruments are hard to distinguish, sounds are distorted, and melodies are difficult to recognize (Neukomm 2006; Sarchett 2006; Leek et al. 2008).

There are no standardized tests available that have been designed to assess music perception in individuals with hearing loss adaptively. A large number of music perception tests are specifically designed to assess musicality or the skills of healthy and formally trained individuals (Don, Schellen- berg, & Rourke 1999; Woodruff 1983). Another group of music tests focuses on individuals with cochlear implants (Gfeller et al. 2002; Gfeller et al. 2005; Medel Medical Electronics 2006; Cooper, Tobey, & Loizou 2008; Looi et al. 2008; Spitzer, Mancuso, & Cheng 2008; Kang et al. 2009). The first music perception test battery to be specifically developed for hearing-aid users was the Music Per- ception Test (Uys & van Dijk 2011). This test battery includes eleven subtests that assess perception in four dimensions: rhythm (4 subtests), timbre (2 subtests), pitch (2 subtests), and melody (3 subtests). As the tests are not adaptive, its sensitivity to differences between normal-hearing and hearing-impaired listeners appears to be limited.

43 Chapter 2: Development of the AMP test

2.1.2 Concept Music can be broken down into a core set of components such as meter, harmony, melody, and timbre. Meter is the division of a rhythmic pattern according to equal periods or measures (Limb 2006). Strong and weak beats in the pattern are grouped into larger units (Oh 2008), typically cate- gorized as duple or triple according to whether the measure is organized in groups of 2 or 3 beats. The perception of harmony corresponds to the vertical organization of pitch (Piston 1987). This organization concerns simultaneous pitches as in a chord or in counterpoint. Another important aspect of harmony concerns the sequencing of chords, as in a harmonic progression.

A melody is a linear succession of tones, which is perceived as a single entity (Limb 2006). The succession of tones can be specified with regard to melodic contour and interval size (Davies & Jen- nings 1976). The former refers to the direction of the pitch change (Schubert & Stevens 2006) and the latter refers to its magnitude.

Timbre is often defined as the attribute of auditory perception whereby a listener can judge two sounds as dissimilar using any criterion other than pitch, loudness and duration (ANSI 1960). This definition is somewhat unsatisfactory in that it defines timbre through what it is not rather than what it is (Sethares 2005). An alternative approach to defining timbre uses multidimensional scaling techniques to extract the underlying physical dimensions that contribute to its perception (Grey 1977; McAdams et al. 1995; Krumhansl 1989; Krimphoff, McAdams, & Winsberg 1994). Brightness and attack are two dimensions that have been consistently identified as important using multidimensional scaling techniques (Grey 1977; Wessel 1979; Krumhansl 1989; McAdams & Cunibile 1992; Krimphoff, McAdams, & Winsberg 1994; McAdams et al. 1995). The conclusions regarding a third dimension, however, differ. Within the framework of our study, we have defined a third dimension in accordance with the conclusions of Krimphoff, McAdams, and Winsberg (1994) as spectral irregularity. The spectral irregularity is determined by deviation from linearity in the amplitude envelope of the harmonics. A clarinet would have high spectral irregularity because it lacks energy in the even harmonics. A trumpet tone by contrast would have low spectral irregularity as it pos- sesses odd and even harmonics with a linear spectral roll-off.

2.1.3 Objective We aimed to develop a computerized test that is adaptive and thus capable of assessing music perception in hearing as well as hearing-impaired populations. The Adaptive Music Perception Test (AMP-Test) has been designed to investigate the perception of important music dimensions such as

44 Chapter 2: Development of the AMP test

meter, timbre, harmony, and melody. These mid-level dimensions are constructed from 10 low-level dimensions D1-D10 (Figure 2:1) such as attack, level, and pitch, which may ultimately be modified in a fairly direct manner through changes to the hearing-aid technology. While the assessment is not entirely culturally neutral there is no reason to expect that performance will vary across individuals who primarily consume music in the Western harmonic idiom, regardless of genre preferences. Each test of the battery asks the listener to make a response concerning a mid-level dimension while adaptively manipulating the underlying low-level dimensions, thereby allowing for the determination of the respective low-level discrimination thresholds. Thus, thresholds are determined within a musically relevant framework. We contend that the use of these tests corresponds more directly to functional hearing in music than a conventional assessment of discrimination thresholds.

2.1.4 Hypothesis Survey studies of individuals with hearing loss have revealed a wide range of problems encountered following the onset of hearing loss including melody recognition and level changes (Feldman & Kumpf 1988; Leek et al. 2008). We assume that these subjective impressions of problems can be

Figure 2:1 The mid-level and low-level dimensions of the Adaptive Music Perception test. D1 – D10 indicates dimension 1–10; MCR, melody-to-chord ratio; Sp. Irreg., spectral irregularity.

45 Chapter 2: Development of the AMP test objectively tracked with adaptive listening tests that are presented within a musical framework. We predict that individuals with hearing loss will have higher discrimination thresholds than individuals with normal hearing.

2.2 Materials and Methods

The AMP test comprises 4 subtests including meter, harmony, melody, and timbre discrimination.

2.2.1 General test design Each subtest was designed to determine the discrimination thresholds of two or more low-level physical dimensions. In each trial, one of these low-level dimensions was manipulated so as to in- stantiate the mid-level dimension. For example, the downbeat in the meter subtest could be con- veyed by a difference in level, duration or pitch. The adaptive process of each low-level dimension was interleaved to obscure the structure of the test and to discourage analytic modes of listening.

We pseudo-randomized the position of the correct answer with the constraint that the right answer was equally distributed among both answer buttons.

2.2.2 Adaptation An experimental procedure is adaptive if the selection of the stimuli is determined by the results of the preceding trials (Treutwein 1995). Our motivation for making the AMP test adaptive was to measure performance in a manner that was fast and accurate for all degrees of hearing loss and music ability.

The AMP test applies the transformed two-alternative-forced-choice method (2-AFC) using a 2- down 1-up rule (Levitt 1971), which is commonly used in tests of auditory thresholds (e.g., Jesteadt, Wier, & Green 1977; Wier, Jesteadt, & Green 1977; Moore, Glasberg, & Shailer 1984; Bochner, Snell, & MacKenzie 1988).

The presentation and adaptation of the low-level dimensions in each subtest were interleaved. The adaptation process was stopped once a minimum of 6 reversal points was reached on each dimension. The standard step sizes were halved after the first and second reversals in an effort to acceler- ate the determination of thresholds without compromising accuracy. Discrimination thresholds were calculated by averaging the values of the last 4 reversals.

46 Chapter 2: Development of the AMP test

2.2.3 Sound stimuli Stimuli used across all four subtests were digitally synthesized. A spectrogram of the stimuli is displayed in Figure 2:2. The reference tone that was used for calibration and throughout the tests was a complex tone with the fundamental frequency

= 220 (pitch A3) and 40 harmonics. The starting phases of the 40 harmonics were randomized once and equal for all participants. The amplitude of each harmonic ( = 0,1,…39 ) was attenuated by 2 in relation to the amplitude of the fundamental . The resulting spectral shape corresponds roughly with that of a trumpet tone (Krimphoff et al. 1994). The test stimuli were played back at 40 sensation level (SL) which is consistent with previous psychoacoustic studies (Jesteadt et al. 1977; Wier 1977; Moore et al. 1984; Bochner et al. 1988; Arehart 1994). Figure 2:2 Spectrogram of the AMP test audio stimuli. The reference tone (0 sec - 0.4 sec ) in the calibration, meter subtest, and timbre subtest is followed by the reference cadence of the harmony subtest (0.8 sec - 3.8 sec) and by one example of the melody subtest (4.2 sec – 10.2 sec).

2.2.4 Test procedure The AMP test was implemented in MATLAB R2009a. Before testing with a participant commenced, the hearing thresholds were determined for the reference tone using a 2-AFC process. The presentation level of the reference tone in the test was then individually set for each participant at 40 . On average, the meter and timbre subtests took 10 minutes each, the harmony subtest took 12 minutes and the melody subtest took 11 minutes. Each subtest could be interrupted and continued at any time.

47 Chapter 2: Development of the AMP test

Each subtest was preceded by training trials with feedback to ensure that the task was understood. The initial discrimination differences of the low-level dimensions were made high enough so that the nature of the tasks did not generate confusion. In order to assess test-retest reliability for each subtest, participants were asked to complete testing on two separate sessions.

2.2.5 Meter subtest: level, pitch, and duration A sequence of 6 harmonic tones was played isochronously in each trial. The participant was asked to indicate whether the sequence constituted a duple or triple meter.

The inter-onset interval between isochronous beats was 600 . The upbeats had the spectral characteristics of the calibration tone (fundamental frequency: 220 , roll-off: −2 per harmonic) and a duration of 280 . As mentioned above, the initial phases are defined and originate from a one-time randomization prior to the test development. The downbeats are realized by adaptively introducing a difference from the upbeats with respect to level, pitch, or duration. Corre- spondingly, the dimensions for which thresholds are determined are labeled level (D1), pitch (D2), and duration (D3).

RATIONALE If the inter-onset interval is lower than 100 , listeners perceive a sequence of tones as a single, continuous event. For intervals greater than 1.5 , grouping gets more difficult as the sounds seem disconnected (Fraisse 1978). In between these two limits, the distance of two events is over- estimated for small intervals and underestimated for bigger intervals. The point of subjective equal- ity, where subjective judgments corresponded to the objective duration, is reached at approximately 600 (Krumhansl 2000).

The sensation of pulse is also most salient for intervals of 600 (Parncutt 1994). To increase the sensitivity of the meter subtest, we therefore chose to use an inter-onset interval of 600 .

The perceived meter of a sequence is generally established quite early after a couple of beats (Parncutt 1994). With regard to the test design, it is beneficial to keep the test duration short in order to avoid fatigue. In the meter subtest, only 6 beats are played back in each trial. This is the least common multiple of duple (two) and triple (three) meter and allows for three or two full measures respectively. According to participants' feedback in the pilot study, 6 beats are sufficient to detect the meter if the downbeat is audible.

48 Chapter 2: Development of the AMP test

2.2.6 Harmony subtest: dissonance and intonation Two cadences composed of 3 dyad chords (root note and fifth) were played back in succession: subdominant (IV), dominant (V), and tonic (I) (Figure 2:3). The participants were asked to indicate the cadence that appeared to be less resolved. The reference cadence was perfectly in tune, the second cadence was detuned.

We used just intonation to define the frequencies of the reference cadence: the ratios of two notes in any interval were defined by the harmonic series and are related by small whole numbers. The frequency ratio of the root note and the fifth of every dyad was 3: 2, such that the respective harmonics co-

Figure 2:3 The subdominant (IV), dominant (V) and tonic (I) incide. Had we used equal temperament, the dyad of the harmony subtest. frequency ratio of the root note and the fifth would be √2) = 1.4983 , and thus the harmonics would not coincide (Figure 2:4). The frequency ratio between the subdominant and the tonic was 4: 3.

The root note of every dyad was composed of 6 harmonics with a roll-off factor of −2 per harmonic. The fifth of every dyad was composed of 4 harmonics with a roll-off factor of −3 per harmonic. The first harmonic of the fifth was attenuated by 1 compared to the first harmonic of the root note. By this means, the coinciding harmonics (root: harmonic 3 / fifth: harmonic 2, root: harmonic 6 / fifth: harmonic 4) were equal in amplitude. The initial phases of all harmonics were pseudo-randomized with the provision that coinciding harmonics differed by 120° .

In one of the two cadences, the tonic dyad was manipulated in one of two different ways: either the pitch of the fifth was increased or the pitch of the whole dyad was shifted. In the first case, the vertical structure of the tonic dyad was detuned causing higher sensory dissonance (Terhardt 1984; Tufts, Molis, & Leek 2005). In the second case, the vertical structure of the tonic dyad was in tune; however, the presented pitch did not correspond to the expected pitch in the given tonality (Piston 1987; Krumhansl 1990; Lerdahl 2001). The adaptive modifications that were applied to the pitch of the last dyad were within the bounds of a semitone. Thus, the basic meaning of the cadence was preserved (Blackwood 1985) and the pitch modifications implied a change in intonation. According-

49 Chapter 2: Development of the AMP test ly, the dimensions for which thresholds were determined in the harmony subtest were labeled dissonance (D4) and intonation (D5).

Figure 2:4 A schematic plot of the harmonic spectrum of the root note and the fifth in just intonation or equal temperament. Deviations are exaggerated for better visibility.

2.2.7 Melody subtest: melody-to-chord ratio Two 4-note melodies were played back and accompanied by a harmonic chord, which served as a mask. The task was to identify whether the contours of the two melodies were the same or different. The two melodies presented during the trial always started on different pitches (i.e., second melody was transposed).

50 Chapter 2: Development of the AMP test

The transposition (pitch shift by constant interval) of the melodies was implemented to ensure that focusing on absolute pitches could not circumvent the melody recognition task. If the contours of the two melodies were the same, the second melody would be a copy of the first melody chromati- cally transposed by one whole tone. The contour of either the first or the second melody was made different by interchanging the second and the third tone of the respective melody.

Two sets of melodies, a lower and a higher one were included in the subtest. The two sets as well as the accompanying A-major and G-major chords are depicted in Figure 2:5.

Figure 2:5 Two examples of the melody subtest. The upper bars depict two melodies from melody set 1 that have the same contour (up-down-up). The lower bars depict two melodies from melody set 2 that have a different contour (down-up-down; up-down-up).

During the subtest, the sound level of the chords was kept constant and the levels of the melodies were adapted. For both melodies, the melody-to-chord ratios were determined indicating the point at which the melodies were perceptually masked by the chords. The dimensions are labeled MCR I (D6) and MCR II (D7) correspondingly.

2.2.8 Timbre subtest: brightness, attack, and spectral irregularity Three tones were played back in succession. Participants were asked to decide whether the third tone sounded like the first or the second (ABX design).

STIMULI DESIGN

The tones differed in one of the three timbral dimensions: rapidity of attack, brightness, or spectral fine structure (Krimphoff et al. 1994). The deviations were introduced to a standard tone that matched the calibration tone in its spectral characteristics: the fundamental frequency ( 220 ), the number of harmonics (40) including the initial phases, and the roll-off factor ( −2 ). The duration of the tones was set to 1 . For the purposes of this test, attack was defined by the duration of the linear fade-in, brightness by the roll-off factor of the spectrum, and spectral irregularity by

51 Chapter 2: Development of the AMP test extent of attenuation in the even harmonics (Krimphoff, McAdams, & Winsberg 1994; Jensen 2002). The dimensions of the timbre subtest were labeled brightness (D8), attack (D9), and spectral irregularity (D10).

STIMULI CALIBRATION

In order to avoid perceptual interactions between the underlying low-level dimensions, a calibration session preceded the timbre subtest. The participant had to equalize the loudness of the standard tone with calibration tones covering the expected range of the difference values of the respective dimensions that are adapted in the test. By means of interpolation, the necessary amplification was calculated and applied to the modified tones before being played back. By this means, we intended to minimize loudness differences so that the presented tones were primarily distinguished by timbral characteristics.

2.2.9 Music experience Each participant completed a questionnaire to assess years of musical training, listening and per- forming habits as well as a self-assessment of their musicality (Table 2:1, column 1 and 2). Points were allocated according to the answers (Table 2:1, column 3) and weighted with respect to their relative importance. For example, years of music training was deemed most important and thus received the greatest weight (Kang et al. 2009). The points were then summed to determine an overall measure of music experience (ME). The range and average of the normal-hearing participants was [−3; 4] and 0.32 respectively; the range and average of the hearing-impaired participants was [−3; 4] and 0.21 respectively. A t-test confirmed that the two groups did not differ with regard to ME: , = 0.023, = 0.881 .

2.2.10 Participants Nineteen normal-hearing participants (P1-P19) and 21 hearing-impaired participants (P20-P41) were recruited for this study (Table 2:2). Degree of hearing loss was determined according to the American Speech-Language-Hearing Association (i.e., average value of the hearing thresholds at 0.5 , 1 , 2 , and 4 across both ears). Participants with hearing loss less than 25 were assigned to the normal-hearing group, participants with hearing loss greater than or equal to 25 were assigned to the hearing-impaired group. All audiometric data was assessed within 1 year of the test date. The age of the normal-hearing participants ranged from 27 to

52 Chapter 2: Development of the AMP test

67 years (M = 47.8 years), whereas the age of the hearing-impaired participants ranged from 38 to 83 years (M = 64.7 years). As expected, the age difference between both groups was statistically significant: = 4.15, < 0.001 .

Table 2:1 The music questionnaire (column 1 and 2) and the respective points allocation (column 3) to determine an objective music experience (ME) measure for each participant.

Question Answer Allocated

points

1 How many years of music training have you received? <1 yr -2 a) Please indicate your instrument/voice training 1-3 yrs -1 b) Please indicate your music theory or ear training 3-10 yrs 0 c) Please indicate if and how long you have ever taught your- >10 yrs 1 self to play an instrument? (Answer accumulated) professional 2

musician

No 0 Are you currently active musically (i.e., within the last year)? Yes 1

No -0.5

Do you consider yourself musical? Somewhat 0

Yes 0.5

<1 hr -0.5

How many hours do you listen to music (average per day)? 1-3 hrs 0

>3 hrs 0.5

2.3 Results On each low-level dimension D1-D10, a two-factor analysis of covariance (ANCOVA) was performed. The between-subjects factor (independent variable) was the hearing loss group (NH, HI). Music experience (ME) was entered as the covariate. The results are shown in Table 2:3. In addition, test- retest reliability was assessed using interclass correlation.

53 Chapter 2: Development of the AMP test

Table 2:2 Characteristics of the test participants: sex, audiometric data, degree of hearing loss (HL) as defined by ASHA, music experience (ME), and age.

Left Ear Right Ear Participant Sex 0.5k 1k 2k 4k 0.5k 1k 2k 4k HL ME Age P1 m -10 -5 0 -5 -10 0 -5 -5 -5.0 -1 28 P2 m -5 -5 -5 0 0 0 0 -5 -2.5 2 27 P3 m 0 -5 0 -5 -5 -5 -5 10 -1.9 1 30 P4 m 0 0 -5 0 0 0 0 5 0.0 -1 33 P5 m 5 5 0 10 10 0 -5 -5 2.5 -2 50 P6 m 5 5 5 0 5 5 5 0 3.8 -1 36 P7 f 0 0 0 10 5 5 10 10 5.0 0 51 P8 m 5 5 10 10 0 0 10 5 5.6 2 33 P9 m 5 0 5 20 5 5 0 15 6.9 2.5 51 P10 m 5 5 15 15 5 0 10 5 7.5 4 45 P11 m 15 5 5 15 10 5 5 20 10.0 1.5 47 P12 m 10 10 10 40 5 5 5 20 13.1 3 59 P13 m 15 10 15 15 15 5 15 25 14.4 -2 45 P14 m 5 0 5 25 15 5 10 60 15.6 -0.5 67 P15 m 5 5 25 30 5 5 25 30 16.3 2 63 P16 m 20 15 15 30 20 20 15 35 21.3 -2 55 P17 m 0 5 25 70 5 5 20 50 22.5 0 65 P18 m 5 5 10 65 10 10 15 65 23.1 0.5 67 P19 m 15 20 20 45 10 15 20 40 23.1 -3 57 P20 m 5 15 35 60 10 10 30 50 26.9 -1 61 P21 m 15 15 35 45 10 25 30 45 27.5 3 66 P22 m 15 15 20 60 15 20 20 60 28.1 2 51 P23 m 5 5 30 70 5 5 60 75 31.9 -2 68 P24 m 20 20 30 60 20 25 35 50 32.5 -0.5 68 P25 m 20 30 45 50 20 30 40 55 36.3 3.5 76 P26 m 30 20 55 75 30 20 5 60 36.9 1 63 P27 f 40 40 30 45 45 40 25 30 36.9 0 45 P28 m 25 30 40 50 25 35 35 55 36.9 -2.5 69 P29 m 5 0 0 45 45 65 75 65 37.5 4 76 P30 f 30 35 40 30 30 35 50 50 37.5 2.5 74 P31 m 30 40 50 60 30 35 45 45 41.9 -0.5 77 P32 m 50 50 60 85 15 15 25 45 43.1 -3 64 P33 m 15 30 60 70 10 35 60 70 43.8 1 73 P34 m 45 50 45 55 40 40 35 45 44.4 -1.5 47 P35 m 5 15 45 75 15 50 70 85 45.0 -3 38 P36 m 25 35 55 60 25 30 55 80 45.6 -2.5 64 P37 f 45 55 70 85 25 35 40 50 50.6 3.5 68 P38 m 50 60 60 50 45 60 60 55 55.0 1 50 P39 m 55 55 60 55 55 65 65 65 59.4 -1.5 77 P40 m 55 65 65 80 50 55 65 75 63.8 1 83

The NH and HI group not only differed in hearing loss but also in age. To account for this age difference, we ran a forced-entry multiple regression analysis with age, hearing loss, and music experience as independent variables. Test results are displayed in Table 2:4. Because of the correlation of the predictor variables HL and AGE in the multiple regression analysis, we performed a multicolline-

54 Chapter 2: Development of the AMP test arity diagnostic. Kutner, Nachtsheim, and Neter (2004) proposed values above 10 as critical. In all four subtest data sets, the variance inflation factor values were smaller than 2.5. Thus, we can assume that multicollinearity does not play a role in the multiple regression analysis of our test data.

Table 2:3 Results of the repeated measure ANCOVA analysis for each dimension of the tests. The condition hearing loss was the dependent variable, music experience (ME) the covariate.

Hearing Loss Music Experience Session effect Hearing Loss x Session

= 1.95 = 9.09 = 2.21 = 0.68 D1: Level , , , , = 0.170 = 0.005 = 0.146 = 0.414 = 15 .57 = 6.033 = 9.62 = 2.97 D2: Pitch , , , , < 0.001 = 0.019 = 0.004 = 0.093 = 1.11 = 1.87 = 0.51 = 0.098 D3: Duration , , , , = 0.300 = 0.180 = 0.480 = 0.756 = 4.87 = 1.41 = 4.50 = 0.511 D4: Dissonance , , , , = 0.035 = 0.244 = 0.042 = 0.480 = 8.63 = 4.26 = 3.78 = 0.013 D5: Intonation , , , , = 0.006 = 0.047 = 0.061 = 0.911 = 7.87 = 0.58 = 0.05 = 0.005 D6: MCR I , , , , = 0.010 = 0.455 = 0.824 = 0.945 = 10 .29 = 1.93 = 1.95 = 0.156 D7: MCR II , , , , = 0.004 = 0.178 = 0.175 = 0.697 = 7.43 = 0.034 = 0.764 = 0.001 D8: Brightness , , , , = 0.010 = 0.856 = 0.388 = 0.971 = 1.16 = 3.77 = 4.80 = 0.495 D9: Attack , , , , = 0.289 = 0.060 = 0.035 = 0.486 = 5.98 = 1.88 = 1.78 = 0.383 D10: Spect. Irreg. , , , , = 0.019 = 0.180 = 0.190 = 0.540

With the exception of results that are of particular theoretical interest, only those results that reached significance are reported.

2.3.1 Meter subtest All 19 NH and 21 HI participants completed the meter subtest in both session. Figure 2:6 depicts the results obtained for level (D1), pitch (D2), and duration (D3) as boxplots.

The normal-hearing group performed better on D2 (pitch): , = 15.57, < 0.001 . The hearing- impaired group performed marginally better on D1, however, this trend did not reach significance:

55 Chapter 2: Development of the AMP test

, = 1.95, = 0.170 .

The ANCOVA revealed a significant effect of ME on D1, , = 9.09, = 0.005 and D2, , =

6.033, = 0.019 , but not on D3, , = 1.87, = 0.180 .

Table 2:4 Forced-entry multiple linear regression for each dimension. Predictors were hearing loss (HL), age, and music experience (ME).

R2adj P pHL βHL PAGE βAGE PME βME D1 0.255 0.003 0.114 -0.323 0.829 0.044 0.001 -0.508 D2 0.420 0.000 0.008 0.498 0.510 0.666 0.014 -0.329 D3 -0.026 0.573 0.729 -0.082 0.389 -0.206 0.225 -0.210 D4 0.044 0.234 0.349 0.228 0.735 0.081 0.322 -0.189 D5 0.445 0.000 0.010 0.499 0.657 0.081 0.020 -0.352 D6 0.289 0.011 0.034 0.565 0.834 0.054 0.985 -0.003 D7 0.388 0.002 0.003 0.777 0.296 -0.251 0.222 -0.197 D8 0.227 0.007 0.288 0.215 0.076 0.371 0.830 -0.032 D9 0.038 0.230 0.629 0.108 0.784 0.062 0.078 -0.304 D10 0.122 0.056 0.181 0.290 0.671 0.092 0.128 -0.249

A session effect was observed on D2 , = 9.62, = 0.004. The interclass correlations were 0.904 (D1), 0.753 (D2), and 0.739 (D3). The multiple regression confirms a significant effect of hearing loss on pitch discrimination (D2: ). The multiple regression also con- = 0.008 , β = 0.498

Figure 2:6 Box-plot (median, quartiles, whiskers: 1.5 x IQR, & individual data points) showing the level D1 (dB), the pitch D2 (Hz), and the duration D3 (sec) thresholds of the meter subtest by group and session. (1 NH_t: normal - hearing / test sesssion, 2 NH_r: normal-hearing / retest session, 3 HI_t: hearing-impaired / test session, 4 HI_r: hea r- ing-impaired / retest session).

56 Chapter 2: Development of the AMP test firms music experience as a significant factor for level discrimination (D1: = 0.001 , β = and pitch discrimination (D2: ). −0.508) = 0.014 , β = −0.329

2.3.2 Harmony subtest Four NH participants and 2 HI participants were excluded. One NH participant was excluded because they did not understand the task even after extensive training. Three NH participants could not complete either the test or the retest because of scheduling conflicts. Two HI persons indicated that their power of concentration had decreased over the course of testing.

Fifteen normal-hearing participants and 19 hearing-impaired participants conducted the harmony subtest in both sessions. Figure 2:7 depicts the results obtained for dissonance (D4) and intonation (D5) as boxplots. Normal-hearing participants outperformed hearing-impaired participants on D4,

, = 4.87, = 0.035, and D5, , = 8.63, = 0.006 .

Music experience was positively related to performance on D5: , = 4.26, = 0.047 . The effect of sessions was significant on D4, , = 4.50, = 0.042 . The interclass correlations were 0.805 (D4) and 0.824 (D5). The multiple regression reaffirms a significant effect of hearing loss and music experience on intonation (D5: = 0.010 , β = −0.499 ; = 0.02 , β = −0.352 ).

Figure 2:7 Box-plot (median, quartiles, whiskers: 1.5 x IQR, & individual data points) showing the dissonance D4 (Hz) and the intonation D5 (Hz) thresholds of the harmony subtest by gro up and session. (1 NH_t: normal-hearing / test sesssion, 2 NH_r: normal-hearing / retest session, 3 HI_t: hearing-impaired / test session, 4 HI_r: hearing-impaired / retest session).

57 Chapter 2: Development of the AMP test

2.3.3 Melody subtest Five normal-hearing participants and 7 hearing-impaired participants were excluded because they found the task too challenging. These participants could not detect reliably whether the melodies were different even in the absence of background noise.

Fourteen normal-hearing participants and 14 hearing-impaired participants completed the melody subtest in both sessions. Figure 2:8 depicts the melody-to-chord ratios obtained for both melody sets (D6 and D7) as boxplots. Hearing-impaired participants performed worse in melody set I,

, = 7.87, = 0.010 and melody set II, , = 10.29, = 0.004 . There were no significant effects of ME or session. The interclass correlations were 0.809 (D6) and 0.838 (D7). The multiple regression confirmed a significant effect of hearing loss on both melody-to-chord ratios (D6: ; D7: ). = 0.034 , β = −0.565 = 0.003 , β = −0.777

58 Chapter 2: Development of the AMP test

2.3.4 Timbre subtest One NH person was excluded because the participant could not conduct the retest session due to a scheduling conflict. Eighteen NH and 21 HI participants completed the timbre subtest in both sessions. Figure 2:9 depicts the discrimination thresholds obtained for brightness (D8), attack (D9), and spectral irregularity (D10) as boxplots. Normal-hearing participants outperformed hearing-impaired

participants on D8, , = 7.43, = 0.010 and D10, , = 5.98, = 0.019 . The effect of session

was significant on D9, , = 4.80, = 0.035. The interclass correlations were 0.821 (D8), 0.937 (D9), and 0.712 (D10). The multiple regression analysis did not yield any significant results.

Figure 2:9 Box-plot (median, quartiles, whiskers: 1.5xIQR, & individual data points) showing the b rightness D8 (dB), attack D9 (sec), and spectral irreguliarity D10 (dB) thresholds of the timbre subtest by group and session. (1 NH_t: normal-hearing / test sesssion, 2 NH_r: normal-hearing / retest session, 3 HI_t: hearing-impaired / test session, 4 HI_r: hearing-impaired / retest session).

2.4 Discussion We have developed an adaptive music perception test for hearing-impaired listeners. Test results of the AMP test showed a significant impact of hearing loss on the perception of important musical aspects such as meter, harmony, melody, and timbre.

In 7 of the 10 adapted underlying low-level dimensions, the ANCOVA revealed that HI participants performed significantly worse than their NH counterparts: pitch (D2, meter subtest), dissonance (D4, harmony subtest), intonation (D5, harmony subtest), melody-to-chord ratio I (D6, melody sub-

59 Chapter 2: Development of the AMP test test), melody-to-chord ratio II (D7, melody subtest), brightness (D8, timbre subtest), and spectral irregularity (D10, timbre subtest). There was no significant effect of hearing loss on level (D1, meter subtest), duration (D3, meter subtest), or attack (D9, timbre subtest). After taking age into account using a multiple regression approach to analyses, hearing loss remained a significant factor in pitch discrimination (D2, meter subtest), intonation (D5, harmony subtest), and melody detection (D6&D7, melody subtest).

The next section of the discussion considers thresholds obtained for each low-level dimension and how they compare to existing findings obtained using conventional threshold testing – i.e., threshold tests that are not embedded in a musical task as they are here.

2.4.1 D1: Level, meter subtest Jesteadt, Wier, and Green (1977) used sinusoidal tones to determine level discrimination thresholds. An average threshold of 1 was obtained for normal-hearing participants at 40 . As in other studies (Schacknow & Raab 1973; Penner et al. 1974; Fasti & Schorn 1981), the threshold was found to be independent of frequency. In the current study, the stimuli were also presented at a sensation level of 40 and we obtained an average threshold of 1.5 for NH participants and 1.2 for HI participants. The slightly larger thresholds obtained in the current study are likely due to the use of complex tones and the presentation of a stimuli within a musical task.

Several authors have proposed that level discrimination should be better in hearing-impaired listeners because of recruitment and abnormal loudness growth (Luscher & Zwislocki 1949; Denes & Naunton 1950). Findings on this question, however, have been mixed. Fasti and Schorn (1981) investigated level discrimination thresholds of HI listeners with different kinds of hearing disorders such as conductive, noise-induced presbycusis at two distinct frequencies 400 and 5 . In all groups, average thresholds were higher than those of the NH control group. In our study, the average level threshold of the HI group was marginally smaller than the threshold of the NH group but it did not reach significance, due in part to large individual variability that is typically found in level discrimination tasks (Rabinowitz et al. 1976; Houtsma, Durlach, & Braida 1980).

2.4.2 D2: Pitch, meter subtest Several psychophysical studies of complex-tone pitch discrimination have shown that discrimination thresholds in NH listeners are lower than they are in HI listeners. (Hoekstra & Ritsma 1977; Hoeks- tra 1979; Horst 1987; Moore & Glasberg 1988, 1990; Moore & Peters 1992). Discrimination thresh-

60 Chapter 2: Development of the AMP test olds for NH listeners range from 0.2 0.1%) (Hoekstra 1979) to 1.7 0.85%) (Moore & Pe- ters 1992) depending on the method. The results of our study are comparable with an average discrimination threshold of 1.0 0.45%) for NH listeners and 1.8 0.8%) for HI listeners. Never- theless, some caution is advisable in the use of the pitch discrimination dimension of the meter subtest given the significant session effect.

2.4.3 D3: Duration, meter subtest A trend was observed for the average discrimination threshold of the HI listeners to be larger than that of the NH listeners. The trend, however, was not significant. These results align with Ruhm et al. (1966) who concluded that hearing impairment has no effect on the discrimination of acoustic signals on the basis of duration. Tyler et al. (1982), however, found that duration discrimination was generally poorer in HI than in NH listeners. Bochner, Snell, & MacKenzie (1988) conducted experiments to compare the temporal sensitivity of NH and HI listeners for static and transient sounds. Depending on the type of sound, conclusions regarding duration discrimination thresholds vary. Whereas normal-hearing listeners performed significantly better for static sounds shorter than 125 , the groups did not differ for transient sounds or static sounds longer than 200 . Our experiment falls into the latter category given that it utilized static sounds with a minimum duration of 280 . Like Bochner, Snell, & MacKenzie (1988), hearing loss did not have a significant effect on discrimination thresholds for duration.

2.4.4 D4: Dissonance, harmony subtest Discrimination thresholds for dissonance were significantly larger for HI than for NH listeners according to the ANCOVA analysis. This finding is consistent with results reported by Tufts, Molis, & Leek (2005). Stimuli in the Tufts, Molis, & Leek (2005) study resembled those used in the current study, i.e., dyads composed of complex tones with 5 to 6 harmonics. The discrimination thresholds in our study were remarkably small: the average thresholds for HI and NH were 0.16 and 0.08 , respectively. The detection of beats due to amplitude modulation accounts for these thresholds. We use natural tuning for the reference dyad, i.e., the frequency ratio between the fifth and the root is 2:3 and the harmonics completely coincide. Thus, the dyad is very sensitive to modifications compared to a dyad in equal temperament whose harmonics do not coincide (c.f. Figure 2:4).

The forced-entry multiple regression analysis, however, does not reveal a significant effect of hearing loss on the perception of dissonance in the test results. On the basis of this result and the signif-

61 Chapter 2: Development of the AMP test icant session effect, we would advise caution in the interpretation of the test results from the dissonance dimension (D4).

2.4.5 D5: Intonation, harmony subtest Sensitivity to intonation seems to be adversely affected by hearing loss. The HI group had significantly larger thresholds than the NH group and the multiple regression analysis revealed hearing impairment as the main predictor of the intonation thresholds. We assume that the reduction in sensitivity stems from poorer F0 discrimination (Moore & Peters 1992).

2.4.6 D6 & D7: melody-to-mhord ratio I & II (MCR I & II), melody subtest Thirty percent of the participants were not able to carry out the melody subtest. For those participants who were able to do so, hearing loss had a detrimental effect. The average melody-to-chord ratio of the HI group was 5 (MCR I) and 6 (MCR II) higher than the NH group. This outcome appears to be compatible with speech-in-noise thresholds. Listeners with moderate hearing loss ( 40 to 60 ) have SNR losses between 2 and 20 (Killion et al. 2004). Because poorer frequency selectivity contributes to more masking (Moore 2003), hearing-impaired listeners need higher melody-to-chord ratios than their normal-hearing counterparts.

2.4.7 D8: Brightness, timbre subtest The hearing-impaired group was less sensitive to changes in brightness than the normal-hearing group. The multiple regression analysis revealed the same trend, but did not yield a significant impact of hearing impairment on brightness perception. Emiroglu (2007) also conducted experiments comparing brightness perception of NH and HI listeners. The JNDs of listeners possessing hearing loss with steep slope were significantly higher than the JNDs of NH listeners. HI listeners possessing a flat or shallow slope also had higher JNDs but the trend did not reach significance. Nevertheless, Emiroglu (2007) also observed cases where HI listeners performed better than NH listeners. Accord- ing to her theory, the internal representation of brightness can be enlarged due to recruitment so that smaller differences may be perceived more easily. While recruitment may contribute positively to brightness perception, the broadening of auditory filters in hearing-impaired listeners should detract (Leek & Summers 1993).

2.4.8 D9: Attack, timbre subtest Hearing loss does not seem to impact the discrimination of attack. Like duration (D3), attack has a temporal component in that we modify attack by adapting the attack time. However, it differs from

62 Chapter 2: Development of the AMP test

D3 in that a change in duration also implies a change in the steepness of the loudness curve. There- fore, it may be assumed, that a higher sensitivity to loudness changes might increase the sensitivity to attack length. Consequently, this might lead us to expect that a hearing-impaired person with smaller level discrimination thresholds would also perform better in this dimension. However, the variability in the data is quite high and the expected trend is not evident.

2.4.9 D10: Spectral irregularity, timbre subtest The HI listeners were significantly less sensitive to changes in spectral irregularity than their NH counterparts. We attribute this difference to reduced frequency selectivity (Oxenham & Bacon 2003). The multiple regression analysis, however, did not yield a significant effect for hearing loss. Thus it remains possible that the effect of hearing impairment was driven by age differences across the groups.

The results of this investigation show that music experience (ME) had a positive effect on a subset of the dimensions tested. Music training requires the listener to become sensitive to subtle changes in loudness and pitch. Therefore, it is quite understandable that the effect of music experience was significant in the level (D1) and pitch (D2) dimensions of the meter subtest as well as the intonation dimension (D5) of the harmony subtest. The quality of the test or the statements regarding the effect of hearing loss, however, are not compromised by this effect of ME. First, both the ANCOVA analysis and the multiple regression analysis separate the effect of music experience from the effect of hearing loss. More importantly, these tests are designed to be used to assess different hearing- aid algorithms for their applicability for music processing. For instance, we intend to improve the gain model for hearing aids and evaluate the benefit of new designs and parameterizations by using the AMP test. Therefore, under typical use, the results will be analyzed within and not between subjects. We acknowledge that the sample recruited for this study was not ideal. In particular, the age difference between groups limits the interpretability of the ANCOVA results. However, the regression analysis indicates that hearing loss independently contributed to variance in four of the test dimensions (D2, D5, D6, D7). Moreover, the proportion of variance accounted for by hearing loss in these dimensions was larger than that accounted for by age.

Test-retest reliability was excellent (>.8) for 2 out of 10 dimensions: level (D1) and attack (D9). Ac- ceptable test-retest reliability (>.6) was found in 7 out of 10 dimensions: pitch (D2), duration (D3),

63 Chapter 2: Development of the AMP test dissonance (D4), intonation (D5), MCR I & II (D6&D7), and brightness (D8). Poor test-retest reliability (<.6) was only found for spectral irregularity (D10).

In retrospect, it seems that extending our training session would have been beneficial, leading to fewer instances of significant differences between test and retest. We observed a significant session effect for the dimension pitch (D2), dissonance (D4), and attack (D9). With regard to pitch, we assume that the fact that the meter subtest is conducted first, might contribute to the session effect. The participants are not used to a laboratory environment and they might be distracted and nerv- ous in the beginning. Level (D1) and duration (D3) of the meter subtest, however, did not show a session effect. We therefore assume that pitch (D2) needs longer training or even an additional training session beforehand to minimize practice effects. With regard to dissonance (D4), we assume that participants need more time to fully grasp the task that the dissonant chord is less resolved. Again, more training might help to get the participants more familiar with the task even in the first session. Regarding attack (D9), we assume that it might not have been obvious for each participant in the first session, that this dimension is part of timbre perception. It differs from the other two timbre dimensions – brightness (D8) and spectral irregularity (D10) – in that it focuses on the temporal aspect rather than the spectral aspect of the stimuli.

To minimize a potential session effect, we advise to counterbalance the presentation order of the different conditions under test. If AMP is used to compare the benefit of two algorithms for music perception, half of the participants should start with algorithm 1, the other half with algorithm 2.

Future versions of this test may reduce the number of subtests so as to focus on those dimensions that are most relevant to music listening with an impairment and to make administration of the test more time-efficient. On the basis of the current results, it seems that the duration dimension in the meter subtest and the attack dimension in the timbre subtest may be expendable. Neither dimension is affected by hearing loss. As a consequence of cutting these dimensions, the meter and timbre subtest would also become shorter allowing for more reversals to establish thresholds. Addi- tional reversals should help to make thresholds more precise and to reduce test-retest variability.

We acknowledge that the melody subtest may be challenging for a significant proportion of individuals. Nevertheless, it is certainly an interesting tool for those who are very concerned with music. The main difficulty for those who could not grasp the task was to understand the concept of transposition. Future use of this test might circumvent the problem by omitting the transposition. We

64 Chapter 2: Development of the AMP test introduced this concept to ensure that participants did not focus on absolute pitches but listened to the melody as a whole.

We assume that the state-of-the-art hearing-aid signal processing is not optimal for music listening as it is designed to improve speech intelligibility. At various points in the signal-processing chain, we imagine that simple changes could be made to improve music processing. The gain model, for example, might be optimized to enhance the perception of timbre by emphasizing spectral differences. Neighboring bands of the filter bank could be steered less independently to allow the preservation of spectral contrast. The compression ratio and the time constants – attack and release – of the gain model decisively change the perception of the attack of a signal. Level changes are also inherently modified by the compression ratios. Pitch / F 0 discrimination is enhanced if audibility, especially of the higher frequencies, is ensured (Arehart 1994). The AMP test may be used to systematically assess the efficacy of these types of changes in signal-processing strategy.

We developed an adaptive test battery that assesses the perception of important music aspects such as meter, harmony, melody, and timbre objectively. We were able to reveal differences in music perception between hearing-impaired and normal-hearing participants. The AMP test can be used as a research tool to further investigate music perception with hearing aids and compare the benefit of different music processing strategies for the hearing-impaired listener. Future testing will involve larger samples with the inclusion of hearing-aided conditions allowing for the establishment of norms so that the test might be appropriate for use in clinical practice.

Acknowledgments

The research protocol for this study was approved by grant (EK 2013-N-19) from the Ethics Commis- sion of the ETH Zurich.

This research was supported by Phonak AG.

The authors declare no other conflict of interest.

65 Chapter 2: Development of the AMP test

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70 Chapter 3: Music Perception: Aided vs. Unaided

Chapter 3 Music Perception in Aided and Unaided Hearing-Impaired Listeners

Abstract

Hearing-impaired listeners suffer from impaired music perception. A study was conducted in which participants performed music tests related to meter, harmony, and timbre perception both with and without hearing aids. Performance in the meter and timbre subtests was worse when participants wore hearing aids. Dynamic compression in hearing aids was found to be a factor which significantly affects the perception of timbre. The results advocate less dynamic compression in hearing aids for music.

3.1 Introduction Hearing loss affects the perception of music in various ways. Pitch perception of complex sounds is generally weaker and less stable in hearing-impaired (HI) listeners (Larkin 1983; Leek & Summers 2001). Tufts, Molis, and Leek (2005) found out that HI participants are less sensitive to differences between consonance and dissonance. Kirchberger and Russo (2015) measured poorer discrimination in HI listeners in musical tasks related to meter, harmony, melody, and timbre perception. In addition, surveys revealed that a large proportion of HI listeners have difficulty recognizing melodies and in distinguishing instruments (Feldmann & Kumpf 1988; Neukomm 2006).

Surveys have revealed that there are numerous problems when using hearing aids for music listening. In a study by Leek et al. (2008) with 68 participants, almost half of the participants complained about music being either too loud or too soft overall. Thirty-four percent reported problems with the volume changes in music processed through HA. Sixty-five percent indicated difficulty understanding words in songs and one in six experienced challenges in recognizing melodies. In a recent

71 Chapter 3: Music Perception: Aided vs. Unaided survey with 523 participants by Madsen and Moore (2014), similar problems were reported: 72% were not comfortable with the volume of the amplified music in general. Thirty-three percent of the participants referred to problems with acoustic feedback, 29% indicated that their HAs worsened the sound quality of music, 21% found the sound too shrill, 19% reported hearing the music less clearly and 18% thought that HA made it more difficult to hear out individual instruments.

Experimental studies investigating potential improvements of hearing aids for music perception have focused on dynamic compression and frequency lowering. With regard to dynamic compression, the majority of studies indicate that hearing-impaired listeners preferred linear over compressive parameterizations of hearing aids (van Buuren, Festen, & Houtgast 1999; Hansen 2002; Davies- Venn, Souza, & Fabry 2007; Arehart, Kates, & Anderson 2011; Higgins, Searchfield, & Coad 2012; Croghan, Arehart, & Kates 2014). With regard to frequency lowering, the experimental data does not show an explicit benefit of frequency lowering strategies for music perception (Uys et al. 2012; Parsa et al. 2013; Brennan et al. 2014).

As previous evidence has shown, HI patients face diverse problems when listening to music with hearing aids. The surveys, however, could only assess the symptoms rather than the cause of impaired music perception. Further research is necessary to investigate which underlying mechanisms of music perception are affected by hearing aids. This study therefore aims to assess how the use of hearing aids influences the perception of important musical dimensions and intends to identify potential causes.

3.2 Materials and Methods

3.2.1 Participants Twenty-five hearing-aid users were recruited from Toronto, Canada. Table 3:1 shows the participants’ sex, air conduction thresholds, degree of hearing loss, music experience, age, and hearing aids. The degree of hearing loss was determined according to the American Speech-Language- Hearing Association (i.e., average value of the hearing thresholds at 0.5 , 1 , 2 , and 4 across both ears). Music experience was determined according to Kirchberger and Russo (2015).

72 Chapter 3: Music Perception: Aided vs. Unaided

Table 3:1 Characteristics of the test participants: sex, audiometric data, hearing loss (HL), music experience (ME), age, and hearing aid (CR: compression ratio).

Left Ear Right Ear Hearing Aid Participant Sex 0.5 1 2 4 0.5 1 2 4 HL ME Age Brand Model CR P1 f 30 25 25 50 20 25 15 50 30 -1 76 Oticon VPRHS, ITE 1.16 P2 f 40 40 40 40 5 15 20 60 33 2 59 Phonak Ambra, CIC 1.33 P3 m 5 5 30 45 10 45 50 75 33 3 82 Bernafon CN7 air, RIC 1.11 P4 f 5 25 45 55 20 25 35 55 33 -2 72 Phonak Audeo, RIC 1.41 P5 f 25 30 35 45 25 30 40 45 34 -2 37 Starkey Zon 7, RIC 1.16

P6 m 20 40 40 50 20 30 40 50 36 3 65 Unitron Moxi Kiss, RIC 1.44 P7 f 15 15 45 50 20 25 60 60 36 -2 64 Phonak Audeo, RIC 1.72 P8 f 25 25 50 45 25 30 50 50 38 4 69 Widex Clear, RIC 1.27 P9 f 30 40 40 50 25 45 40 50 40 0 71 Oticon ActoPro, RIC 1.35 P10 m 35 40 40 70 35 40 30 55 43 -1 69 Resound dot2, RIC 1.46 P11 m 40 45 40 50 35 40 50 65 46 -3 67 Oticon ACPI, ITC 1.42 P12 f 40 30 50 55 45 40 50 55 46 -1 86 Phonak Cassia, ITE 1.30 P13 f 30 45 45 65 35 45 50 55 46 3 74 Phonak Audeo, CIC 1.62 P14 m 15 40 50 75 15 30 55 90 46 -3 73 Oticon YGPR, CIC 1.11 P15 m 35 45 40 60 40 45 45 70 48 1 87 Phonak Versata, ITE 1.66 P16 m 50 45 40 55 55 45 45 55 49 -3 73 Siemens Life 700, BTE 1.37 P17 f 40 45 50 70 50 45 45 50 49 0 65 Siemens M50, ITE 1.94 P18 m 20 40 50 60 30 60 70 70 50 -3 67 Oticon ACPI, CIC 2.83 P19 m 30 25 65 70 20 25 80 85 50 -2 73 Phonak Ambra, BTE 2.03 P20 m 45 50 60 50 50 60 50 50 52 -3 70 Phonak Audeo, RIC 2.02 P21 f 40 50 55 60 55 55 55 60 54 2 80 Phonak Audeo, RIC 2.63 P22 m 45 50 60 60 45 50 60 60 54 4 73 Phonak Audeo, RIC 2.35 P23 m 25 50 50 100 25 50 55 85 55 0 79 Phonak Audeo, RIC 1.16 P24 m 20 55 75 80 35 50 65 70 56 -1 87 Phonak Certena, ITC 1.97 P25 m 55 65 85 80 50 65 75 85 70 -3 72 Siemens Cielo, BTE 2.17

3.2.2 AMP test The Adaptive Music Perception (AMP) test was used to assess the effect of hearing aids on music perception in HI listeners. The AMP test is fully described in Kirchberger & Russo (2015) but a brief description follows: The AMP is a computer-driven music test battery that features four subtests to investigate the perception of the musical dimensions meter, harmony, melody, and timbre. These four mid-level dimensions are constructed from 10 low-level dimensions D1 to D10 such as level or duration. In each of the subtests, listeners are asked to make a response with respect to a mid-level dimension (e.g., meter) while adaptively manipulating an underlying low-level dimensions (e.g., level). After the adaptation process is finished, a discrimination threshold for each low-level dimension is determined.

For the study, we used the meter, harmony, and timbre subtest and omitted the melody subtest as it was very challenging for musically inexperienced participants (Kirchberger & Russo 2015). In the

73 Chapter 3: Music Perception: Aided vs. Unaided meter test, a sequence of six beats was played back isochronously and participants were asked to judge the meter of the sequence. The strong and weak beats differed in one of the low-level dimensions level (D1), pitch (D2), or duration (D3). In the harmony test, two chord progression were played back and participants were asked to decide which progression ended less resolved. The chord progressions differed in the last chord and either in acoustic dissonance (D4) or intonation (D5). In the timbre test, three tones were played back in succession and participants had to identify which tone sounded different. The respective tone differed in one of the timbral dimensions brightness (D8), attack (D9), or spectral irregularity (D10).

3.2.3 Procedure Participants were invited to three sessions: one screening and two test sessions. In the screening session, the participants’ audiometric data was assessed if the previous measurement dated back more than a year from the test date. In-situ measurements were carried out to check that the hearing aids were functional and did not apply frequency lowering. In-situ measurements in audiometry refer to measurements that are conducted in the ear with the hearing aid and coupling set in place (Pederson 2012). In this study, in-situ measurements were conducted to control for the participants’ hearing-aid performance. Probe tubes were inserted into the left and right ear canal while the participants listened with their hearing aids to a set of stimuli from the AMP test. For the in-situ measurements and also for the testing in the other two sessions, the participants’ hearing aids were set to the program with which they normally listened to music. Finally, the individual playback level (40 dB sensation level) for the test sessions was determined according to the procedure in Kirch- berger and Russo (2015).

In the second and third session, participants carried out the AMP test once unaided and once aided. To compensate for a potential session effect as measured in Kirchberger and Russo (2015), the order of the conditions (unaided, aided) was counterbalanced across sessions: half (N=12) of the participants started without hearing aids while the other half (N=13) started with hearing aids. Alloca- tion of participants to the two groups was controlled in a manner that minimized differences in hearing loss, music experience, or age.

74 Chapter 3: Music Perception: Aided vs. Unaided

3.3 Results All 25 participants completed the meter and the timbre test of the AMP test battery. Twenty participants carried out the harmony test. The data collection of five participants in the harmony test was inhibited due to scheduling conflicts.

On each dimension D1-D5 and D8-D10, an analysis of variance (ANOVA) was performed to compare aided and unaided performance. The participants’ mean discrimination thresholds and the ANOVA test statistics are displayed in Table 3:2. The discrimination thresholds were higher in the aided condition for 6 out of 8 dimensions (D1, D2, D3, D4, D9, and D10). Differences between conditions were marginally significant for D1: level (p=0.059) and D9: attack (p=0.063).

Table 3:2 Mean discrimination thresholds in the unaided and aided condition and the ANOVA statistics for the dimensions of the meter, harmony, and timbre subtests of the AMP test.

mean discrimination ANOVA threshold

subtest dimension unaided aided F P

D1 (dB) 1.95 2.44 , = 3.94 0.059

meter D2 (Hz) 2.89 2.94 , = 0.05 0.826

D3 (ms) 55.3 55.5 , < 0.01 0.973 D4 (Hz) 0.213 0.245 = 0.55 0.468 harmony , D5 (Hz) 4.64 3.65 , = 1.95 0.178

D8 (dB) 0.417 0.415 , < 0.01 0.972

timbre D9 (ms) 213 275 , = 3.79 0.063

D10 (dB) 5.33 6.01 , = 2.00 0.170

As level and attack relate to the perception of dynamics, a post-hoc analysis was performed to assess whether the impairment is a side-effect of dynamic compression in hearing aids. Dynamic compression was assessed based on the recordings from the in-situ measurements. The stimuli set included the reference tone from the meter and timbre test which was played back at the original level and at a level which was increased by 6 . The corresponding in-situ levels of both playback levels were used to establish the compression ratio CR, a measure for the strength of the hearing- aid compression. CR was calculated as the ratio of the original level increase (6 dB) and the level increase which was measured in-situ (Equation 3:1; c.f. Figure 1:3).

6 = ∆

Equation 3:1 – Calculation of the compression ratio CR.

75 Chapter 3: Music Perception: Aided vs. Unaided

The measurements were averaged across ears to retrieve one CR value per participant (see Table 3:1). The compression ratio CR was correlated with the differences between thresholds in the aided and unaided condition. The Pearson correlation was not significant for D1: level ( = 0.139 , = 0.508 ) and significant for D9: attack ( = 0.448 , = 0.025 ).

3.4 Discussion The marginally significant threshold elevations of D1 (level) and D9 (attack) in the aided condition indicate that hearing aids may impair rather than improve the perception of music, specifically with regard to the perception of meter and timbre. The significant correlation of the compression ratio CR with the difference in aided and unaided thresholds for D9 (attack) lends further support to the notion that dynamic compression in hearing aids was responsible for differences across aided and unaided conditions. Hearing aids apply dynamic compression on the acoustic input to ensure audibility for soft signals without over-amplifying loud signals (Kates 2010). Compression flattens the slope of the attack so that higher thresholds are needed to detect differences. Attack is important for the identification of musical instruments (Iverson & Krumhansl 1993). It is often the most salient predictor of timbre differences (Ilmoniemi, Valimaki, & Huotilainen 2004) and crucial to distinguish continuant instruments that are blown or bowed from impulsive instruments that are struck or plucked (McAdams 2013). Clark et al. (1963) showed that removing the attack from instrumental tones impaired the recognition more than removing steady states and decays. In another experiment, Saldanha and Corso (1964) also showed that the identification accuracy is impaired when the attacks are deleted from the instrumental recordings.

It is therefore important that hearing aids preserve the perception of attack to avoid damage to the perception of timbre in music.

3.5 Conclusion Hearing aids can have detrimental effects on music perception. Dynamic compression in hearing aids significantly impairs the perception of attack, which is an important dimension of timbre. Fur- thermore, hearing aids may affect the perception of meter. The necessary level differences to distinguish strong and weak beats were near-significantly higher when participants listened with their hearing aids. The experimental findings therefore support the notion to reduce the amount of compression in hearing aids when listening to music.

76 Chapter 3: Music Perception: Aided vs. Unaided

Acknowledgments

The research protocol for this study was approved by the Ethics Commission of the ETH Zürich (EK 2013-N-33) and the Ryerson University Research Ethics Board (2013-128-1).

This research was supported by Phonak AG and an NSERC Discovery grant awarded to the second author.

The authors declare no other conflict of interest.

77 Chapter 3: Music Perception: Aided vs. Unaided

References

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Brennan, M, A., McCreery, R., Kopun, J., Hoover, B., Alexander, J., Lewis, D., & Stelmachowicz, P. G. (2014). Paired Comparisons of Nonlinear Frequency Compression, Extended Bandwidth, and Re- stricted Bandwidth Hearing Aid Processing for Children and Adults with Hearing Loss. Journal of the American Academy of Audiology, 25(10), 983-998.

Clark Jr, M., Luce, D., Abrams, R., Schlossberg, H., & Rome, J. (1963). Preliminary experiments on the aural significance of parts of tones of orchestral instruments and on choral tones. Journal of the Audio Engineering Society , 11 (1), 45-54.

Croghan, N. B., Arehart, K. H., & Kates, J. M. (2014). Music preferences with hearing aids: Effects of signal properties, compression settings, and listener characteristics. Ear and Hearing, 35(5), e170– e184.

Davies-Venn, E., Souza, P., & Fabry, D. (2007). Speech and music quality ratings for linear and nonlinear hearing aid circuitry. Journal of the American Academy of Audiology, 18(8), 688-699.

Feldmann, H. & Kumpf, W. (1988). Listening to music in the hard-of-hearing individual with and without hearing aid. Laryngologie, Rhinologie, Otologie, 67(10), 489-497.

Hansen, M. (2002). Effects of multi-channel compression time constants on subjectively perceive sound quality and speech intelligibility. Ear and Hearing, 45(3), 369-380.

Higgins, P., Searchfield, G., & Coad, G. (2012). A comparison between the first-fit settings of two multichannel digital signal-processing strategies: Music quality ratings and speech-in-noise scores. American Journal of Audiology, 21(1), 13-21.

Ilmoniemi, M., Valimaki, V., & Huotilainen, M. (2004, June). Subjective evaluation of musical instrument timbre modifications. In Joint Baltic-Nordic Acoustic Meeting (pp. 8-10).

Iverson, P., & Krumhansl, C. L. (1993). Isolating the dynamic attributes of musical timbrea). The Journal of the Acoustical Society of America , 94 (5), 2595-2603.

Kates, J. M. (2010). Understanding compression: Modeling the effects of dynamic-range compression in hearing aids. International Journal of Audiology, 49(6), 395–409.

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Kirchberger, M. J., & Russo, F. A. (2015). Development of the Adaptive Music Perception Test. Ear and Hearing, 36(2), 217-228.

Larkin W. D. (1983). Pitch vulnerability in sensorineural hearing impairment. International Journal of Audiology, 22(5), 480-493.

Leek, M. R., Molis, M. R., Kubli, L. R., & Tufts, J. B. (2008). Enjoyment of music by elderly hearing- impaired listeners. Journal of the American Academy of Audiology, 19(6), 519-526.

Leek, M. R. & Summers V. (2001) Pitch strength and pitch dominance of iterated rippled noises in hearing-impaired listeners. The Journal of the Acoustical Society of America 109(6), 2944–2954.

Madsen, S. M. & Moore, B. C. J. (2014). Music and Hearing Aids. Trends in Hearing, 18, DOI:10.1177/2331216514558271

McAdams, S. (2013). Musical Timbre Perception. In Psychology of Music (pp. 35-67), Elsevier.

Neukomm, E. (2006). Musikhören bei Schwerhörigkeit mit und ohne Hörgerät [Listening to music with hearing loss, unaided and aided]. Retrieved from: http://www.pro- audito.ch/fileadmin/daten/Neukommpas_musikstudie.pdf

Parsa, V., Scollie, S., Glista, D., & Seelisch, A. (2013). Nonlinear frequency compression: effects on sound quality ratings of speech and music. Trends in Amplification, 17(1), 54-68.

Pedersen, J. N. (2012). The Inside Scoop on In-situ Testing. Audiology Online . Retrieved from http://www.audiologyonline.com/articles/inside-scoop-on-in-situ-771

Saldanha, E. L., & Corso, J. F. (1964). Timbre cues and the identification of musical instruments. The Journal of the Acoustical Society of America , 36 (11), 2021-2026.

Tufts, J. B., Molis M. R., & Leek M. R. (2005). Perception of dissonance by people with normal hearing and sensorineural hearing loss. The Journal of the Acoustical Society of America 118(2), 955– 967.

Uys, M., Pottas, L., Vinck, B., & van Dijk, C. (2012). The influence of non-linear frequency compression on the perception of music by adults with a moderate to severe hearing loss: Subjective impressions. South African Journal of Communication Disorders, 59, 53-67. van Buuren, R. A., Festen, J. M., & Houtgast, T. (1999). Compression and expansion of the temporal envelope: Evaluation of speech intelligibility and sound quality. The Journal of the Acoustical Society of America , 105 (5), 2903-2913.

80 Chapter 4: Dynamics of Music and Perception of Dynamic Compression

Chapter 4 Dynamic Range across Music Genres and the Perception of Dynamic Compression in Hearing-Impaired Listeners

The content in this chapter was published in the journal Trends in Hearing (February 2016).

Impact Factor: 1.92

Authors: Martin Kirchberger and Frank Russo

Kirchberger, M., & Russo, F. A. (2016). Dynamic Range Across Music Genres and the Perception of Dynamic Compression in Hearing-Impaired Listeners. Trends in Hearing , 20 , DOI: 10.1177/2331216516630549.

81 Chapter 4: Dynamics of Music and Perception of Dynamic Compression

Abstract

Dynamic range compression serves different purposes in the music and hearing-aid industries. In the music industry, it is used to make music louder and more attractive to normal-hearing listeners. In the hearing-aid industry, it is used to map the variable dynamic range of acoustic signals to the reduced dynamic range of hearing-impaired listeners. Hence, hearing-aided listeners will typically re- ceive a dual dose of compression when listening to recorded music.

The present study involved an acoustic analysis of dynamic range across a cross-section of recorded music as well as a perceptual study comparing the efficacy of different compression schemes. The acoustic analysis revealed that the dynamic range of samples from popular genres, such as rock or rap, was generally smaller than the dynamic range of samples from classical genres, such as opera and orchestra. By comparison, the dynamic range of speech, based on recordings of monologues in quiet, was larger than the dynamic range of all music genres tested. The perceptual study compared the effect of the prescription rule NAL-NL2 with a semi-compressive and a linear scheme. Music subjected to linear processing was rated higher in dynamics and quality, followed by the semi- compressive and the NAL-NL2 setting. These findings advise against NAL-NL2 as a prescription rule for recorded music and recommend linear settings.

4.1 Introduction

4.1.1 Compression in music production Dynamic range refers to the level difference between the highest and lowest-level passages of an audio signal. Dynamic range compression (or dynamic compression) is a method to reduce the dynamic range by amplifying passages that are low in intensity more than passages that are high in intensity. Dynamic compression can serve different purposes in the music production process. It may have an aesthetic purpose in the mastering process to make the mix more coherent and to minimize excessive loudness changes within a song (Katz & Katz 2003). It may also have a pragmatic purpose if it is employed to adapt the dynamic range of music to the technical limitations of recording or playback devices. Dynamic compression, however, can and has infamously been used to increase the

82 Chapter 4: Dynamics of Music and Perception of Dynamic Compression loudness of a song. It is widely believed in the music industry that loudness levels and record sales are correlated (Vickers 2011). A very strong compressor called a limiter is employed to reduce peak levels. A so-called makeup gain then amplifies the whole signal until the peaks reach full scale again. This method increases the overall energy of the signal but often introduces distortion (Kates 2010) and compromises signal quality. Even when distortion is not perceptible, highly compressed music can become physically or mentally tiring over time (Vickers 2011).

4.1.2 Compression in hearing aids Hearing aids incorporate dynamic range compression to compensate for higher absolute hearing thresholds and the effects of loudness recruitment, which are commonly experienced by people with sensorineural hearing loss. Loudness recruitment is an abnormally rapid growth in loudness that ac- companies increases in supra-threshold stimulus intensity (Villchur 1974). A hearing aid must amplify soft passages more than loud passages so as to increase audibility while maintaining a comfortable listening experience. Fortunately, hearing aids provide some flexibility in the extent to which compression is applied. Important compression parameters are attack time, release time, compression ratio, compression threshold, and number of channels (Giannoulis, Massberg, & Reiss 2012). The parameterizations vary across hearing-aid manufacturers (Moore, Füllgrabe, & Stone 2011) and may also depend on the detected signal class such, as speech or music.

There are established prescription rules that define gain targets for speech as a function of frequency, sound level, and hearing loss. The actual gains that are achieved for dynamic signals can deviate from the gain targets depending on the choice of time constants.

CAMEQ (Moore 2005; Moore, Glasberg, & Stone 1999) and its successor CAM2 (Moore, Glasberg, & Stone 2010) are fitting recommendations from the University of Cambridge. The later version CAM2 uses a revised loudness model for the gain calculations (Moore & Glasberg 2004). Furthermore, the gain recommendations were extended from frequencies up to 6 in CAMEQ to frequencies up to 10 in CAM2. In general, the gains between 1 and 4 are between 1 and 3 lower in CAM2 than in CAMEQ (Moore & Sek 2013).

Another established fitting method is DSL - Desired Sensation Level - from the National Centre for Audiology at Western University, Canada (Scollie et al. 2005). The DSL prescriptions were originally

83 Chapter 4: Dynamics of Music and Perception of Dynamic Compression developed to address the specific amplification needs of children (Seewald, Ross, & Spiro 1985). A later version of DSL, DSL v5 Adult, supports hearing instrument fitting for adults (Scollie et al. 2005; Jenstad et al. 2007).

The National Acoustic Laboratories in Australia provide the prescription rule NAL-NL1 (Dillon 1999) and its successor NAL-NL2 (Dillon et al. 2011; Keidser et al. 2011). NAL-NL1 is based on the assump- tion, that speech is fully understood when all speech components are audible. NAL-NL2 accounts for the fact that as the hearing loss gets more severe, less information is extracted even when it is audible above threshold (Keidser et al. 2011).NAL-NL2 recommends gains for frequencies up to 8 , whereas NAL-NL1 is limited to 6 (Moore & Sek 2013). NAL-NL2 prescribes more low- and high- frequency gain and less mid-frequency gain than NAL-NL1 (Johnson & Dillon 2011). In addition, the gender and hearing-aid experience of the patient can be taken into account for the gain pre- calculation with NAL-NL2.

Johnson and Dillon (2011) compared the latest prescription rules CAM2, NAL-NL2, and DSL v5 Adult with regard to insertion gain, loudness, and compression ratio. For speech at a level of 65 , DSL v5 Adult provides most gain in the high frequencies. Regarding overall loudness, CAM2 is louder than DSL and NAL-NL2. With regard to the compression ratios, CAM2 and NAL-NL2 provide generally more compression than DSL v5 Adult. For sloping hearing loss, however, the compression ratio of DSL v5 Adult is higher than the compression ratio of NAL-NL2.

These prescription rules were primarily designed for speech and have not been adapted for music. If the dynamic range of music is different than the dynamic range of speech, then the established prescription rules may be inappropriate for music. Further, different genres of music might be best han- dled using their own prescription rules.

There are several studies that have explored optimal compression schemes for music perception in hearing-impaired listeners (see Table 4:1 for examples of these). In general, the linear or least compressive settings received the best preference or quality ratings. This outcome can be interpreted in the following manner. Hearing-impaired listeners may tolerate not hearing soft passages in favor of rejecting distortions or a reduction in dynamic range caused by dynamic compression. This might be partly due to different priorities when we listen to music or speech. It has been argued that the primary focus in music listening is enjoyment rather than intelligibility (Chasin & Russo 2004). If a passage in music is rendered inaudible, it likely affects the enjoyment of that passage alone. By contrast,

84 Chapter 4: Dynamics of Music and Perception of Dynamic Compression not hearing parts of speech affects the inaudible passages as well as the ability to follow the entire conversation. It therefore seems probable that the optimal trade-off in music between audibility and quality is shifted towards quality so that less compression is more appropriate for music than for speech. Nevertheless, the size of the audio corpora used in the studies listed in Table 4:1 was consistently small and it is thus difficult to generalize the results given the broad diversity of music that exists in the real world. For these reasons, we chose to undertake a formal study of dynamic range across a broad range of recorded music 1.

4.1.3 Dynamic range of music Dynamic properties of recorded music may vary with genre due to differences in various practices including instrumentation and mastering. Previous surveys of dynamic range have focused on differences in dynamic range across eras rather than across genres (Vickers 2010, 2011; Ortner 2012; Deruty & Tardieu 2014). Insights regarding variability in dynamic range across genres may inform the optimization of compression schemes for music.

4.2 Experiment I: Dynamic Range of Music across Genres

4.2.1 Stimuli The music corpus used for analysis contained 100 songs in each of ten genres: chamber music, choir, opera, orchestra, piano music, jazz, pop, rap, rock, and schlager 2. Song selection for the corpus was constrained to release dates between 2000 and 2014 in order to minimize the impact of the historic rise in compression standards that occurred prior to this era (Deruty & Tardieu 2014; Ortner 2012). All songs were commercially available and were retrieved in CD quality with 44.1-kHz sampling rate and 16-bit resolution. The songs were chosen from a wide range of composers and labels to avoid a

1 We chose to focus our investigation on recorded music exclusively. Live music tends to have a larger dynamic range than the recorded and mastered reproduction, however, nowadays the consumption of live music is far less common than the consumption of recorded music. A Canadian study with a sample of 1232 participants (Crofford 2007) yielded an average of 10.5 live concert attendances per year. Assuming an average of 3 hours per concert, the accumulated amount of live music consumed within a year would be less than 40 hours. Total music consumption, however, has been estimated at 2.5 hours per day (Bersch-Burauel 2004), adding up to over 900 hours per year. In this comparison, live music consumption would account for less than 4% of total music consumption. 2 Also known as German entertainer music.

85 Chapter 4: Dynamics of Music and Perception of Dynamic Compression

Table 4:1 Peer-reviewed research exploring the effect of different compression settings on music perception in hearing- impaired listeners (CR: compression ratio, AT: attack time, RT: release time, CT: compression thresholds, WDRC: wide dynamic range compression (multiband dynamic compression), ADRO: adaptive dynamic range compression, HA = hearing aid.

# of stimuli / Reference genres Methods / Conditions Results

Playback to one ear only. Condi- van Buuren, tions include all combinations of Festen, & 4 / piano, orches- four different CRs (0.25, 0.5, 2, 4) Highest pleasantness ratings for Houtgast tra, pop, lied and 3 different number of bands linear amplification (1999) from (1,4,16) plus an uncom- pressed condition as benchmark.

Experiment 1: Conditions included 4 AT/RT combinations: 1/40 10/400 4 / orchestra, 1/4000 100/4000. Gain shape was chamber music, defined by NAL-R rule. CR was pop (not specified Highest preference for longer Hansen (2002) fixed at 2.1 :1 for all channels and which genre RT, smaller CR and lower CT. subjects. Experiment 2: Conditions contributed 2 were 4 combinations of AT/ stimuli) RT/CT/CR: 1/40/20/2.1, 1/40/50/3, 1/40/50/2.1, 1/4000/20/2.1

Davies-Venn, Comparison of peak clipping, com- 2 / classic instru- WDRC preferred over peak Souza, & Fabry pression limiting, and WDRC for mental, lied clipping and limiting. (2007) 80dBSPL (loud) signals.

Lower CR and longer RT were Arehart, Kates, 3 / orchestra, jazz WDRC with 18 bands in 4 combina- preferred. All compressive set- & Anderson instrumental, tions of CR/RT: 10/10ms, 10/70ms, tings were rated worse than the (2011) single voice 2/70ms, 2/200ms uncompressive setting (linear gain shape NAL-R).

ADRO preferred to WDRC. However, the experimental set- Higgins, Comparison of ADRO and WDRC. 3 / classic, jazz, up does not allow to attribute Searchfield, & ADRO was less compressive than rock preference only to the linearity Coad (2012) WDRC. but also to further differences such as gain shape.

Comparison of slow (AT: 50ms, RT: Longer time constants were Moore, Füll- 3s) and fast compression speeds preferred for classic at 65dB grabe, & Stone 2 / jazz, classic (AT: 10ms, RT: 100ms) at 3 input SPL and 80dB SPL and for jazz (2011) levels (dB SPL): 50, 65, and 80. at 80 dB SPL.

WDRC generally least preferred. For classic, linear processing 3 levels of music industry compres- and slow WDRC was equally sion (no; mild, CT: -8 dBFS; heavy: Croghan, Are- preferred. For rock, linear was -20 dBFS) combined with 3 levels hart, & Kates 2 / classic, rock preferred over slow WDRC. The of HA compression (linear; fast, RT: (2014) effect of HA WDRC was more 50ms; slow RT: 1000ms) with either important than music-industry 3 or 18 channels. compression limiting for music preference.

86 Chapter 4: Dynamics of Music and Perception of Dynamic Compression bias from a single composer or mastering engineer. For the dynamic range analysis, a 45-s segment was excerpted from the center of each song, converted to mono and normalized in RMS level. The taxonomy of genre is not standardized but music retailers are an influential source of genre classification (Pachet & Cazaly 2000). The biggest internet retailer of music is iTunes with a database of more than 30 million songs (Neumayr & Joyce 2015). Although iTunes provides a convenient classification, it classifies albums rather than individual songs (Palmason 2011). We therefore chose to use iTunes as a first classifier and added further classification criteria based on the properties described in Table 4:2.

Table 4:2 Additional criteria for each genre that the songs and stimuli (45-s segments) had to meet beyond the iTunes genre classification.

Genre Additional criteria For comparative purposes, speech stimu- Chamber Instrumentation: string quartets. li of one female and one male native

Stimulus contains only vocal elements and speaker of 14 different languages includ- Choir no accompanying instruments. ing Chinese, English, Spanish, French, Stimulus contains vocal and instrumental Opera elements. Japanese, German, Italian, Portuguese,

Orchestra Only non-vocal excerpts accepted. Hungarian, Bulgarian, Polish, Dutch, Slo-

Piano Only solo piano accepted. venian, and Danish were added to the audio corpus. All monologues are trans- Stimulus contains drums, bass, piano, and Jazz a lead brass instrument. lations of the same original German text.

Stimulus contains vocal and instrumental The monologues were recorded in pro- Pop elements. fessional studios in noise-free environ-

Stimulus contains rapped vocal elements ments with a 1-m distance between the Rap and instrumental elements. speaker and microphone. The recordings

Stimulus contains vocals and a distorted were provided by Phonak and are availa- Rock guitar. ble in the Phonak iPFG fitting software. Schlager Stimulus contains vocals.

4.2.2 Analysis There are several definitions for measuring the dynamic range of music (Boley, Danner, & Lester 2010). The EBU-Tech 3342 (2011) recommendation from the European Broadcasting Union defines loudness range as the difference between the 95 th and 10 th percentiles measured with overlapping

87 Chapter 4: Dynamics of Music and Perception of Dynamic Compression windows of 3 duration. Another common measure, the crest factor, is defined as the sound level difference between some estimation of peak level and some estimation of central tendency (e.g., average). The exact determination of the peak or time-averaged level, however, varies among studies (Ortner 2012; Croghan, Arehart & Kates 2014; Deruty & Tardieu 2014). The IEC 60118-15 (2008) recommendation was developed to characterize signal processing in hearing aids. It uses a standardized test signal which is composed of short speech segments from female Arabic, English, French, German, Mandarin, and Spanish speakers as hearing-aid input signal to analyze the signal processing. The processed signal is partitioned into third-octave bands and the dynamic range analysis is conducted for each frequency band individually. The analyzing window is set at 125 with 50% overlap. The signal duration for analysis specified in the standard is 45 . The dynamic range is usually reported for the 30 th , 65 th , and 99 th percentiles. The IEC standard was used as the method of analysis in this experiment. It is the most appropriate method for dynamic range analysis in the context of hearing-aid signal processing as it uses window lengths that correspond with the time resolution of loudness perception (Chalupper 2002; Moore 2014) and provides a frequency-dependent analysis. It is therefore possible to analyze the dynamic range of any kind of acoustic signal including music. All stimuli were RMS equalized prior to analysis in order to allow for averaging across segments within genres.

4.2.3 Results The results of the dynamic range analysis for each genre (100 samples) and speech (28 samples) are depicted in Figure 4:1. The percentiles are reported in SPL and shown across frequency in . The percentiles of the modern genres (pop, rap, rock, and schlager) cluster together more than the percentiles of the classical genres (chamber, choir, opera, orchestra, piano), with the extent of clus- tering in jazz falling somewhere in between. Within the classical genres, opera and choir show higher differences between the highest and lowest percentiles than chamber, orchestra, and piano, especially in the frequency region between 0.5 and 2 .

Figure 4:2 shows a dynamic range comparison of all genres calculated as the difference between the 99 th and 30 th percentile. According to this analysis, speech is generally highest in dynamic range in all frequency bands followed by the classical genres, jazz, and the modern genres.

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Speech is only locally surpassed by chamber music in the lowest two frequency bands ([ 110 to 140 ]; [ 140 to 177 ]) and by orchestra and opera in the lowest band.

Speech 80 60 40

dB SPL dB 20 0 0.2 0.5 1 2 5 10 kHz Chamber Jazz 80 80 60 60 40 40 dB SPL dB dB SPL dB 20 20 0 0 0.2 0.5 1 2 5 10 kHz 0.2 0.5 1 2 5 10 kHz Choir Pop 80 80 60 60 40 40 dB SPL dB 20 SPL dB 20 0 0 0.2 0.5 1 2 5 10 kHz 0.2 0.5 1 2 5 10 kHz Opera Rap 80 80 60 60 40 40 dB SPL dB dB SPL dB 20 20 0 0 0.2 0.5 1 2 5 10 kHz 0.2 0.5 1 2 5 10 kHz Orchestra Rock 80 80 60 60 40 40 dB SPL dB 20 SPL dB 20 0 0 0.2 0.5 1 2 5 10 kHz 0.2 0.5 1 2 5 10 kHz Piano Schlager 80 80 60 60 40 40 dB SPL dB 20 SPL dB 20 0 0 0.2 0.5 1 2 5 10 kHz 0.2 0.5 1 2 5 10 kHz

Figure 4:1 Dynamic ranges of speech and 10 different music genres. The lines represent th th percentiles in dB (SPL) across frequency in kHz (99 : upper dashed line, 90 : upper solid line, 65 th : thick line, 30 th : lower solid line, and 10 th : lower dashed line).

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The findings indicate that the dynamic range of music is generally smaller than the dynamic range of speech in quiet. The differences in dynamic range across genres can be attributed to acoustic properties such as instrumentation and to genre-dependent compression preferences. A further investigation to reveal the extent to which acoustic properties or compression preferences contribute to overall differences in dynamic range, however, is beyond the scope of this chapter.

40 ∆dB Chamber SPL Choir Opera Orchestra Piano 35 Jazz Pop Rap Rock Schlager 30 Speech

5 0.2 0.5 1 2 5 10 kHz

Figure 4:2 Dynamic range comparison between different music genres and across frequency. The dynamic range are calculated as the difference between the 99 th and 30 th percentiles according to the IEC 60118-15 standard.

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4.2.4 Conclusion The dynamic range of recorded music across genres based on an audio corpus of 1000 songs was found to be smaller than the dynamic range of monologue speech in quiet. Samples from modern genres such as pop, rap, rock, and schlager generally had the smallest dynamic range, followed by samples from jazz and classical genres such as chamber, choir, orchestra, piano, and opera. Only in the lower frequencies was the dynamic range of speech surpassed by the dynamic range of music, and then only in the case of chamber music, opera, and orchestra.

4.3 Experiment II: Effect of Compression Ratio on Music Perception

4.3.1 Rationale Dynamic compression reduces the dynamic range of a stimulus to provide audibility for low-level passages without reaching uncomfortable loudness levels for high-level signals. Signals with a small dynamic range need less compression than signals with a large dynamic range to ensure audibility and comfortable listening levels. Based on the analysis, the dynamic range of music and particularly the dynamic range of music from modern genres, is smaller than that found in monologue speech in quiet. We therefore hypothesize that less compression is preferable for music relative to speech, especially for music from modern genres 3.

To test our hypotheses, we carried out a study and assessed the sound quality of music stimuli from a set of genres in three different conditions: no compression (linear), full compression (NAL-NL2), and semi-compression (half the compression ratio of NAL-NL2). Apart from the compression ratio, all other compression parameters remained equivalent across conditions. In order to keep the session time for the participants below two hours, we tested only half of the genres from Experiment I: choir, opera, orchestra, pop, and schlager. We predicted that the linear condition would provide the best sound quality for the stimuli from the modern genres (pop and schlager) and that the semi- compressive condition would provide the best quality for the stimuli from the classical genres (choir,

3 Chamber music, opera, and orchestra surpass the dynamic range of speech in the lower frequencies, however, these frequency components are less relevant in the context of dynamic compression with hearing aids. Hearing loss is generally less predominant in the lower frequencies (Bisgaard, Vlaming, & Dahlquist 2010) and low-frequency gains are constricted by potential feedback from leakage or vents (Cox 1982) and physical limits of the speaker. As a consequence, the hypothesis refers to frequencies above 200 Hz for which the dynamic range of speech is higher than the dynamic range of all analyzed music genres (Figure 4:2).

91 Chapter 4: Dynamics of Music and Perception of Dynamic Compression opera, and orchestra). In addition to sound quality, participants were asked to provide direct judgments of dynamics. Dynamics was defined as the perceptual correlate to dynamic range. The dynamics ratings were used to verify whether the differences in dynamic range across the three dynamic compression schemes were perceptible. Potential differences between conditions in spectral shape and loudness were controlled and participants were additionally asked to provide direct judgments of loudness.

4.3.2 Participants Thirty-one hearing-impaired listeners (ages 48 -80, mean age 69) were recruited from the internal database of Sonova AG headquarters, Stäfa, Switzerland. The audiometric data were assessed within three months of the first test date. All participants were Swiss and native German speakers. The participants’ music experience was assessed with a questionnaire according to Kirchberger and Russo (2015). The questionnaire asks participants a series of questions about music training and activity to arrive at an overall measure of music experience.

All participants were fitted with Phonak Audéo V50 RIC hearing aids according to the NAL-NL2 prescription rule. If the participants did not accept the first fit, changes were made until full acceptance was achieved. The changes affected the overall gain or gain shape, but not the compression strength of the setting. For the coupling, standard domes (open, closed, and power) and receivers (standard, power) were used. The choice of the individual dome was based on the recommendation from the Phonak Target TM fitting software but was subject to change according to the participant’s preference. Participants had worn the hearing aids for at least five weeks and two months on average before the test sessions began. All information regarding the participants is provided in Table 4:3.

Table 4:3 Characteristics of the test participants: audiometric data (dB HL), age (yrs), hearing-aid experience / HAE (yrs), music experience / ME (range from -3: low to 4: high), and coupling (dome and receiver). Note: NT indicates a hearing threshold that was not tested.

Left ear, frequency (kHz) Right ear, frequency (kHz)

0.125 0.25 0.5 1 2 4 6 8 0.125 0.25 0.5 1 2 4 6 8 P1 30 30 35 60 60 70 115 105 30 35 35 45 60 70 90 80 P2 20 10 5 20 65 75 85 100 25 20 10 5 40 70 90 90 P3 10 10 5 25 45 60 85 100 15 10 15 10 55 90 100 100 P4 5 10 20 55 65 70 80 75 10 10 15 30 75 70 90 80 P5 40 45 45 65 70 80 90 80 35 35 40 50 60 80 80 75 P6 25 40 40 75 75 100 105 105 15 20 30 35 45 65 75 85

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P7 10 20 55 70 75 85 95 90 10 10 20 50 65 95 100 100 P8 15 15 25 50 55 75 100 95 15 15 20 25 70 85 100 105 P9 20 15 5 30 45 90 105 95 10 10 10 45 40 100 100 100 P10 25 30 55 70 75 75 80 85 25 25 35 50 70 70 75 75 P11 15 30 55 75 75 80 85 90 40 45 50 65 75 85 100 85 P12 25 40 65 90 75 75 105 >120 30 40 45 60 90 75 90 >120 P13 20 30 35 35 50 60 70 65 30 30 35 40 40 65 85 80 P14 15 15 10 55 60 65 90 95 15 10 10 15 55 65 80 95 P15 40 50 55 80 85 95 100 NT 20 25 40 40 55 80 NT 85 P16 30 30 65 80 80 85 90 85 25 25 35 40 55 80 90 90 P17 10 5 10 45 65 80 105 85 5 10 10 15 65 80 90 75 P18 35 55 60 65 65 65 80 65 45 50 55 55 60 55 65 65 P19 55 60 55 55 55 55 65 70 35 55 55 55 60 70 70 65 P20 35 60 55 65 60 75 105 >105 15 40 50 50 60 60 60 100 P21 60 70 80 85 75 75 80 80 55 60 60 65 85 75 80 85 P22 20 40 45 60 55 60 65 60 20 25 35 50 55 60 65 65 P23 35 55 55 65 70 75 80 80 40 40 55 50 60 75 75 85 P24 50 60 50 65 60 65 80 75 35 40 35 40 55 50 60 70 P25 35 55 55 65 75 80 90 105 55 60 60 60 70 85 100 105 P26 30 60 70 55 65 70 75 85 30 35 60 70 65 80 85 105 P27 25 45 45 50 70 60 60 55 20 30 40 50 50 65 55 60 P28 15 35 45 70 60 65 70 95 20 20 40 60 75 70 65 85 P29 30 55 60 55 45 45 50 70 30 40 45 55 50 40 50 65 P30 25 45 65 70 60 70 75 85 30 30 45 65 70 70 75 70 P31 40 45 55 50 55 60 65 90 45 45 45 55 60 55 80 80

Coupling Sex Age HAE ME Dome Receiver P1 m 80 11 2.5 closed standard P2 f 64 >10 1 open standard P3 m 72 7 -1.5 open standard P4 m 74 12 -2 closed standard P5 m 67 >10 1.5 power standard P6 m 73 8.5 -1 closed standard P7 m 72 6 -2.5 closed power P8 m 70 0.2 -2 open standard P9 m 70 10 -3 open power P10 m 65 8 0 closed standard P11 m 73 16 -2.5 closed power P12 m 68 50 -3 power power P13 m 69 9 -2.5 power standard P14 m 76 12 0 closed standard P15 m 71 5 0.5 closed power P16 m 75 21 1.5 power power P17 f 55 7 -2 closed standard P18 f 66 25 0 closed standard P19 m 73 10 -2 power standard P20 m 68 30 -2 power power P21 m 66 25 -2 power power P22 m 67 13 2 closed power P23 m 77 30 0.5 power standard P24 f 78 3 -2 power standard P25 m 76 >10 -1.5 power power P26 m 67 37 1 power power P27 m 48 7 -2 closed standard

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P28 m 70 16 1.5 power power P29 f 69 10 -3 power standard P30 m 51 >10 4 cShell standard P31 f 72 28 0.5 power power

4.3.3 Test conditions In the experiment, participants compared the effect of linear, semi-compressive, and compressive parameterizations of hearing aids on the perception of 20 music segments. In the compressive condition, the compression parameters of the participant’s individual NAL-NL2 fitting were used. In the linear and the semi-compressive condition, the compression ratio (CR) of the compressive condition was modified to = 0 and to = 1⁄ 2 ∙ respectively. All other compression parameters remained the same. The hearing aids had 20 compression channels. The time constants were band-dependent and ranged from 10 for attack and 50 for release in the lower frequencies to 6 for attack and 37 for release in the higher frequencies.

CONTROL OF SPECTRAL SHAPE AND LEVEL

Dynamic compression can change the overall level of a signal. Moreover, in multiband dynamic compression systems, such as that which can be found in state-of-the-art hearing aids, the gain calculation and application differs across bands. As a consequence, multiband dynamic compression can change the level of each band independently and therefore also modify the spectral shape of a signal (Chasin & Russo 2004). The experiment, however, aims at investigating the perception of different dynamic ranges. Changes in spectral shape across conditions would impose a bias. To limit this potential bias, controls were put in place so that within each band, the same gain was applied (on average) in the linear, semi-compressive, and compressive setting. Specifically, the gain curves of the three different conditions within each band were aligned to intersect at the RMS level of the input in the corresponding band (Figure 4:3). As the intersection was already defined by the compressive gain curve (NAL-NL2 fitting) and the RMS levels of the stimuli, the linear and semi-compressive gain curves were adjusted so that they intersected at the same point. The RMS levels of the stimuli across bands were measured with the same setup as described later in section 4.3.4. The measurements were retrieved from the hearing aid so that any potential inaccuracies of the transfer functions for the loudspeakers, the head, and the microphones were accounted for. To further increase the preci-

94 Chapter 4: Dynamics of Music and Perception of Dynamic Compression sion, the RMS measurements were conducted for both ears so that two different RMS sets were available for the right and left hearing aid correspondingly.

linear semi-compressive gain (dB) gain compressive Δgain mean rms level Δgain

Δinput

input level (dB)

Figure 4:3: Schematic gain curves within a compression band for the linear, semi-compressive, and compressive condition.

The compression ratio of the semi-compressive condition ( = ∆/∆) is half the compression ratio of the compressive condition ( = 2 ∗ ∆/∆).

The gain curve alignment was carried out manually for both conditions, each band (20), segment (20), participant (31), and both ears resulting in 2 x 20 x 20 x 31 x 2 = 49600 manually adjusted curves.

CONTROL OF LOUDNESS

We further controlled the loudness of all stimuli with the dynamic loudness model (DLM) by Cha- lupper and Fastl (2002). In contrast to other loudness models such as the well-established Cambridge loudness model developed by Moore (2014), DLM supports the loudness calculation of non- stationary signals in hearing-impaired listeners. To simulate each participant’s individual hearing loss, the air-conduction thresholds, bone-conduction thresholds and uncomfortable loudness levels at 0.5, 1, 2, and 4 were entered into the model. As the lengths of the stimuli were between 9 and

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16 , it was necessary to average the loudness values of the model across time. The long-term loudness of the whole stimulus was determined according to Croghan, Arehart, and Kates (2012) as the mean of all long-term loudness levels that were above 2 (corresponding to absolute threshold). If loudness differences between the 3 conditions of a music segment were greater than 1 , the linear or semi-compressed versions were amplified so that the deviations were within 1 of the compressed version. Figure 4:4 illustrates the loudness curves for one segment and participant combination (segment 3, participant 29).

Figure 4:4 Example loudness curves of the linear, semi-compressive, and compressive version. (Here for participant 29 and stimulus 3).

4.3.4 Test stimuli Twenty songs (four from each genre choir, opera, orchestra, pop, and schlager) were used from the audio corpus described in the first experiment. Segments were selected at points consistent with

96 Chapter 4: Dynamics of Music and Perception of Dynamic Compression musical phrasing. The average dynamic range of the segments of each genre was similar to the dynamic range of the larger sample used in Experiment I (Figure 4:5)4. Further details about the segments are provided in Table 4:4.

Choir II Choir I 80 80 60 60 40 40 dB SPL dB dB SPL dB 20 20 0 0 0.2 0.5 1 2 5 10 kHz 0.2 0.5 1 2 5 10 kHz Opera II Opera I 80 80 60 60 40 40 dB SPL dB 20 dBSPL 20 0 0 0.2 0.5 1 2 5 10 kHz 0.2 0.5 1 2 5 10 kHz Orchestra II Orchestra I 80 80 60 60 40 40 dB SPL dB dB SPL dB 20 20 0 0 0.2 0.5 1 2 5 10 kHz 0.2 0.5 1 2 5 10 kHz Pop II Pop I 80 80 60 60 40 40 dB SPL dB 20 SPL dB 20 0 0 0.2 0.5 1 2 5 10 kHz 0.2 0.5 1 2 5 10 kHz Schlager II Schlager I 80 80 60 60 40 40 dB SPL dB 20 SPL dB 20 0 0 0.2 0.5 1 2 5 10 kHz 0.2 0.5 1 2 5 10 kHz

Figure 4:5 Dynamic range of the test sample in Experiment II (left column) and the audio corpus in Experiment I (right column) for the genres choir, opera, orchestra, pop, and schlager. The lines represent percentiles in dB (SPL) across frequency in kHz (99 th : upper dashed line, 90 th : upper solid line, 65 th : thick line, 30 th : lower solid line, and 10 th : lower dashed line).

The test stimuli for each participant were generated by recording the music segments with a KEMAR manikin (model 45BB by G.R.A.S.) which had hearing aids attached to the ears. Music segments were played back in stereo via two loudspeaker pairs in 1.2 distance at an angle of 30° and −30° , as common practice in audio engineering (Dickreiter et al. 2014). Each loudspeaker pair consisted of a

4 To conduct the dynamic range analysis, the IEC standard requires a stimulus length of 45 sec. As the segments were significantly shorter (Table 4:4), the segments were looped. To avoid anomalies at the transitions, the segments were linearly cross-faded with a 50-msec window.

97 Chapter 4: Dynamics of Music and Perception of Dynamic Compression mid-to-high range speaker (Meyer Sound MM-4-XP) and an aligned subwoofer (Meyer Sound MM-

10-XP). The output level of each music segment was normalized to 65 to ensure realistic and comparable listening levels (Croghan, Arehart, & Kates 2012; 2014). The stimuli were prepared for each participant individually. Exact copies of the participant’s hearing aids were fitted to the KEMAR, including the coupling (open, closed, or power dome), receiver (standard or power), and individual fitting. For each of the 60 test stimuli (20 segments x 3 conditions), the corresponding hearing-aid parameterizations were uploaded to the hearing aids prior to recording the individual stimulus. Re- cordings were made in stereo with microphones located in both KEMAR ears at the position of the eardrums. The recordings were equalized before further processing to compensate for the ear resonance of the KEMAR and the frequency response of the Sennheiser HD 600 headphones that were used for playback in the test sessions.

Table 4:4: Details about the 20 music segments from experiment II.

Genre Title Artist Length Release Music (s) (year) taste

Op. 113 No. 5 - Frauenchöre Kanons - Wille, wille, will Brahms 9.9 2003 0.31 Op. 29 - Zwei Motetten - Es ist das Heil uns kommen her Brahms 12.2 2003 0.17 Choir Jube Domine, for soloists & douple chorus in C major Mendelssohn 10.0 2002 0.17 Op. 69 No. 1 - 1 Herr nun lassest du deinen Diener in Frieden fahren Mendelssohn 15.1 2002 0.28 Carmen - Act 1 - Attention! Chut! Attention! Taisons- Nous! Bizet 11.2 2003 0.21 Don Giovanni Act 1 - Udisti? Qualche bella Mozart 10.1 2007 0.41 Opera Boris Godunov - Act 2 - Uf! Tyazheló! Day Dukh Perevedú Mussorgsky 16.0 2002 -0.21 Rosenkavalier Act 3 - Habn euer Gnaden noch weitere Befehle Strauss 16.3 2001 0.14

Symphonie No. 9 in C-major KV 73 - Molto allegro Mozart 10.7 2002 0.52 Symphony No. 1 in E-flat Orchestra major - Molto Allegro Mozart 8.8 2002 0.79 Symphonie No. 8 - Tempo di Menuetto Beethoven 10.0 2002 0.69 Symphonic Poem Op. 16 - Ma Vlast Hakon Jarl Smetana 11.0 2007 0.31 Pop Downtown Gareth Gates 9.2 2002

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0.17

Tears and rain James Blunt 11.3 2004 -0.07

Shape of my heart Backstreet Boys 12.5 2000 0.31

Rock with you Michael Jackson 8.4 2003 0.21

Kleine Schönheitsfehler Sylvia Martens 12.6 2011 0.38

Sternenfänger Leonard 10.9 2011 0.21 Schlager

Tränen der Liebe Peter Rubin 10.3 2011 0.00

Der Mann ist das Problem Udo Jürgens 14.7 2014 0.17

4.3.5 Listening test The participants conducted listening tests on two separate occasions to compare the linear, semi- compressive, and compressive parameterizations. The setup of the music test was a double-blind multi-stimulus test method similar to a MUSHRA setup as described in the recommendation ITU-R. BS.1534-1 (2001). In each trial, participants had to rate 3 stimuli on a scale from 0 to 100. The 3 stimuli differed in dynamic range and were processed by a linear, a semi- compressive, or a compressive (NAL-NL2) hearing-aid setting.

Participants were asked to make judgments along two dimensions: sound quality and dynamics. Dynamics was explained as the difference between loud and soft passages. The scales used for the ratings ranged from “poor” to “good” for sound quality and from “low” to “high” for dynamics. Partici- pants were instructed to focus on the relative differences between the conditions within one trial rather than trying to make

Figure 4:6 Example screen of the main test.

99 Chapter 4: Dynamics of Music and Perception of Dynamic Compression absolute ratings across trials. Participants were assigned to one of two groups and carried out 20 trials per dimension, one trial for each music segment. Group A started with judgments about the sound quality dimension, while Group B started with judgments about the dynamics dimension. Allo- cation of participants to the two groups was controlled in a manner that minimized differences in age, hearing loss, or music experience.

The tests were implemented in Matlab and displayed as a graphical user interface on a touchscreen in front of the participants. The stimuli were randomly assigned to one of the three channels A, B, or C (c.f. Figure 4:6). The stimuli were looped endlessly and the transitions from the end to the beginning of each loop were not noticeable as the music segments were selected to preserve musical phrasing.

Participants were freely able to switch between channels (stimuli) at any given time. A 5 cross- fade was applied while channel switching in order to avoid switching artifacts such as pops.

Although loudness was well controlled in the experiment, we additionally asked participants to compare the loudness of the test stimuli across conditions. In 20 trials, participants had to compare and rate the loudness of the linear, semi-compressive, and compressive version of a music segment on a scale from 0 to 100. Scale ends were labeled from “soft” to “loud”. Participants were instructed not to focus on singular events but on the stimuli as a whole to provide an overall impression of loudness.

Finally, participants indicated their music taste by rating how much they liked the music segments. They listened to the semi-compressed versions of the music segments and rated them on an absolute three-step scale (-1: do not like, 0: neutral, 1: like).

4.3.6 Results QUALITY For the statistical analysis, the IBM SPSS Statistic 22 software program was used. The quality ratings were subjected to a repeated-measures analysis of variance (ANOVA) with session (test, retest), condition (linear, semi-compressive, compressive), and genre (choir, opera, orchestra, pop, schlager) as within-subjects factors. In cases where sphericity was violated, Greenhouse-Geisser corrections were used if the epsilon test statistic was lower than 0.75; otherwise, the Huynh-Feldt corrections were

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applied as proposed by Girden (1992). There was no effect of session , = 0.115, = 0.737 ) but a significant effect of condition ( .,. = 21.09, < 0.001 ) and genre ( , = 2.705 , =

0.034 ) but. There were no interactions between session and condition ( .,. = 0.130, =

0.800 ), session and genre ( .,. = .728, = 0.514 ), or condition and genre .,. = 1.746, = 0.120 ). The linear condition was rated highest in quality (60.53) followed by the semi- compressive (54.30) and the compressive condition (47.43) (Figure 4:7). A Bonferroni-corrected post- hoc comparison of the conditions revealed significant differences between all pair-wise comparisons: linear vs. semi-compressive ( , = 13.08, = 0.001 ), linear vs. compressive ( , = 24.25, <

0.001 ), and semi-compressive vs. compressive ( , = 21.74, < 0.001 ).

DYNAMICS

For the data on dynamic range, the same statistical analysis was applied as for the data on quality.

There was no effect of session , = 0.067, = 0.798 ) but a significant effect of condition

( ., = 49.17, < 0.001 ) and genre ( .,. = 4.030, = 0.015 ). There was no interaction between session and condition ( .,. = 0.060, = 0.890 ) or session and genre ( .,. =

0.981, = 0.402 ) but a significant interaction between condition and genre (.,. = 3.47, = 0.014 ). The linear condition was rated largest in dynamic range (63.63), followed by the semi- compressive (52.32) and the compressive condition (43.88) (Figure 4:7). The mean difference scores are displayed in Figure 4:7. A Bonferroni-corrected post-hoc comparison of the conditions revealed that differences were significant for all pair-wise comparisons: linear vs. semi-compressive

(, = 51.73, < 0.001 ), linear vs. compressive ( , = 50.61, < 0.001 ), and semi- compressive vs. compressive ( , = 39.52, < 0.001 ). With regard to the interaction between condition and genre, the difference in perceived dynamic range between the linear and the compressive condition were largest for opera (Δ = 23.12) followed by orchestra (Δ = 21.02), choir (Δ = 20.01), pop (Δ = 18.55), and schlager (Δ = 16.05).

LOUDNESS

An ANOVA was carried out with condition (linear, semi-compressive, compressive) and genre (choir, opera, orchestra, pop, schlager) as within-subject factors.

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There was a significant effect of condition (.,. = 26.99, < 0.001 ) and genre ( .,. =

4.030, = 0.020 ) but no interaction between condition and genre ( .,. = 2.157, = 0.06). The linear condition was rated loudest (56.81), followed by the semi-compressive (51.35) and the compressive condition (47.94). A Bonferroni-corrected post-hoc comparison of the conditions revealed significant differences between all pair-wise comparisons: linear vs. semi-compressive

(, = 29.28, < 0.001 ), linear vs. compressive ( , = 14.68, = 0.001 ), and semi- compressive vs. compressive ( , = 28.11, < 0.001 ).

Figure 4:7 Ratings and standard errors for the data on dynamics, quality, and loudness in the linear, semi-compressive, and compressive condition.

4.3.7 Discussion

QUALITY

The findings confirmed the hypothesis that less compression benefits the perception of quality. The quality of the linearly processed stimuli was judged to be best, followed by the semi-compressive and the compressive setting. Against the background that the participants were acclimatized to hearing aids fitted with the compressive setting, the results appear even stronger. On the basis of the mere-

102 Chapter 4: Dynamics of Music and Perception of Dynamic Compression exposure effect (Zajonc 1968, Bradley 1971; Gordon & Holyoak 1983; Szpunar, Schellenberg, & Pliner 2004; Ishii 2005), we would expect a bias towards the compressive scheme that participants had grown accustomed to during the acclimatization period.

The results from this study are consistent with results from previous studies in confirming that less compression for music is beneficial for sound quality. A reason why the least compressive condition consistently yielded the best sound quality might be that the primary focus in music listening is enjoyment rather than intelligibility (Chasin & Russo 2004). Dynamic compression introduces distortion (Kates 2010). Listeners might be more sensitive to distortion introduced by compression in music than in speech. Therefore, the trade-off between audibility for soft parts and introducing distortion might shift towards less distortion and therefore to even less compression than the dynamic properties might suggest.

The optimal compression strength, however, varied on an individual level. Seven participants judged the quality of the semi-compressive or compressive processing superior to the linear processing. To understand the reason for these perceptual differences, participants were asked after the tests to verbally describe their subjective quality criteria. While instrument separation, liveliness, clarity, bandwidth, and intelligibility of lyrics were assessed as positive factors, inaudible passages or loudness peaks were mentioned as detrimental for sound quality. The latter criterion was shared among all four participants who gave the highest quality ratings for the compressive conditions.

DYNAMICS

The perception of dynamic differences between the linear, semi-compressive, and compressive conditions completely align with the experimental manipulations. Participants rated the linear version highest in dynamics, followed by the semi-compressed and the compressed versions. As the pairwise comparisons between versions were significant and there was also no effect of session, it can be assumed that participants reliably perceived differences between the three dynamic conditions. Furthermore, perceptual differences between the conditions varied across genre. The effect of compression was perceptually bigger for genres with a higher original dynamic range such as opera and orchestra than in less dynamic genres such as pop or schlager.

The fact that participants were asked to judge dynamic range as well as quality may have biased participants to consider quality in terms of dynamic range. We ran the repeated-measures ANOVA with

103 Chapter 4: Dynamics of Music and Perception of Dynamic Compression a between-subjects factor that divided the participants into two subsets: one subset contained the participants who started with evaluating differences in dynamic range (N=15) and the other subset contained the participants who started with evaluating differences in quality (N=16). The analysis revealed that the effect of order was not significant (.,. = 2.562, = 0.120 ).

LOUDNESS

Although loudness was equalized between conditions prior to the experiment using the DLM loudness model by Chalupper and Fastl (2002), participants rated the stimuli in the linear condition significantly louder than in the semi-compressed condition and softest in the compressed condition. Two reasons might have contributed to this deviation: First, our approach to average loudness in as proposed by Croghan, Arehart, and Kates (2012) might underestimate the long-term loudness perception of dynamic stimuli in hearing-impaired listeners. Second, loudness judgments for stimuli with a length of approximately ten seconds is extremely difficult. By design, the linear stimuli have the loudest passages but also the softest passages compared to the semi-compressive or compressive stimuli. Participants may overvalue loud passages when trying to determine an average for the overall loudness perception of the stimuli.

To outweigh a potential effect of loudness differences between conditions on quality ratings, an experimental post-hoc repeated-measures ANOVA was conducted in which the loudness scores were subtracted from the quality test scores. As with the original analysis, the differences in the linear condition were highest (3.75), followed by the semi-compressive (2.90) and the compressive condition (-0.16). The differences between conditions were significant ( .,. = 4.81 , p=0.022).

To further address the issue of a loudness bias being responsible for the advantage of the linear setting, a subgroup was formed from participants who did not perceive differences in long-term loudness between conditions after Bonferroni correction. The repeated-measures ANOVA was repeated and yielded the same results for dynamics ( ,. = 21.69 , p < 0.001) and quality ( .,. = 6.14 , p = 0.019) as the analysis for the whole group.

4.4 General Discussion The present study analyzed the dynamic range of an audio corpus of 1000 recorded songs and 28 monologue speech samples in quiet. A genre-specific analysis revealed that the recorded music sam-

104 Chapter 4: Dynamics of Music and Perception of Dynamic Compression ples of all genres generally had smaller dynamic ranges than the speech samples. As a consequence, a further study was conducted in which the compression of the NAL-NL2 prescription rule was compared with linear and semi-compressive processing. There was a significant trend that linear amplification yielded the best sound quality, followed by semi-compressive and compressive (NAL-NL2) processing.

The current study was based on recorded music. Live music, singing, or practicing an instrument are other situations in which music is consumed. Further research is required to analyze the acoustic properties in these auditory scenes and to adjust the dynamic compression in hearing aids accordingly. An ongoing challenge for hearing aids is the processing of high-level peaks that are often experienced in live music (e.g., Sivian, Dunn, & White 1931; Winckel 1962; Wilson et al. 1977; Cabot et al. 1978; Fielder 1982; Ahnert 1984).

The genre-based classification as performed in this study is one approach to organize music. Further fragmentation might reveal systematic differences in dynamic range within genres (e.g., baroque vs romantic orchestra music) that should be addressed by hearing-aid signal processing. Ideally, the compression parameters would adapt to individual songs or even adapt within a song. Streaming services could potentially incorporate information about the dynamic range so that the hearing aid can optimize the compression accordingly. A short delay in playback (look-ahead time) would also allow the possibility of continually adjusting the compression parameters to the input signal.

There is a secondary finding from the analysis of compression in recorded music that is also worth noting. As may be seen in Figure 4:1, the spectrum of the modern genres, speech, and the classical genres are distinct. The high frequencies are particularly prominent in the modern genres, followed by speech and then classical genres. Because of these differences, a single and universal multiband dynamic compression setting may apply too little gain for modern genres or too much gain for classical genres in the high-frequency bands. It may be beneficial for hearing-aid manufacturers to consider setting the compression curves differently for each of these three signal categories.

105 Chapter 4: Dynamics of Music and Perception of Dynamic Compression

Acknowledgments

We particularly want to thank Dr. Markus Hofbauer and Dr. Peter Derleth for their valuable support and our fruitful discussions. We further wish to thank the participants for taking part in this study and for appearing to each session as scheduled. We also thank our colleagues for letting us occupy the laboratory facilities for a long time of fitting and measurements.

The research protocol for this study was approved by grant (KEK-ZH. Nr. 2014-0520) from the Ethics Committee Zurich, Switzerland and was registered at http://clinicaltrials.gov (ID: NCT02373228).

Financial support for this research was provided by ETH Zürich, Phonak AG, and the Natural Sciences and Engineering Research Council of Canada.

106 Chapter 4: Dynamics of Music and Perception of Dynamic Compression

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Appendix

The following audio corpus was used in this chapter for the analysis of dynamic range:

Table 4:5 Audio corpus used for the dynamic range analysis sorted by genre and composer/interpret.

# Genre Composer / Interpret Title Release 1 Chamber Anton Bruckner Intermezzo for string quintet in D minor 2006 2 Chamber Bach Der Tag ist hin, die Sonne gehet nieder 2006 3 Chamber Bach Wenn wir in höchsten Nöthen 2006 4 Chamber Beethoven Cavatina. Adagio molto espressivo op 130 2006 5 Chamber Brahms No. 1 in C minor op 51.1 (1) Allegro 2012 6 Chamber Brahms No. 1 in C minor op 51.1 (2) Romanze. Poco Adagio 2012 7 Chamber Brahms No. 1 in C minor op 51.1 (4) Allegro 2012 8 Chamber Brahms No. 2 in A minor op 51.2 - (1) Allegro non troppo 2012 9 Chamber Brahms No. 2 in A minor op 51.2 - (2) Andante moderato 2012 No. 2 in A minor op 51.2 - (3) Quasi Minuetto, 10 Chamber Brahms 2012 moderato No. 2 in A minor op 51.2 - (4) Finale. Allegro non 11 Chamber Brahms 2012 assai 12 Chamber Brahms No. 3 in B-flat major op 67 (1) Vivace 2012 13 Chamber Brahms No. 3 in B-flat major op 67 (2) Andante 2012 No. 3 in B-flat major op 67 (4) Poco Allegretto con 14 Chamber Brahms 2012 Variazioni 15 Chamber Charles Ives Scherzo 2006 16 Chamber Haydn Variations on Gott erhalte Franz den Kaiser 2006 17 Chamber Hugo Wolf Intermezzo E-flat major 2006 No. 14 in G major ('Spring'), K. 387- Allegro vivace 18 Chamber Mozart 2012 assai No. 14 in G major ('Spring'), K. 387- Andante can- 19 Chamber Mozart 2012 tabile 20 Chamber Mozart No. 14 in G major ('Spring'), K. 387- Molto Allegro 2012 No. 15 in D Minor, K. 421 (K. 417b)- Allegretto ma 21 Chamber Mozart 2012 non troppo 22 Chamber Mozart No. 15 in D Minor, K. 421 (K. 417b)- Allegro 2012 23 Chamber Mozart No. 15 in D Minor, K. 421 (K. 417b)- Andante 2012 No. 16 in E-flat major, K 428 (421b) (1) Allegro non 24 Chamber Mozart 2012 troppo No. 16 in E-flat major, K 428 (421b) (2) Andante 25 Chamber Mozart 2012 con moto No. 16 in E-flat major, K 428 (421b) (4) Allegro 26 Chamber Mozart 2012 vivace No. 17 in B-flat major, K 458 'The Hunt' (1) Allegro 27 Chamber Mozart 2012 vivace assai No. 17 in B-flat major, K 458 'The Hunt' (2) 28 Chamber Mozart 2012 Menuetto and Trio moderato No. 17 in B-flat major, K 458 'The Hunt' (3) Adagio 29 Chamber Mozart 2012 in E-flat majo No. 17 in B-flat major, K 458 'The Hunt' (4) Allegro 30 Chamber Mozart 2012 assai 31 Chamber Mozart String Quartet No. 18 (1) in A major, K 464, Allegro 2011

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String Quartet No. 18 (2) in A major, K 464, 32 Chamber Mozart 2011 Menuetto String Quartet No. 18 (3) in A major, K 464, Andan- 33 Chamber Mozart 2011 te 34 Chamber Mozart String Quartet No. 18 (4) in A major, K 464, Allegro 2011 String Quartet No. 19 (1) in C major, K 465 'Disso- 35 Chamber Mozart 2011 nance', Adagio – Allegro String Quartet No. 19 (2) in C major, K 465 'Disso- 36 Chamber Mozart 2011 nance', Andante cantabile String Quartet No. 19 (3) in C major, K 465 'Disso- 37 Chamber Mozart 2011 nance', Allegro String Quartet No. 19 (4) in C major, K 465 'Disso- 38 Chamber Mozart 2011 nance', Menuetto. Allegro 39 Chamber Puccini Crisantemi 2006 40 Chamber Schubert Movement D 703 C minor 2006 41 Chamber Schubert No. 12 in C minor - Allegro assai 2012 42 Chamber Schubert No. 12 in C minor – Andante 2012 43 Chamber Schubert No. 13 in A minor – Andante 2012 44 Chamber Schubert No. 13 in A minor - Allegro moderato 2012 45 Chamber Schubert No. 13 in A minor - Allegro ma non troppo 2012 46 Chamber Schubert No. 14 in D minor – Allegro 2012 47 Chamber Schubert No. 14 in D minor - Andante con moto 2012 48 Chamber Schubert No. 14 in D minor - Presto 2012 49 Chamber Schubert No. 15 in G major - Allegro molto moderato 2012 50 Chamber Schubert No. 15 in G major - Andante un poco mosso 2012 51 Chamber Schubert No. 15 in G major - Allegro assai 2012 52 Chamber Schumann Op. 41 No. 1 Introduzione (Allegro) 2000 53 Chamber Schumann Op. 41 No. 1 Introduzione (Andante espressivo) 2000 54 Chamber Schumann Op. 41 No. 1 Scherzo (Presto - Intermezzo) 2000 55 Chamber Schumann Op. 41 No. 1 Adagio 2000 56 Chamber Schumann Op. 41 No. 1 Presto 2000 57 Chamber Schumann Op. 41 No. 2 Allegro vivace 2000 58 Chamber Schumann Op. 41 No. 2 Andante, quasi Variazioni 2000 59 Chamber Schumann Op. 41 No. 2 Scherzo (Presto) 2000 60 Chamber Schumann Op. 41 No. 2 Allegro molto vivace 2000 Op. 41 No. 3 Andante espressivo - Allegro molto 61 Chamber Schumann 2000 moderato 62 Chamber Schumann Op. 41 No. 3 - Scherzo - Assai agitato 2000 63 Chamber Schumann Op. 41, No. 3 - Adagio Molto 2000 64 Chamber Shostakovich Op. 68 No. 2 - Overture 2000 65 Chamber Shostakovich Op. 68 No. 2 - Recitative 2000 66 Chamber Shostakovich Op. 68 No. 2 - Valse 2000 67 Chamber Shostakovich Op. 68 No. 2 - Theme with Variations 2000 68 Chamber Shostakovich Op. 83 No. 4 - Allegretto 2000 69 Chamber Shostakovich Op. 83 No. 4 - Andantino 2000 70 Chamber Shostakovich Op. 83 No. 4 - Allegretto I 2000 71 Chamber Shostakovich Op. 83 No. 4 - Allegretto II 2000 72 Chamber Shostakovich Op. 92 No. 5 - Allegro non troppo 2000 73 Chamber Shostakovich Op. 92 No. 5 - Andante 2000 74 Chamber Shostakovich Op. 92 No. 5 - Moderato 2000 75 Chamber Shostakovich Op. 101 No. 6 - Allegretto 2000 76 Chamber Shostakovich Op. 101 No. 6 - Moderato con moto 2000 77 Chamber Shostakovich Op. 101 No. 6 - Lento 2000 78 Chamber Shostakovich Op. 101 No. 6 - Lento Allegretto 2000

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79 Chamber Shostakovich Op. 49 No. 1 – Moderato 2000 80 Chamber Shostakovich Op. 49 No. 1 – Moderato 2000 81 Chamber Shostakovich Op. 49 No. 1 - Allegro molto 2000 82 Chamber Shostakovich Op. 49 No. 1 – Allegro 2000 83 Chamber Shostakovich Op. 73 No. 3 – Allegretto 2000 84 Chamber Shostakovich Op. 73 No. 3 - Moderato con moto 2000 85 Chamber Shostakovich Op. 73 No. 3 - Allegro non troppo 2000 86 Chamber Shostakovich Op. 73 No. 3 – Adagio 2000 87 Chamber Shostakovich Op. 73 No. 3 – Moderato 2000 88 Chamber Villa Lobos No. 12 – Allegro 2000 89 Chamber Villa Lobos No. 12 - Andante Melancolico 2000 90 Chamber Villa Lobos No. 12 - Allegretto leggiero 2000 91 Chamber Villa Lobos No. 12 - Allegro - bem ritmado 2000 92 Chamber Villa Lobos No. 16 - Allegro non troppo 2000 93 Chamber Villa Lobos No. 16 - Molto andante 2000 94 Chamber Villa Lobos No. 16 - Vivace (Scherzo) 2000 95 Chamber Villa Lobos No. 16 - Molto allegro 2000 96 Chamber Villa Lobos No. 2 - Allegro non troppo 2000 97 Chamber Villa Lobos No. 2 - Scherzo. Allegro 2000 98 Chamber Villa Lobos No. 2 - Andante 2000 99 Chamber Villa Lobos No. 2 - Allegro deciso 2000 100 Chamber Wagner Albumblatt (1881) 2006 101 Choir Brahms Frauenchöre - Adoramus te 2003 102 Choir Brahms Op. 12 -Frauenchöre - Ave Maria 2003 Op. 27 - Frauenchöre Der 13.Psalm "Herr, 103 Choir Brahms 2003 wie lange" 104 Choir Brahms Frauenchöre - Der Gärtner 2003 Op. 37 - Frauenchöre - Drei geistliche Chöre - O 105 Choir Brahms 2003 bone Jesu Frauenchöre Gesang aus Ossians 106 Choir Brahms 2003 "Fingal" Frauenchöre Gesänge für Frauenchor, 2 Hörner 107 Choir Brahms 2003 und Harfe - Es tönt ein voller Harfenklang Op. 113 No. 1 - Frauenchöre Kanons - Göttlicher 108 Choir Brahms 2003 Morpheus Op. 113 No. 2 - Frauenchöre Kanons - Grausam 109 Choir Brahms 2003 erweist sich Amor am mi Op. 113 No. 3 - Frauenchöre Kanons - Sitzt ein 110 Choir Brahms 2003 schöns Vogerl aufm Dannabaum Op. 113 No. 4 - Frauenchöre Kanons - Schlaf, Kind- 111 Choir Brahms 2003 lein schlaf Op. 113 No. 5 - Frauenchöre Kanons - Wille, wille, 112 Choir Brahms 2003 will Op. 113 No. 6 - Frauenchöre Kanons - So lange 113 Choir Brahms 2003 Schönheit wird bestehn Op. 113 No. 7 - Frauenchöre Kanons - Wenn die 114 Choir Brahms 2003 Klänge nahn und fliehen Op. 113 No. 9 - Frauenchöre Kanons - Ans Auge des 115 Choir Brahms 2003 Liebsten Op. 113 No. 10 - Frauenchöre Kanons - Leise Töne 116 Choir Brahms 2003 der Brust Op. 113 No. 11 - Frauenchöre Kanons - Ich weiss 117 Choir Brahms 2003 nicht was im Hain die Taube girret 118 Choir Brahms Frauenchöre Lied 2003

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119 Choir Brahms Frauenchöre Regina coeli 2003 120 Choir Brahms Geistliche Werke, Lieder -Freiwillig her! 2003 Op. 44 - Geistliche Werke, Lieder 12 Lieder und 121 Choir Brahms 2003 Romanzen für Frauenchor - Minnelied 122 Choir Brahms Op. 44 - Geistliche Werke, Lieder Barcarole 2003 123 Choir Brahms Op.44 - Geistliche Werke, Lieder Der Bräutigam 2003 124 Choir Brahms Op. 95 - Lieder - Der Jäger 2003 125 Choir Brahms Op.44 - Geistliche Werke, Lieder Die Müllerin 2003 Op. 109 - Geistliche Werke, Lieder Fest- und Ge- 126 Choir Brahms 2003 denksprüche - Unsere Vöter hofften auf dich Op. 41 - Geistliche Werke, Lieder Fünf Lieder für 127 Choir Brahms 2003 Männerchor - Ich schwing mein Horn 128 Choir Brahms Geistliche Werke, Lieder Gebt Acht! 2003 129 Choir Brahms Geistliche Werke, Lieder Geleit 2003 130 Choir Brahms Geistliche Werke, Lieder Magdalena 2003 131 Choir Brahms Geistliche Werke, Lieder Marias Kirchgang 2003 132 Choir Brahms Geistliche Werke, Lieder Marias Lob 2003 Op. 22 - Geistliche Werke, Lieder Marienlieder - 133 Choir Brahms 2003 Der englische Gruß 134 Choir Brahms Geistliche Werke, Lieder Marschieren 2003 135 Choir Brahms Geistliche Werke, Lieder Narias Wallfahrt 2003 136 Choir Brahms Geistliche Werke, Lieder Ruf zur Maria 2003 Geistliche Werke, Lieder Wenn ein starker Ge- 137 Choir Brahms 2003 wappneter 138 Choir Brahms Geistliche Werke, Lieder Wo ist ein so herrlich Volk 2003 Op. 29 - Zwei Motetten - Es ist das Heil uns kom- 139 Choir Brahms 2003 men her 140 Choir Brahms Motetten - Schaffe in mir, Gott 2003 141 Choir Brahms Op. 30 - Motetten - Geistliches Lied 2003 142 Choir Brahms Op. 74 - Motetten - Warum ist das Licht gegeben 2003 143 Choir Brahms Motetten - O Heiland, reib die Himmel auf 2003 144 Choir Brahms Op. 110 - Motetten - Ich aber bin elend 2003 145 Choir Brahms Motetten - Ach arme Welt, du trugest mich 2003 146 Choir Brahms Motetten - Wenn wir ir hochsten Noten sein 2003 147 Choir Brahms WoO 18 - Motetten - Missa canonica - Kyrie 2003 148 Choir Brahms Motetten – Sanctus 2003 149 Choir Brahms Motetten – Benedictus 2003 150 Choir Brahms Motetten - Agnus Dei 2003 151 Choir Brahms WoO 34 - Volkslieder - Von edler Art 2003 152 Choir Brahms Volkslieder - Mit Lust tät ich ausreiten 2003 153 Choir Brahms Volkslieder - Bei nächtlicher Weil 2003 154 Choir Brahms Volkslieder - Vom hieligen Mätyrer Emmerano 2003 155 Choir Brahms Volkslieder - Täublein weiß 2003 156 Choir Brahms Volkslieder - Ach lieber Herre Jesu Christ 2003 157 Choir Brahms Volkslieder - St.Raphael 2003 158 Choir Brahms Volkslieder - In stiller Nacht 2003 159 Choir Brahms Volkslieder - Abschiedslied 2003 160 Choir Brahms Volkslieder - Der tote Knabe 2003 161 Choir Brahms Volkslieder - Die Wollust im Maien 2003 162 Choir Brahms Volkslieder - Morgengesnag 2003 163 Choir Brahms Volkslieder - Schnitter Tod 2003 164 Choir Brahms Volkslieder - Der englische Jäger 2003 165 Choir Brahms WoO 35 - Volkslieder - Scheiden 2003 166 Choir Brahms Volkslieder - Wach auf! 2003

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167 Choir Brahms Volkslieder - Erlaube mir 2003 168 Choir Brahms Volkslieder - Der Fiedler 2003 169 Choir Brahms Volkslieder - Da unten im Tale 2003 170 Choir Brahms Volkslieder - Des Abends 2003 171 Choir Brahms Volkslieder - Wach auf!(".Bearbeitung) 2003 172 Choir Brahms Volkslieder - Dort in den Weiden 2003 173 Choir Brahms Volkslieder - Altes Volkslied 2003 174 Choir Brahms Volkslieder - Der Ritter und die Fein 2003 175 Choir Brahms Volkslieder - Der Zimmergesell 2003 176 Choir Mendelssohn Choralharmonisierungen - Das deutsche Gloria 2002 Choralharmonisierungen - Wie schön leuchtet der 177 Choir Mendelssohn 2002 Morgenstern 178 Choir Mendelssohn Choralharmonsierungen - Vom Himmel hoch 2002 179 Choir Mendelssohn Christe eleison 2002 Jube Domine, for soloists & douple chorus in C 180 Choir Mendelssohn 2002 major 181 Choir Mendelssohn Kyrie eleison (2nd) 2002 182 Choir Mendelssohn Kyrie eleison 2002 183 Choir Mendelssohn Psalm 100 2002 184 Choir Mendelssohn Psalm 2 2002 185 Choir Mendelssohn Psalm 31 - Defend me, Lord 2002 186 Choir Mendelssohn Psalm 5 - Lord hear the voice 2002 187 Choir Mendelssohn Psalm 91 2002 188 Choir Mendelssohn Psalmen 98 2002 189 Choir Mendelssohn Op. 69 No. 3 - Mein Herz erhebet 2002 190 Choir Mendelssohn Op. 23 No. 3 - Mitten wir im Leben (1st) 2002 Op. 69 No. 1 - Herr nun lassest du deinen Diener in 191 Choir Mendelssohn 2002 Frieden fahren 192 Choir Mendelssohn Op. 69 No. 2 - Jauchzet 2002 193 Choir Mendelssohn Op. 23 No. 1 - Aus tiefer Not schrei ich zu dir (1st) 2002 194 Choir Mendelssohn Op. 23 No. 1 - Aus tiefer Not schrei ich zu dir (2nd) 2002 195 Choir Mendelssohn Op. 23 No. 2 - Ave Maria (2nd) 2002 196 Choir Mendelssohn Op. 23 No. 2 - Ave Maria (3rd) 2002 197 Choir Mendelssohn Op. 23 No. 2 - Ave Maria (4th) 2002 198 Choir Mendelssohn Op. 23 No. 3 - Mitten wir im Leben (2nd) 2002 199 Choir Mendelssohn Op. 23 No. 3 - Mitten wir im Leben (3rd) 2002 200 Choir Mendelssohn Op. 23 No. 3 - Mitten wir im Leben (4th) 2002 Carmen - Act 1 - Attention! Chut! Attention! Tai- 201 Opera Bizet 2003 sons-Nous! 202 Opera Bizet Carmen - Act 1 - L'Amour Est Un Oiseau Rebelle 2003 Carmen - Act 1 - Mais Nous Ne Voyons Pas La Car- 203 Opera Bizet 2003 mencita!...Quand Je Vous Aimerai? Carmen - Act 1 - Que Se Passe-T-Il Donc Là- 204 Opera Bizet 2003 Bas?...Au Secours! Au Secours! 205 Opera Bizet Carmen - Act 1 - Regardez Donc Cette Petite 2003 206 Opera Bizet Carmen - Act 1 - Sur La Place Chacun Passe 2003 207 Opera Bizet Carmen - Act 1 - Voici L'Ordre...Partez 2003 Carmen - Act 2 - Enfin, C'Est Toi!... Je Vais Danser 208 Opera Bizet 2003 En Votre Honneur 209 Opera Bizet Carmen - Act 2 - Halte Là! Qui Va Là? 2003 Carmen - Act 2 - La-La-La-La... Attends Un Peu, 210 Opera Bizet 2003 Carmen 211 Opera Bizet Carmen - Act 2 - Les Tringles Des Sistres Tintaient 2003 212 Opera Bizet Carmen - Act 2 - Messieurs, Pastia Me Dit... 2003

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Carmen - Act 2 - Plus Tard!... La Guerre, C'Est Là? 213 Opera Bizet 2003 Guerre! 214 Opera Bizet Carmen - Act 3 - Je Dis Que Rien Ne M'Épouvante 2003 215 Opera Bizet Carmen - Act 3 - Notre Metier Est Bon 2003 Carmen - Act 3 - Quant Au Douanier, C'Est Notre 216 Opera Bizet 2003 Affaire 217 Opera Bizet Carmen - Act 3 - Toreador, En Garde! 2003 218 Opera Bizet Carmen - Act 4 - A Deux Cuartos! 2003 219 Opera Bizet Carmen - Act 4 - C'Est Toi!, C'Est Moi! 2003 220 Opera Bizet Carmen - Act 4 - Ou-Vas-Tu?, Laisse-Moi! 2003 221 Opera Mozart Don Giovanni - Akt 1 - manco Male, E Partita 2007 222 Opera Mozart Don Giovanni - Akt 1 - ho Capito, Signor si 2007 223 Opera Mozart Don Giovanni - Akt 1 - alfin Siam Liberati 2007 224 Opera Mozart Don Giovanni - Akt 1 - la Ci Darem La Mano 2007 225 Opera Mozart Don Giovanni - Akt 1 - leporello, Ove Sei 2007 226 Opera Mozart Don Giovanni - Akt 1 - fuggi, Crudele, Fuggi 2007 227 Opera Mozart Don Giovanni - Akt 1 - orsu, Spicciati Presto 2007 228 Opera Mozart Don Giovanni - Akt 1 - udisti, Qualche Bella 2007 229 Opera Mozart Don Giovanni - Akt 1 - chi E la 2007 Don Giovanni - Akt 1 - madamina, Il Catalogo E 230 Opera Mozart 2007 Questo Don Giovanni - Akt 1 - giovinette, Che Fate All'amo- 231 Opera Mozart 2007 re 232 Opera Mozart Don Giovanni - Akt 2 (1) xxx 2007 Don Giovanni - Akt 2 - don Giovanni, A Cenar Teco 233 Opera Mozart 2007 M'invitasti 234 Opera Mozart Don Giovanni - Akt 2 - ah, Dove Il Perfido 2007 235 Opera Mozart Don Giovanni - Akt 2 - leoprello 2007 236 Opera Mozart Don Giovanni - Akt 2 - ah Taci, Ingiusto Core 2007 237 Opera Mozart Don Giovanni - Akt 2 - amico, Che Ti Pa 2007 238 Opera Mozart Don Giovanni - Akt 2 - deh, Vieni Alla Finestra 2007 239 Opera Mozart Don Giovanni - Akt 2 - Ve Gente Alla Finestra 2007 240 Opera Mozart Don Giovanni - Akt 2 - meta Di Voi Qua Vadano 2007 Zauberflöte - Akt 1 - Du feines Täubchen nun her- 241 Opera Mozart 2010 ein Zauberflöte - Akt 1 - Bei Männern, welche Liebe 242 Opera Mozart 2010 fühlen Zauberflöte - Akt 1 - Zum Ziele führt dich diese 243 Opera Mozart 2010 Bahn Zauberflöte - Akt 1 - Die Weisheitslehre dieser 244 Opera Mozart 2010 Knaben Zauberflöte - Akt 1 - Wie stark ist nicht dein Zau- 245 Opera Mozart 2010 berton 246 Opera Mozart Zauberflöte - Akt 1 - Ha! Ha! nun doch erwischt 2010 247 Opera Mozart Zauberflöte - Akt 1 - Es lebe Sarastro. Sarastro lebe 2010 Zauberflöte - Akt 1 - Da, stolzer Jüngling nur hier- 248 Opera Mozart 2010 her Zauberflöte - Akt 1 - Zu Hilfe! Zu Hilfe! - Dialog Wo 249 Opera Mozart 2010 bin ich 250 Opera Mozart Zauberflöte - Akt 1 - Was hör ich 2010 Zauberflöte - Akt 1 - Dies Bildnis ist bezaubernd 251 Opera Mozart 2010 schön 252 Opera Mozart Zauberflöte - Akt 1 - O zitre nicht mein lieber Sohn 2010 253 Opera Mozart Zauberflöte - Akt 1 - Hm! hm! hm! hm! 2010

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Zauberflöte - Akt 2 - Morden soll ich.. Herr strafe 254 Opera Mozart 2010 meine Mutter nichts Zauberflöte - Akt 2 - Der Hölle Rache kocht in mei- 255 Opera Mozart 2010 nem Herzen Zauberflöte - Akt 2 - Ach ich fühl es ist verschwun- 256 Opera Mozart 2010 den 257 Opera Mozart Zauberflöte - Akt 2 - Wie Wie Wie 2010 Zauberflöte - Akt 2 - Ein Küsschen denke ich liesse 258 Opera Mozart 2010 sich entschuldigen Zauberflöte - Akt 2 - Seid uns zum zweiten Mal 259 Opera Mozart 2010 willkommen Zauberflöte - Akt 2 - Tamino ich kann auch schwei- 260 Opera Mozart 2010 gen wenns sein muss Boris Godunov - Act 1 - Nye Syétuy, Brat, Shot 261 Opera Mussorgsky 2002 Ráno Gréshny Svyet Pokinu Boris Godunov - Act 1 - Ty Vsyo Pisál I Snom Nye 262 Opera Mussorgsky 2002 Pozabylsa 263 Opera Mussorgsky Boris Godunov - Act 1 - Ya Grámotny 2002 Boris Godunov - Act 1 - Yeshchó Odnó Poslyédneye 264 Opera Mussorgsky 2002 Skazánye Boris Godunov - Act 2 - Chevó? Al Lyúty Zvyar 265 Opera Mussorgsky 2002 Nasyédku Vspolokhnul? 266 Opera Mussorgsky Boris Godunov - Act 2 - Ekh, Máma Mámushka 2002 267 Opera Mussorgsky Boris Godunov - Act 2 - Gdye Ty, Zheníh Moy 2002 268 Opera Mussorgsky Boris Godunov - Act 2 Kak Komár Drová Rubíl 2002 Boris Godunov - Act 2 - Ny, Shto?...Pópinka Nash 269 Opera Mussorgsky 2002 Sidyél 270 Opera Mussorgsky Boris Godunov - Act 2 - Shto Takóe? 2002 271 Opera Mussorgsky Boris Godunov - Act 2 - Slikhál Li Ty, Kogdá-Nibud' 2002 Boris Godunov - Act 2 - Uf! Tyazheló! Day Dukh 272 Opera Mussorgsky 2002 Perevedú... Boris Godunov - Act 2 - V Ugliche, V Soboryé, Pred 273 Opera Mussorgsky 2002 Vsyém Naródom Boris Godunov - Act 2 - Velíky Gosudár, Chelóm 274 Opera Mussorgsky 2002 Byu 275 Opera Mussorgsky Boris Godunov - Act 3 - Shto Dyérzky Izhets! 2002 Boris Godunov - Prologue - Na Kovó Ty Nas Pok- 276 Opera Mussorgsky 2002 idáesh Boris Godunov - Prologue - Pravolslávnyyel Nye 277 Opera Mussorgsky 2002 Umolím Boyárin! 278 Opera Mussorgsky Boris Godunov - Prologue - Skorbít Dushá! 2002 Boris Godunov - Prologue - Sláva Tebyé, Tvortsú 279 Opera Mussorgsky 2002 Vsevyshnemu, Na Zemli! 280 Opera Mussorgsky Boris Godunov - Prologue - Sláva, Sláva, Sláva! 2002 281 Opera Strauss Rosenkavalier - Akt 1 - Was soll denn die 2001 282 Opera Strauss Rosenkavalier - Akt 1 - I komm glei 2001 283 Opera Strauss Rosenkavalier - Akt 1 - Di Rigori Armato il seno 2001 284 Opera Strauss Rosenkavalier - Akt 1 - Wie du warst 2001 285 Opera Strauss Rosenkavalier - Akt 1 - Er soll jetzt gehn 2001 286 Opera Strauss Rosenkavalier - Akt 1 - Lachst du mich aus 2001 287 Opera Strauss Rosenkavalier - Akt 1 - Und ich, ich sitz hier 2001 Rosenkavalier - Akt 1 - Natürlich muss ich vorher 288 Opera Strauss 2001 den Bräutigam 289 Opera Strauss Rosenkavalier - Akt 1 - Hat sie schon einmal mit 2001

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einem Kavalier Rosenkavalier - Akt 2 - Ohne mich, ohne mich, 290 Opera Strauss 2001 jeder Tag so ein Bang 291 Opera Strauss Rosenkavalier - Akt 2 - In dieser feierlichen Stunde 2001 292 Opera Strauss Rosenkavalier - Akt 2 - Mir ist die Ehre widerfahren 2001 293 Opera Strauss Rosenkavalier - Akt 2 - Oh war ich schon einmal 2001 294 Opera Strauss Rosenkavalier - Akt 3 - Bin glücklich über Massen 2001 295 Opera Strauss Rosenkavalier - Akt 3 - Ihr seht Herr Kommissar 2001 296 Opera Strauss Rosenkavalier - Akt 3 - Leopold wir gengan 2001 Rosenkavalier - Akt 3 - Habn euer Gnaden noch 297 Opera Strauss 2001 weitere Befehle 298 Opera Strauss Rosenkavalier - Akt 3 - Er ists, er ists 2001 299 Opera Strauss Rosenkavalier - Akt 3 - Halt! Keiner rührt sich 2001 Rosenkavalier - Akt 3 - Zur Stelle! Was wird von mir 300 Opera Strauss 2001 gewünscht 301 Orchestra Beethoven No. 6 - Allegro ma non troppo 2002 302 Orchestra Beethoven No. 6 - Andante molto mosso 2002 303 Orchestra Beethoven No. 6 - Allegro (1st) 2002 304 Orchestra Beethoven No. 6 - Allegro (2nd) 2002 305 Orchestra Beethoven No. 6 - Allegretto 2002 306 Orchestra Beethoven No. 8 - Allegro vivace e con brio 2002 307 Orchestra Beethoven No. 8 - Allegretto scherzando 2002 308 Orchestra Beethoven No. 8 - Tempo di Menuetto 2002 309 Orchestra Beethoven No. 8 - Allegro vivace 2002 Claudio Abbado Men- 310 Orchestra Op. 90 No. 4 - La Majeur - Allegro vivace 2009 delssohn Claudio Abbado Men- 311 Orchestra Op. 90 No. 4 - La Majeur - Andante con moto 2009 delssohn Claudio Abbado Men- 312 Orchestra Op. 90 No. 4 - La Majeur - Con moto moderato 2009 delssohn Claudio Abbado Men- 313 Orchestra Op. 90 No. 4 - La Majeur - Saltarello. Presto 2009 delssohn Claudio Abbado Men- 314 Orchestra Op. 107 No. 5 - Ré Majeur - Allegro vivace 2009 delssohn Claudio Abbado Men- 315 Orchestra Op. 107 No. 5 - Ré Majeur - Andante 2009 delssohn Claudio Abbado Men- Op. 107 No. 5 - Ré Majeur - Andante con moto - 316 Orchestra 2009 delssohn Allegro maestoso Claudio Abbado Men- Op. 107 No. 5 - Ré Majeur - Andante. Allegro con 317 Orchestra 2009 delssohn fuoco 318 Orchestra Mendelssohn Op. 11 No. 1 in C minor - Allegro ci molto 2009 319 Orchestra Mendelssohn Op. 11 No. 1 in C minor - Allegro con fuoco 2009 320 Orchestra Mendelssohn Op. 11 No. 1 in C minor - Andante 2009 321 Orchestra Mendelssohn Op. 11 No. 1 in C minor - Menuetto, Allegro molto 2009 322 Orchestra Mendelssohn Op. 56 No. 3 in A minor ('Scottish') - Adagio 2009 Op. 56 No. 3 in A minor ('Scottish') - Allegro viva- 323 Orchestra Mendelssohn 2009 cissimo - Allegro maesto assai Op. 56 No. 3 in A minor ('Scottish') - Andante con 324 Orchestra Mendelssohn 2009 moto - allegro un poco agitato - Assai animato Op. 56 No. 3 in A minor ('Scottish') - Vivace non 325 Orchestra Mendelssohn 2009 troppo 326 Orchestra Mozart Sinfonie Nr. 38 D-Dur KV 504 ('Prager') - 2. Andante 2002 Sinfonie Nr. 39 Es-Dur KV 543 - 2. Andante con 327 Orchestra Mozart 2002 meto

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328 Orchestra Mozart Sinfonie Nr. 39 Es-Dur KV 543 - 4. Allegro 2002 329 Orchestra Mozart Allegro KV128 2002 330 Orchestra Mozart Allegro KV129 2002 331 Orchestra Mozart Presto KV124 2002 332 Orchestra Mozart Symphonie KV114 2002 333 Orchestra Mozart Symphonie No. 15 in G major KV 124 - Allegro 2002 334 Orchestra Mozart Symphonie No. 17 in G major KV 129 - Allegro 2002 Symphonie No. 12 in G major KV 110 (2nd) - Alle- 335 Orchestra Mozart 2002 gro 336 Orchestra Mozart Symphonie No. 12 in G major KV 110 - Allegro 2002 Symphonie No. 13 in F major KV 112 - Menuetto & 337 Orchestra Mozart 2002 trio 338 Orchestra Mozart Symphonie No. 8 D major KV 48 - Andante 2002 339 Orchestra Mozart Symphonie No. 9 C major KV 73 - Allegro 2002 340 Orchestra Mozart Symphonie No. 9 C major KV 73 - Molto allegro 2002 341 Orchestra Mozart Symphony No. 18 KV 130 - Allegro 2002 342 Orchestra Mozart Symphony No. 18 KV 130 - Molto Allegro 2002 343 Orchestra Mozart Symphony No. 19 KV 132 - Menuetto 2002 344 Orchestra Mozart Symphony No. 25 KV 183 - Andante 2002 345 Orchestra Mozart Symphony KV 111a - Allegro 2002 346 Orchestra Mozart Symphony No. 33 in Bflat major - Menuetto 2002 Symphony No. 34 in C major - Andante di molto piu 347 Orchestra Mozart 2002 tosto allegretto 348 Orchestra Mozart Symphony No. 35 in D major - Andante 2002 349 Orchestra Mozart Symphony No. 1 in E flat major - Molto Allegro 2002 Symphony No. 27 in G major KV 199 - Andantino 350 Orchestra Mozart 2002 grazioso 351 Orchestra Mozart Symphony No. 28 in G major KV 200 - Andante 2002 Symphony No. 30 in D major KV 202 - Molto alle- 352 Orchestra Mozart 2002 gro 353 Orchestra Mozart Symphony No. 30 in D major KV 202 - Presto 2002 354 Orchestra Mozart Symphony No. 4 in D major - Allegro 2002 355 Orchestra Mozart Symphony No. 45 in D major - Menuetto & trio 2002 356 Orchestra Mozart Symphony No. 5 in B flat major - Allegro 2002 357 Orchestra Mozart Symphony No. 6 in F major (2nd) - Allegro 2002 358 Orchestra Mozart Symphony No. 6 in F major - Allegro 2002 359 Orchestra Mozart Symphony in F major - Allegro assai 2002 360 Orchestra Mozart Symphony No. 31 in D K297 'Paris' I Allegro assai 2002 Symphony No. 36 in C K425 'Linz' I Adagio - Allegro 361 Orchestra Mozart 2002 con spirito 362 Orchestra Mozart Symphony No. 36 in C K425 'Linz' IV Presto 2002 363 Orchestra Mozart Symphony No. 40 in G minor K550 III Menuetto 2002 364 Orchestra Mozart Symphony KV 550 551 'Jupiter' No. 404 2002 365 Orchestra Mozart Symphony KV 550 551 'Jupiter' No. 401 2002 366 Orchestra Mozart Symphony, KV 550 551 'Jupiter' No. 413 2002 Op. 30 - Also sprach Zarathustra (Thus Spoke Zoro- 367 Orchestra Richard Strauss 2001 aster), tone poem for orchestra - Dirge Op. 30 - Also sprach Zarathustra (Thus Spoke Zoro- 368 Orchestra Richard Strauss aster), tone poem for orchestra - Of Joys and Pas- 2001 sions Op. 30 - Also sprach Zarathustra (Thus Spoke Zoro- 369 Orchestra Richard Strauss 2001 aster), tone poem for orchestra - Of Science Op. 30 - Also sprach Zarathustra (Thus Spoke Zoro- 370 Orchestra Richard Strauss 2001 aster), tone poem for orchestra - Of The Great

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Longing Op. 30 - Also sprach Zarathustra (Thus Spoke Zoro- 371 Orchestra Richard Strauss 2001 aster), tone poem for orchestra - Sunrise Op. 30 - Also sprach Zarathustra (Thus Spoke Zoro- 372 Orchestra Richard Strauss 2001 aster), tone poem for orchestra - The Dance Song Op. 40 - Ein Heldenleben (A Hero's Life), tone po- 373 Orchestra Richard Strauss 2001 em for orchestra - The Hero's Adversaries Op. 40 - Ein Heldenleben (A Hero's Life), tone po- 374 Orchestra Richard Strauss 2001 em for orchestra - The Hero's Work Of Peace Op. 40 - Ein Heldenleben, tone poem for orchestra 375 Orchestra Richard Strauss - The Hero's Retreat From The World And Fulfill- 2001 ment 376 Orchestra Smetana Aus Böhmens Hain und Flur 2007 377 Orchestra Smetana Blaník 2007 378 Orchestra Smetana Die Moldau 2007 379 Orchestra Smetana Scharka 2007 380 Orchestra Smetana Tábor 2007 381 Orchestra Smetana Vysehrad 2007 Ma Vlast - Prague Carnival, Introduction & Polo- 382 Orchestra Smetana 2007 naise 383 Orchestra Smetana Ma Vlast - Allegro vivace 2007 Ma Vlast - Doktor Faust Overture to the puppet 384 Orchestra Smetana 2007 play by Matej Kopecky 385 Orchestra Smetana Ma Vlast - Festive Overture, in C major 2007 386 Orchestra Smetana Ma Vlast - Festive Overture, in D major 2007 387 Orchestra Smetana Ma Vlast - Finale, allegro non troppo ma energico 2007 388 Orchestra Smetana Ma Vlast - Hakon Jarl, Synphonic Poem 2007 389 Orchestra Smetana Ma Vlast - Largo maestoso 2007 390 Orchestra Smetana Ma Vlast - March of the National Guard 2007 391 Orchestra Smetana Ma Vlast - Nasim Devam, To our Girls, Polka 2007 392 Orchestra Smetana Ma Vlast - Overture to The Bartered Bride 2007 393 Orchestra Smetana Ma Vlast - Richard III, Symphonic Poem 2007 394 Orchestra Smetana Ma Vlast - Scherzo, allegro vivace 2007 395 Orchestra Smetana Ma Vlast - Shakespeare Festival March 2007 396 Orchestra Smetana Ma Vlast - The Bartered Bride Furiant 2007 397 Orchestra Smetana Ma Vlast - The Bartered Bride Skocna 2007 398 Orchestra Smetana Ma Vlast - The Bartered Bride, Polka 2007 399 Orchestra Smetana Ma Vlast - Venkovanka, the Peasant Woman, Polka 2007 400 Orchestra Smetana Ma Vlast - Wallenstein's Camp, Symphonic Poem 2007 Op. 31 No. 2 - Sonata for piano in D major - Adagio 401 Piano Dussek 2005 con espressione Op. 31 No. 2 - Sonata for piano in D major- Allegro 402 Piano Dussek 2005 non tanto Op. 31 No. 2 - Sonata for piano in D major - Pasto- 403 Piano Dussek 2005 rale. Allegro non troppo Op. 35 No. 1 - Sonata in B flat major - Allegro mo- 404 Piano Dussek 2005 derato e maestoso Op. 35 No. 1 - Sonata in B flat major - Finale. Alle- 405 Piano Dussek 2005 gro non troppo ma con spirito 406 Piano Dussek Op. 35 No. 1 - Sonata in B flat major - Introduzione 2005 Op. 35 No. 3 - Sonata in C minor - Adagio patetico 407 Piano Dussek 2005 ed espressivo Op. 35 No. 3 - Sonata in C minor - Allegro agitato 408 Piano Dussek 2005 assai

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Op. 35 No. 3 - Sonata in C minor - Intermezzo. 409 Piano Dussek 2005 Presto 410 Piano Dussek Op. 35 No. 2 - Sonata in G major - Allegro 2005 Op. 35 No. 2 - Sonata in G major - Rondo. Molto 411 Piano Dussek 2005 allegro con espressione Sonate Piano-forte Hob.XVI-48 - Andante con 412 Piano Haydn 2005 espressione 413 Piano Haydn Sonate Piano-forte Hob XVI- 48 - Rondo- Presto 2005 414 Piano Haydn Sonate Piano-forte Hob.XVI-49 - Allegro 2005 415 Piano Haydn Sonate Piano-forte Hob.XVI-49 - Adagio e cantabile 2005 Sonate Piano-forte Hob.XVI-49 - Finale. Tempo di 416 Piano Haydn 2005 Minuetto 417 Piano Haydn Sonate Piano-forte Hob.XVI-50 - Allegro 2005 418 Piano Haydn Sonate Piano-forte Hob.XVI-50 - Adagio 2005 419 Piano Haydn Sonate Piano-forte Hob.XVI-50 - Allegro molto 2005 420 Piano Haydn Sonate Piano-forte Hob.XVI-51 - Andante 2005 421 Piano Haydn Sonate Piano-forte Hob.XVI-51 - Finale. Presto 2005 422 Piano Haydn Sonate Piano-forte Hob.XVI-52 - Allegro 2005 423 Piano Haydn Sonate Piano-forte Hob.XVI-52 - Adagio 2005 424 Piano Haydn Sonate Piano-forte Hob.XVI-52 - Finale. Presto 2005 Auenbrugger Sonata C major, Hob.XVI-35 - Allegro 425 Piano Haydn 2008 con brio Auenbrugger Sonata C major, Hob.XVI-35 - Finale. 426 Piano Haydn 2008 Allegro Auenbrugger Sonata C sharp minor, Hob.XVI-36 - 427 Piano Haydn 2008 Scherzando. Allegro con brio Auenbrugger Sonata D major, Hob.XVI-37 - Allegro 428 Piano Haydn 2008 con brio Auenbrugger Sonata D major, Hob.XVI-37 - Finale. 429 Piano Haydn 2008 Presto ma non troppo Auenbrugger Sonata E flat major, Hob.XVI-38 - 430 Piano Haydn 2008 Adagio Auenbrugger Sonata G major, Hob.XVI-39 - Allegro 431 Piano Haydn 2008 con brio Auenbrugger Sonata G major, Hob.XVI-39 - Prestis- 432 Piano Haydn 2008 simo 433 Piano Haydn Bossler Sonatas No. 54 - Allegro innocente 2008 434 Piano Haydn Bossler Sonatas No. 54 – Presto 2008 435 Piano Haydn London Sonata C major, Hob.XVI-50 - Adagio 2008 436 Piano Haydn London Sonata C major, Hob.XVI-50 - Allegro 2008 437 Piano Haydn London Sonata C major, Hob.XVI-50 - Allegro molto 2008 438 Piano Haydn London Sonata D major, Hob.XVI-51 - Andante 2008 439 Piano Haydn London Sonata D major, Hob.XVI-51 - Finale. Presto 2008 London Sonata E flat major, Hob.XVI-49 - Adagio e 440 Piano Haydn 2008 cantabile 441 Piano Haydn London Sonata E flat major, Hob.XVI-49 - Allegro 2008 London Sonata E flat major, Hob.XVI-49 - Finale. 442 Piano Haydn 2008 Tempo di Menuet 443 Piano Haydn London Sonata E flat major, Hob.XVI-52 - Adagio 2008 London Sonata E flat major, Hob.XVI-52 - Allegro 444 Piano Haydn 2008 (moderato) London Sonata E flat major, Hob.XVI-52 - Finale. 445 Piano Haydn 2008 Presto 446 Piano Mozart Fantasia for piano in C minor, K. 475 2006

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Piano Sonata No. 1 in C major, K. 279 (K. 189d) – 447 Piano Mozart 2006 Allegro Piano Sonata No. 10 in C major, K. 330 (K. 300h) - 448 Piano Mozart 2006 Andante cantabile Piano Sonata No. 11 in A major ('Alla Turca') K. 331 449 Piano Mozart 2006 (K. 300i) - Alla Turca, Allegretto Piano Sonata No. 12 in F major, K. 332 (K. 300k) – 450 Piano Mozart 2006 Adagio Piano Sonata No. 13 in B flat major, K. 333 (K. 451 Piano Mozart 2006 315c) - Allegretto grazioso Piano Sonata No. 13 in B flat major, K. 333 (K. 452 Piano Mozart 2006 315c) - Andante cantabile 453 Piano Mozart Piano Sonata No. 14 in C minor, K. 457 - Adagio 2006 454 Piano Mozart Piano Sonata No. 14 in C minor, K. 457 - Allegro 2006 Piano Sonata No. 14 in C minor, K. 457 - Molto 455 Piano Mozart 2006 allegro Piano Sonata No. 15 in C major ('Sonata semplice') 456 Piano Mozart 2006 K. 545 - Andante Piano Sonata No. 15 in C major ('Sonata semplice') 457 Piano Mozart 2006 K. 545 - Rondo, Allegretto 458 Piano Mozart Piano Sonata No. 16 in B flat major, K. 570 - Adagio 2006 Piano Sonata No. 16 in B flat major, K. 570 - Alle- 459 Piano Mozart 2006 gretto 460 Piano Mozart Piano Sonata No. 16 in B flat major, K. 570 - Allegro 2006 Piano Sonata No. 3 in B flat major, K. 281 (K.189f) – 461 Piano Mozart 2006 Allegro Piano Sonata No. 4 in E flat major, K. 282 (K. 189g) 462 Piano Mozart 2006 - Menuetto I & II Piano Sonata No. 5 in G major, K. 283 (K. 189h) – 463 Piano Mozart 2006 Presto Piano Sonata No. 6 in D major, K. 284 (K. 205b) - 464 Piano Mozart 2006 Thema und 12 Variationen Piano Sonata No. 7 in C major, K. 309 (K. 284b) - 465 Piano Mozart 2006 Rondeau, Allegretto grazioso Piano Sonata No. 8 in A minor, K. 310 (K. 300d) - 466 Piano Mozart 2006 Andante cantabile con espressione Piano Sonata No. 8 in A minor, K. 310 (K. 300d) - 467 Piano Mozart 2006 Presto Piano Sonata No. 9 in D major, K. 311 (K. 284c) - 468 Piano Mozart 2006 Rondeau, Allegro Suite for piano in C major (fragment), K. 399 (K. 469 Piano Mozart 2006 385i) Variations for piano in A major on 'Come un agnel- 470 Piano Mozart 2006 lo' K. 460 (K. 454a) Variations for piano in C major on 'Ah, vous dirai-je 471 Piano Mozart 2006 maman' K. 265 (K. 300e) Variations for piano in E flat major on 'Je suis Lin- 472 Piano Mozart 2006 dor' K. 354 (K. 299a) Variations for piano in F major on 'Dieu d'amour' K. 473 Piano Mozart 2006 352 (K. 374c) Variations for piano in F major on 'Ein Weib ist das 474 Piano Mozart 2006 herrlichste Ding' K. 613 Variations for piano in F major on 'Salve tu, 475 Piano Mozart 2006 Domine' K. 398 (K. 416e)

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Variations for piano in G major on Salieri's 'Mio 476 Piano Mozart 2006 caro adone' K. 180 (K. 173c) 477 Piano Scriabin Etudes Op. 8 - A major 2007 478 Piano Scriabin Etudes Op. 8 - A-flat major 2007 479 Piano Scriabin Etudes Op. 8 - B major 2007 480 Piano Scriabin Etudes Op. 8 - B minor 2007 481 Piano Scriabin Etudes Op. 8 - B-flat minor (2nd) 2007 482 Piano Scriabin Etudes Op. 8 - B-flat minor 2007 483 Piano Scriabin Etudes Op. 8 - C sharp minor 2007 484 Piano Scriabin Etudes Op. 8 - D-flat major 2007 485 Piano Scriabin Etudes Op. 8 - D-sharp minor 2007 486 Piano Scriabin Etudes Op. 8 - E major 2007 487 Piano Scriabin Etudes Op. 8 - F sharp minor 2007 488 Piano Scriabin Etudes Op. 8 - G-sharp minor 2007 489 Piano Scriabin Preludes Op. 11 No. 19 - E-flat major - Affettuoso 2007 490 Piano Scriabin Preludes Op. 11 No. 20 - C minor - Appassionato 2007 491 Piano Scriabin Preludes Op. 11 No. 21 - B-flat major - Andante 2007 492 Piano Scriabin Preludes Op. 11 No. 22 - G minor - Lento 2007 493 Piano Scriabin Preludes Op. 15 No. 1 - A major - Andante 2007 494 Piano Scriabin Preludes Op. 15 No. 3 - E major - Allegro assai 2007 495 Piano Scriabin Preludes Op. 15 No. 4 - E major - Andantino 2007 496 Piano Scriabin Preludes Op. 15 No. 5 - C sharp minor - Andante 2007 497 Piano Scriabin Preludes Op. 16 No. 1 – Andante 2007 498 Piano Scriabin Preludes Op. 16 No. 2 – Allegro 2007 499 Piano Scriabin Preludes Op. 16 No. 3 - Andante Cantabile 2007 500 Piano Scriabin Preludes Op. 16 No. 4 – Lento 2007 501 Jazz Art Blakey The most beautiful girl in the world 2013 502 Jazz Art Blakey Moanin' Are You Real 2013 503 Jazz Art Blakey Moanin' Blues March 2013 504 Jazz Art Blakey Moanin' Cry a Blue 2013 505 Jazz Art Blakey Moanin' Moanin' 2013 506 Jazz Art Blakey Moanin' Warm-Up and Dialogue Between Lee and Rudy 2013 Ben Webster + Thelo- nious Monk Trio Art 507 Jazz Have you met miss Jones 2013 Tatum + Thelonious Monk Ben Webster + Thelo- nious Monk Trio Art 508 Jazz Night an Day 2013 Tatum + Thelonious Monk 509 Jazz Cedar Walton Back to Bologna 2001 510 Jazz Cedar Walton Darn That Dream 2001 511 Jazz Cedar Walton I'll Know 2001 512 Jazz Cedar Walton N.P.S 2001 513 Jazz Cedar Walton Promise Land 2001 514 Jazz Cedar Walton Thirty Degrees to the Wind 2001 Clifford Brown & Max 515 Jazz If I Love Again 2013 Roach Giant Steps Clifford Brown & Max 516 Jazz Gerkin For Perkin 2013 Roach Giant Steps Clifford Brown & Max 517 Jazz Jacqui 2013 Roach Giant Steps Clifford Brown & Max 518 Jazz Swingin' 2013 Roach Giant Steps

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Clifford Brown & Max 519 Jazz Take The 'A' Train 2013 Roach Giant Steps 520 Jazz Coleman Hawkins Bird of Prey Blues 2013 521 Jazz Coleman Hawkins Get Set 2013 522 Jazz Coleman Hawkins Hanid 2013 523 Jazz Coleman Hawkins Honey Flower 2013 524 Jazz Coleman Hawkins Nabob 2013 525 Jazz Coleman Hawkins Ooh-Wee Miss G.P.! 2013 526 Jazz Coleman Hawkins Sunday 2013 527 Jazz Coleman Hawkins Vignette 2013 528 Jazz Count Basie Duet 2013 529 Jazz Count Basie Kid from Red Bank 2013 530 Jazz Count Basie Sleepwalker's Serenade 2013 531 Jazz Count Basie Teddy the Toad 2013 532 Jazz Count Basie Whirlybird 2013 Daniel Schenker Quar- 533 Jazz Cascade 2010 tet Daniel Schenker Quar- 534 Jazz Jardim Botanico 2010 tet Daniel Schenker Quar- 535 Jazz KL Blue 2010 tet Daniel Schenker Quar- 536 Jazz Late 2010 tet Daniel Schenker Quar- 537 Jazz Leaving the Post 2010 tet Daniel Schenker Quar- 538 Jazz Nordost 2010 tet Daniel Schenker Quar- 539 Jazz Roseira 2010 tet Daniel Schenker Quar- 540 Jazz Rua Cxunde 2010 tet 541 Jazz Dave Brubeck Audrey 2011 542 Jazz Dave Brubeck Bossa Nova USA 2011 543 Jazz Dave Brubeck Cable Car 2011 544 Jazz Dave Brubeck Everybody's Jumpin' 2011 545 Jazz Dave Brubeck Height-Ho 2011 546 Jazz Dave Brubeck Koto Song 2011 547 Jazz Dave Brubeck My Favorite Things 2011 548 Jazz Dave Brubeck Stompin' For Milli 2011 549 Jazz Dave Brubeck Take Five 2011 550 Jazz Dave Brubeck There'll Be Some Changes Made 2011 551 Jazz Dave Brubeck Unsquare Dance 2011 552 Jazz Ernie Watts Quartet Bass Geige 'Bahss Guy-Geh' 2011 553 Jazz Ernie Watts Quartet Crescent 2011 554 Jazz Ernie Watts Quartet Palmito 2011 555 Jazz Ernie Watts Quartet Twilight Waltz 2011 556 Jazz Ernie Watts Quartet You Are There 2011 John Coltrane Giant 557 Jazz Study In Brown - Giant Steps 2013 Steps John Coltrane Giant 558 Jazz Study In Brown – Spiral 2013 Steps John Coltrane Giant 559 Jazz Study In Brown - Mr. P.C 2013 Steps 560 Jazz Miles Davis A Night in Tunisia 2004

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561 Jazz Miles Davis Ah Leu Cha 2005 562 Jazz Miles Davis Airegin 2004 563 Jazz Miles Davis All Blues 2013 564 Jazz Miles Davis All of You 2005 565 Jazz Miles Davis Budo 2002 566 Jazz Miles Davis Conception 2002 567 Jazz Miles Davis Dear Stockholm 2005 568 Jazz Miles Davis Denial 2002 569 Jazz Miles Davis Diane 2005 570 Jazz Miles Davis Doxy 2004 571 Jazz Miles Davis Flamenco Sketches - Alternate Take 2013 572 Jazz Miles Davis Four 2005 573 Jazz Miles Davis Freddie Freeloader 2013 574 Jazz Miles Davis Half Nelson 2005 575 Jazz Miles Davis I Could Write a Book 2005 576 Jazz Miles Davis I'll Remember April 2004 577 Jazz Miles Davis If I Were a Bell 2005 578 Jazz Miles Davis In Your Own Sweet Way 2005 579 Jazz Miles Davis It Could Happen to You 2005 580 Jazz Miles Davis Made in Heaven -The Story of Kind of Blue 2013 581 Jazz Miles Davis Miles Speaks 2013 582 Jazz Miles Davis Milestones 2002 583 Jazz Miles Davis Moose Themooche 2002 584 Jazz Miles Davis No Line 2005 585 Jazz Miles Davis Oleo 2005 586 Jazz Miles Davis So What 2013 587 Jazz Miles Davis Surrey with the Fringe on Top 2005 588 Jazz Miles Davis Sweet Sue, Just You 2005 589 Jazz Miles Davis The Theme 2004 590 Jazz Miles Davis Trane's Blues 2005 591 Jazz Miles Davis Vierd Blues 2005 592 Jazz Miles Davis Walkin' 2004 593 Jazz Miles Davis When Lights Are Low 2004 594 Jazz Miles Davis Woody 'N' You 2005 595 Jazz Miles Davis Yardbird Suite 2002 596 Jazz Reto Suhner Quartet A band-aid for your complex 2006 597 Jazz Reto Suhner Quartet CS 2006 598 Jazz Reto Suhner Quartet Schwäne im Weltall 2006 599 Jazz Reto Suhner Quartet Waltz 2006 600 Jazz Reto Suhner Quartet Äbä 2006 601 Pop Backstreet Boys Time 2000 602 Pop Backstreet Boys Everyone 2000 603 Pop Backstreet Boys Shape Of My Heart 2000 604 Pop Backstreet Boys Shining Star 2000 605 Pop Backstreet Boys Yes I Will 2000 606 Pop Beyonce Me, Myself And I 2003 607 Pop Beyonce Naughty Girl 2003 608 Pop Blue All Rise 2001 609 Pop Blue Bounce 2001 610 Pop Blue Make It Happen 2001 611 Pop Blue This Temptation 2001 612 Pop Blue Too Close 2001 613 Pop Britney Spears Can't Make You Love Me 2000

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614 Pop Britney Spears Don't Go Knockin' On My Door 2000 615 Pop Britney Spears Oops I Did It Again 2000 616 Pop Britney Spears Stronger 2000 617 Pop Britney Spears Toxic 2003 618 Pop Daniel Bedingfield Girlfriend 2003 619 Pop Dido All You Want 2002 620 Pop Dido Life For Rent 2003 621 Pop Dido Sand In My Shoes 2003 622 Pop Dido Thank You 2001 623 Pop Dido White Flag 2003 624 Pop Enrique Iglesias Heroe 2001 625 Pop Enrique Iglesias I Will Survive 2001 626 Pop Gabrielle Because Of You 2001 627 Pop Gabrielle Dreams 2001 628 Pop Gabrielle Rise 2001 629 Pop Gareth Gates Downtown 2002 630 Pop Hear'Say Can't Stop Thinkin' About It 2001 631 Pop Hear'Say Pure And Simple 2001 632 Pop Herbert Grönemeyer Mensch 2002 633 Pop James Blunt Cry 2005 634 Pop James Blunt High 2004 635 Pop James Blunt Out Of My Mind 2004 636 Pop James Blunt Tears And Rain 2004 637 Pop James Blunt Wisemen 2004 638 Pop James Blunt You're Beautiful 2004 639 Pop Justin Timberlake Last Night 2002 640 Pop Justin Timberlake Like I Love You 2002 641 Pop Justin Timberlake Losing My Way 2006 642 Pop Kyle Minogue More More More 2001 643 Pop Kylie Minogue Your Love 2001 644 Pop Lady Gaga Boys Boys Boys 2008 645 Pop Lady Gaga Eh, Eh (Nothing Else I Can Say) 2008 646 Pop Lady Gaga I Like It Rough 2008 647 Pop Lady Gaga Just Dance 2008 648 Pop Lady Gaga Money Honey 2008 649 Pop Lady Gaga Paparazzi 2008 650 Pop Lady Gaga Paper Gangsta 2008 651 Pop Lady Gaga Poker Face 2008 652 Pop Madonna Forbidden Love 2005 653 Pop Madonna Get Together 2005 654 Pop Madonna Hung Up 2005 655 Pop Madonna I Love New York 2005 656 Pop Madonna Let It Will Be 2005 657 Pop Madonna Like It Or Not 2005 658 Pop Madonna Like It Or Not 2005 659 Pop Madonna Music 2000 660 Pop Madonna Sorry 2005 661 Pop Michael Jackson Billie Jean 2009 662 Pop Michael Jackson Blood On The Dance Floor 2003 663 Pop Michael Jackson Human Nature 2009 664 Pop Michael Jackson Jam 2009 665 Pop Michael Jackson Man In The Mirror 2009 666 Pop Michael Jackson Rock With You 2003

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667 Pop Michael Jackson Smooth Criminal 2009 668 Pop Michael Jackson The Way You Make Me Feel 2009 669 Pop Michael Jackson This Is It (Album Version) 2009 670 Pop Michael Jackson Wanna Be Startin' Somethin' 2009 671 Pop Michael Jackson You Are Not Alone 2003 672 Pop Pussycat Dolls Bite The Dust 2005 673 Pop Pussycat Dolls Buttons 2005 674 Pop Pussycat Dolls Don't Cha 2005 675 Pop Pussycat Dolls Hot Stuff (I Want You Back) 2005 676 Pop Pussycat Dolls I Don't Need A Man 2005 677 Pop Pussycat Dolls Stickwitu 2005 678 Pop Pussycat Dolls Tainted Love_Where Did Our Love Go 2005 679 Pop Robbie Williams Advertising Space 2005 680 Pop Robbie Williams Feel 2002 681 Pop Robbie Williams Ghosts 2005 682 Pop Robbie Williams Make Me Pure 2005 683 Pop Robbie Williams Please Don't Die 2005 684 Pop Robbie Williams Sin Sin Sin 2005 685 Pop Robbie Williams The Trouble With Me 2005 686 Pop Robbie Williams Tripping 2005 687 Pop Ronan Keating Heal Me 2000 688 Pop Ronan Keating If I Don't Tell You Now 2000 689 Pop Ronan Keating If Tomorrow Never Comes 2002 690 Pop Ronan Keating We've Got Tonight 2002 691 Pop Ronan Keating, Yusuf Father and Son 2005 692 Pop S Club 7 Don't Stop Movin' 2001 693 Pop S Club 7 I'll be there 2000 694 Pop Spice Girls Holler 2000 695 Pop Westlife Change Your Mind 2005 696 Pop Westlife Colour My World 2005 697 Pop Westlife Desperado 2005 698 Pop Westlife She's Back 2005 699 Pop Westlife When You Tell Me That You Love Me 2005 700 Pop Westlife You Raise Me Up 2005 701 Rap 50 Cent Life's On The Line 2000 702 Rap 50 Cent Back Down 2003 703 Rap 50 Cent Gotta Make It To Heaven 2003 704 Rap 50 Cent Heat 2003 705 Rap 50 Cent High All The Time 2003 706 Rap 50 Cent If I Can't 2003 707 Rap 50 Cent In Da Club 2003 708 Rap 50 Cent Many Men (Wish Death) 2003 709 Rap 50 Cent P.I.M.P. 2003 710 Rap 50 Cent Poor Lil Rich 2003 711 Rap 50 Cent Wanksta 2003 712 Rap 50 Cent 8 U Not Like Me 2003 713 Rap 50 Cent ft. Eminem Patiently Waiting 2003 714 Rap 50 Cent ft. Tony Yayo Like My Style 2003 715 Rap 50 Cent ft. Young Buck Blood Hound 2003 716 Rap Eminem Till I Collapse 2002 717 Rap Eminem Amityville 2000 718 Rap Eminem Business 2002 719 Rap Eminem Cleanin' Out My Closet 2002

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720 Rap Eminem Criminal 2000 721 Rap Eminem Drug Ballad 2000 722 Rap Eminem I'm Back 2000 723 Rap Eminem Just Lose It 2004 724 Rap Eminem Kill You 2000 725 Rap Eminem Like Toy Soldiers 2004 726 Rap Eminem Lose Yourself 2003 727 Rap Eminem Mockingbird 2004 728 Rap Eminem My Dad's Gone Crazy 2002 729 Rap Eminem Say What You Say 2002 730 Rap Eminem Sing For The Moment 2002 731 Rap Eminem Soldier 2007 732 Rap Eminem Square Dance 2002 733 Rap Eminem The Real Slim Shady 2000 734 Rap Eminem The Way I Am 2000 735 Rap Eminem When The Music Stops 2002 736 Rap Eminem Who Knew 2000 737 Rap Eminem ft Nate Dogg Shake That 2006 738 Rap Eminem ft. D12 Under The Influence 2000 Eminem ft. Sticky Fin- 739 Rap Remember Me 2000 gaz, Eric Collins Eminem ft. Xzibit, 740 Rap Bitch Please 2000 Snoop Dogg Freeway ft. Nelly, 741 Rap Murphy Lee, Beanie Roc The Mic (Remix) 2002 Siegel 742 Rap Jay Z All I Need 2001 743 Rap Jay Z Blueprint (Momma Loves Me) 2001 744 Rap Jay Z Girls, Girls, Girls 2001 745 Rap Jay Z Heart Of The City (Ain't No Love) 2001 746 Rap Jay Z Hola' Hovito 2001 747 Rap Jay Z Izzo (H.O.V.A.) 2001 748 Rap Jay Z Jigga That Nigga 2001 749 Rap Jay Z Never Change 2001 750 Rap Jay Z Song Cry 2001 751 Rap Jay Z Takeover 2001 752 Rap Jay Z The Ruler's Back 2001 753 Rap Jay Z U Don't Know 2001 754 Rap Jay Z ft. Eminem Renegade 2001 755 Rap Jay Z, Kanye West Otis 2011 756 Rap Kanye West Barry Bonds 2007 757 Rap Kanye West Big Brother 2007 758 Rap Kanye West Champion 2007 759 Rap Kanye West Crack Music 2005 760 Rap Kanye West Dark Fantasy 2010 761 Rap Kanye West Drive Slow 2005 762 Rap Kanye West Everything I Am 2007 763 Rap Kanye West Flashing Lights 2007 764 Rap Kanye West Gold Digger 2005 765 Rap Kanye West Gone 2005 766 Rap Kanye West Good Life 2007 767 Rap Kanye West Good Morning 2007 768 Rap Kanye West Heard 'Em Say 2005 769 Rap Kanye West Hell Of A Life 2010

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770 Rap Kanye West Homecoming 2007 771 Rap Kanye West I Wonder 2007 772 Rap Kanye West My Way Home 2005 773 Rap Kanye West So Appalled 2010 774 Rap Kanye West Stronger 2007 775 Rap Kanye West Touch The Sky 2005 Kanye West ft Jay Z 776 Rap Nicki Minaj, Bon Iver, Monster 2010 Rick Ross 777 Rap Nelly #1 2002 778 Rap Nelly Air Force Ones 2002 779 Rap Nelly Cg 2 2002 780 Rap Nelly Dem Boyz 2002 781 Rap Nelly Oh Nelly 2002 782 Rap Nelly Say Now 2002 783 Rap Nelly ft. King Jacob On The Grind 2002 784 Rap OutKast Bowtie 2003 785 Rap OutKast Church 2003 786 Rap OutKast Flip Flop Rock 2003 787 Rap OutKast Ghetto Musick 2003 788 Rap OutKast Knowing 2003 789 Rap OutKast Last Call 2003 790 Rap OutKast Reset 2003 791 Rap OutKast The Rooster 2003 792 Rap OutKast Tomb Of The Boom 2003 793 Rap OutKast Unhappy 2003 794 Rap OutKast War 2003 795 Rap The Black Eyed Peas Anxiety 2003 796 Rap The Black Eyed Peas Hey Mama 2003 797 Rap The Black Eyed Peas Latin Girls 2003 798 Rap The Black Eyed Peas Sexy 2003 799 Rap The Black Eyed Peas Smells Like Funk 2003 800 Rap The Blacked Eyed Peas Hands Up 2003 801 Rock Arctic Monkeys The View From The Afternoon 2006 802 Rock Arctic Monkeys From The Ritz To The Rubble 2006 803 Rock Arctic Monkeys Teddy Picker 2007 804 Rock Arctic Monkeys The Bad Thing 2007 805 Rock Arctic Monkeys This House Is A Circus 2007 806 Rock Band of Horses The Great Salt Lake 2006 807 Rock Band of Horses Weed Party 2006 808 Rock Band of Horses Wicked Gil 2006 809 Rock Blank 182 First Date 2001 810 Rock Blink 182 Anthem Part Two 2001 811 Rock Blink 182 Online Songs 2001 812 Rock Blink 182 Shut Up 2001 813 Rock Blink 182 Story Of A Lonely Guy 2001 814 Rock Blink 182 The Rock Show 2001 815 Rock Bloc Party Banquet 2005 816 Rock Bloc Party Helicopter 2005 817 Rock Bloc Party Luno 2011 818 Rock Bloc Party Song For Clay (Disappear Here) 2007 819 Rock Brand New Millstone 2006 820 Rock Brand New Not The Sun 2006

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821 Rock Brand New Sowing Season 2006 822 Rock Brand New You Won't Know 2006 823 Rock Bruce Springsteen Further On (Up The Road) 2002 824 Rock Bruce Springsteen Lonesome Day 2002 825 Rock Bruce Springsteen The Fuse 2002 826 Rock Bruce Springsteen Worlds Apart 2002 827 Rock Death Cab For Cutie Long Division 2008 828 Rock Editors Bullets (Single Version) 2005 829 Rock Editors Heads In Bags 2005 830 Rock Foo Fighters Bridge Burning 2011 831 Rock Foo Fighters Overdrive 2002 832 Rock Foo Fighters The Pretender 2007 833 Rock Foo Fighters These Days 2011 834 Rock Foo Fighters Times Like These 2002 835 Rock Foo Fighters Walk 2011 836 Rock Franz Ferdinand Do You Want To 2005 837 Rock Franz Ferdinand This Boy 2005 838 Rock Franz Ferdinand Well That Was Easy 2005 839 Rock Franz Ferdinand You Could Have It So Much Better 2005 840 Rock Franz Ferdinand You're The Reason I'm Leaving 2005 841 Rock Green Day 21 Guns 2009 842 Rock Green Day 21st Century Breakdown 2009 843 Rock Green Day American Idiot 2004 844 Rock Green Day Boulevard Of Broken Dreams 2004 845 Rock Green Day Jesus Of Suburbia 2004 846 Rock Green Day Know Your Enemy 2009 847 Rock Green Day Wake Me Up When September Ends 2004 848 Rock Guns'N'Roses Knockin' On Heaven's Door 2004 849 Rock Guns'N'Roses Welcome To The Jungle 2004 850 Rock Jimmy Eat World Futures 2004 851 Rock Jimmy Eat World Kill 2004 852 Rock Jimmy Eat World Nothingwrong 2004 853 Rock Jimmy Eat World Pain 2004 854 Rock Jimmy Eat World The World You Love 2004 855 Rock Manic Street Preachers Jackie Collins Existential Question Time 2009 856 Rock Manic Street Preachers Journal For Plague Lovers 2009 857 Rock Manic Street Preachers Marlon J.D. 2009 858 Rock Manic Street Preachers Me And Stephen Hawking 2009 859 Rock Manic Street Preachers Peeled Apples 2009 860 Rock Manic Street Preachers Virginia State Epileptic Colony 2009 861 Rock Muse Hyper Music 2001 862 Rock Muse Uprising 2009 863 Rock Oasis Ain't Got Nothin' 2008 864 Rock Oasis Bag It Up 2008 865 Rock Oasis The Nature Of Reality 2008 866 Rock Oasis The Shock Of The Lightning 2008 867 Rock Oasis The Turning 2008 868 Rock Oasis Waiting For The Rapture 2008 869 Rock Phoenix 1901 2009 870 Rock Porcupine Tree Deadwing 2005 871 Rock Porcupine Tree Open Car 2005 872 Rock Porcupine Tree Shallow 2005 873 Rock Queens of the Stone Go With The Flow 2002

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Age Queens of the Stone 874 Rock Gonna Leave You 2002 Age Queens of the Stone 875 Rock Hangin' Tree 2002 Age Queens of the Stone 876 Rock No One Knows 2002 Age Queens of the Stone You Think I Ain't Worth A Dollar But I Feel Like A 877 Rock 2002 Age Millionaire 878 Rock Silversun Pickups Lazy Eye 2006 879 Rock Snow Patrol Hands Open 2006 880 Rock Snow Patrol Headlights On Dark Roads 2006 881 Rock Snow Patrol You're All I Have 2006 882 Rock Super Furry Animals (Drawing) Rings Around The World 2001 883 Rock The Beatles Come Together 2000 884 Rock The Beatles Day Tripper 2000 885 Rock The Beatles Get Back 2000 886 Rock The Killers For Reasons Unknown 2006 887 Rock The Killers Jenny Was A Friend Of Mine 2004 888 Rock The Killers Mr. Brightside 2004 889 Rock The Killers On Top 2004 890 Rock The Killers Sam's Town 2006 891 Rock The Killers Smile Like You Mean It 2004 892 Rock The Vaccines If You Wanna 2011 893 Rock The Vaccines All In White 2011 894 Rock The Vaccines Post Break-Up Sex 2011 895 Rock The Vaccines Wolf Pack 2011 896 Rock The Vaccines Wreckin' Bar (Ra Ra Ra) 2011 897 Rock U2 All Because Of You 2004 898 Rock U2 Elevation 2000 899 Rock U2 Vertigo 2004 900 Rock Yeah Yeah Yeah Dull Life 2009 901 Schlager ANDREA Vielleicht war alles nur geträumt 2011 902 Schlager Alexander Klaws Morgen explodiert die Welt 2014 903 Schlager Andre Stade Kein Wort bricht das Schweigen 2011 904 Schlager Andrea Berg Der letzte Tag im Paradies 2014 905 Schlager Andreas Martin Für dich 2014 906 Schlager Andy Borg Adios Amor 2001 907 Schlager Andy Borg Arrivederci Claire 2001 908 Schlager Bata Illic Michaela 2001 909 Schlager Beatrice Egli Auf die Plätze, fertig, ins Glück! 2011 910 Schlager Beatrice Egli Verrückt nach dir 2014 911 Schlager Bernd Clüver Mexican Girl 2001 912 Schlager Bernhard Brink Aus dem Leben gegriffen 2014 913 Schlager Bernhard Brink Die Liebe 2011 914 Schlager Bill Ramsey Pigalle 2001 915 Schlager Brings Kölsche Jungs 2014 Hab' Ich Dir Heute Schon Gesagt, Dass Ich Dich 916 Schlager Chris Roberts 2001 Liebe 917 Schlager Chris Roberts Ich Bin Verliebt in Die Liebe 2001 918 Schlager Christian Franke Doch schweigen werd ich nicht 2011 919 Schlager Christian Lais Wer kämpft neben mir 2014 920 Schlager Christian Stark Überflieger 2011 921 Schlager Claudio Diamanten & Perlen 2011

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922 Schlager Conny Engel Ich glaub an Engel 2011 923 Schlager Daliah Lavi Oh, Wann Kommst Du 2001 924 Schlager Daniela Alfinito Wenn der Wahnsinn zu Ende ist 2011 925 Schlager Diana Sorbello Ti Sento 2011 926 Schlager Die Cappuccinos Raphaela Remix 2014 927 Schlager Ella Endlich Wär ich ein Buch 2011 928 Schlager Fantasy Darling 2014 929 Schlager Fantasy Jetzt liebt er sie 2011 930 Schlager Feller & Feller Mal sind die Wolken grau und schwer 2011 931 Schlager Frank Farian Rocky 2001 932 Schlager Franziska Polarstern 2014 933 Schlager Freudenberg & Lais Du bist meine Burg 2014 934 Schlager G.G. Anderson So nah am Paradies 2011 935 Schlager Gilbert Durchgebrannt 2014 936 Schlager Gitte Henning Mit jedem Abschied fängt was an 2011 937 Schlager Heike Schäfer Schöne Bambol 2011 938 Schlager Helene Fischer Atemlos durch die Nacht 2014 939 Schlager Hoffmann & Hoffmann Himbeereis zum Frühstück 2001 940 Schlager Howard Carpendale In diesem Moment 2014 941 Schlager Höhner Steh auf, mach laut! 2014 942 Schlager Ibo Ibiza 2001 943 Schlager Ireen Sheer Heut' Abend Hab' Ich Kopfweh 2001 944 Schlager Ireen Sheer Jeden Tag 2011 945 Schlager Jan Smit Noch einmal mein Herz 2014 946 Schlager Jörg Bausch Trau dich, nimm mich 2011 947 Schlager Jürgen Drews Und wir waren wie Vampire 2014 948 Schlager Kristina Bach Dein Vielleicht hat nicht gereicht 2014 949 Schlager Larissa Strogoff Der große Traum 2011 950 Schlager Laura Wilde Ich sehe was, was du nicht siehst 2011 951 Schlager Leonard Sternenfänger 2011 952 Schlager Licht Näher zu Dir 2011 953 Schlager Linda Hesse Knutschen... ich kann nichts dafür 2014 954 Schlager Linda Hesse Verbotene Liebe 2014 955 Schlager Lindt Bennett Guten Tag ich bin dein Leben 2014 956 Schlager Marco Kloss Ein Diamant 2011 957 Schlager Markus Ich bin nicht Spiderman 2014 958 Schlager Matthias Reim 1000 Mal 2014 959 Schlager Matthias Stingl Lust auf tausend kleine Dinge 2011 960 Schlager Michael Holm Barfuss im Regen 2001 961 Schlager Michael Holm St. Pauli Shuffle 2011 962 Schlager Michael Kern Maria Elena (1, 2 wieder einer weg) 2011 963 Schlager Michael Morgan Für immer nur du 2014 964 Schlager Michelle Herzstillstand 2014 965 Schlager Michelle Paris 2014 966 Schlager Monika Martin Mein Engel bist du 2011 967 Schlager Nicole Ein neuer Tag 2014 968 Schlager Nicole Mit Leib und Seele 2011 969 Schlager Nik P Was wär 2011 970 Schlager Nik P. Du musst ein Engel sein 2014 971 Schlager Nik P. Geboren um dich zu lieben 2014 972 Schlager Nockalm Quintett Du warst der geilste Fehler meines Lebens 2011 973 Schlager Norman Langen Ich wähl deine Nummer 2014 974 Schlager Oliver Maria Lenzi David und Goliath 2011

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975 Schlager Patrick Lindner Das verlorene Lächeln 2011 976 Schlager Peter Cornelius Du Entschuldige I Kenn Di 2001 977 Schlager Peter Kraus Lila Wolken 2014 978 Schlager Peter Rubin Tränen der Liebe 2011 979 Schlager Playa Rouge Warts´s ab 2011 980 Schlager Raffaele Hitmix 2011 981 Schlager Rendezvous Dein allergrößter Traum 2011 982 Schlager Rex Gildo Fiesta Mexicana 2001 Roland Kaiser & Maite 983 Schlager Warum hast du nicht nein gesagt 2014 Kelly 984 Schlager Roland Kaiser Sieben Fässer Wein 2001 985 Schlager Ronny Krappmann Kalt wie Eis 2011 986 Schlager Rudi Carrell Wann Wird's Mal Wieder Richtig Sommer 2001 987 Schlager Santiano Hoch im Norden 2014 988 Schlager Semino Rossi Dich zu lieben ist schön 2014 989 Schlager Simone Sehnsucht kommt nicht von ungefähr 2011 990 Schlager Siw Malmkvist Liebeskummer Lohnt Sich Nicht 2001 991 Schlager Susan Ebrahimi Ballerina 2011 992 Schlager Sylvia Martens Kleine Schönheitsfehler 2011 993 Schlager Tommy Steiner Wo sind unsere wilden Jahre 2011 994 Schlager Udo Jürgens Der Mann ist das Problem 2014 995 Schlager Ulli Martin Ich Träume mit Offenen Augen von Dir 2001 996 Schlager Ute Freudenberg Begegnen 2014 997 Schlager Uwe Busse Applaus für dich 2014 998 Schlager Vicky Leandros Doch ich seh all die Rosen 2011 999 Schlager Vicky Leandros Theo, Wir Fahr'n Nach Lodz 2001 1000 Schlager Wencke Myhre Beiss nicht Gleich in Jeden Apfel 2001

134 Chapter 5: Harmonic Frequency Lowering

Chapter 5 Harmonic Frequency Lower- ing: Effects on the Perception of Music De- tail and Sound Quality

The content in this chapter was published in the journal Trends in Hearing .

Impact Factor: 1.92

Authors: Martin Kirchberger and Frank Russo

Kirchberger, M., & Russo, F. A. (2016). Harmonic Frequency Lowering: Effects on the Perception of Music Detail and Sound Quality. Trends in Hearing , 20 , DOI: 10.1177/2331216515626131.

135 Chapter 5: Harmonic Frequency Lowering

Abstract

A novel algorithm for frequency lowering in music was developed and experimentally tested in hearing-impaired listeners. Harmonic frequency lowering (HFL) combines frequency transposition and frequency compression to preserve the harmonic content of music stimuli. Listeners were asked to make judgments regarding detail and sound quality in music stimuli. Stimuli were presented under different signal-processing conditions: original, low-pass filtered, HFL, and nonlinear frequency-compressed. Results showed that participants reported perceiving the most detail in the HFL condition. In addition, there was no difference in sound quality across conditions.

5.1 Introduction Frequency lowering is one strategy to increase the audibility of acoustic signals for the hearing- impaired listener. Higher frequencies that are inaudible for the hearing-impaired listener are mapped towards lower frequencies. Frequency lowering can be achieved by frequency transposition (FT) and frequency compression (FC) (Kuk et al. 2009). In frequency transposition, the high- frequency components of the spectrum are shifted lower and mixed with the original signal. In frequency compression, the high-frequency portion of the spectrum is compressed to fit into a narrower target bandwidth and there is no spectral superimposition of the original and the compressed signal. The mapping curve can be linear or nonlinear. Linear frequency compression (LFC) maps all input and output frequencies according to Equation 5:1

= ∗

Equation 5:1 – Input-output function for linear frequeny compression.

In nonlinear frequency compression (NFC), the mapping between the input and output frequencies can be described by Equation 5:2 for frequencies above a cut-off .

/ = ∗

Equation 5:2 – Input-output function for nonlinear frequeny compression; constant hereinafter referred to as CR nfc (compression ratio for nonlinear frequency compression).

136 Chapter 5: Harmonic Frequency Lowering

Typically, the low-frequency components remain unmodified in NFC. Figure 5:1 shows examples of the input-output functions for FT, LFC, and NFC strategies.

Frequency-lowering technology currently transposition (FT) exists in the hearing aids of many hear- fout kHz 6 ing-aid manufacturers (McDermott & Knight 2001; Kuk et al. 2006; Baldwin, & 4 Nyfeller 2010; Galster et al. 2011; Kuriger & Lesimple 2012; McDermott, Serman, 2 Hannemann, & Kornagel 2013; Stender & Groth 2014). The hearing aids feature FT,

2 4 6 8 LFC, and NFC strategies and the parame- f kHz in terization can be individually adjusted to linear compression (LFC) the hearing-impaired listener. Depending

fout on the manufacturer, the activity of the 4 kHz lowering schemes is either fixed or

2 adapts to the input signal so that frequency-lowering is only active when relevant acoustic features have been identi-

2 4 6 8 fied.

fin kHz The primary purpose of frequency lower- nonlinear compression (NFC) ing in hearing aids is to increase speech fout 4 intelligibility. Frequency lowering also has kHz a positive side-effect on feedback cancel- 2 ling as a result of decorrelating the input and the output signal (Joson et al. 1993). Consequently, frequency lowering has 2 4 6 8 become an integral feature of hearing-aid fin kHz signal processing. This feature, however, Figure 5:1 Examples of the input-output mapping functions for the different frequency lowering schemes frequency has not been adapted or optimized for transposition (FT), linear frequency compression (LFC), and nonlinear frequency compression (NFC). (FT: cut-off fr e- music. quency 5 kHz, peak frequency: 6 kHz, frequency shift 3 kHz; LFC: compression ratio 3:2; NFC: cut-off frequency 2 kHz, compression ratio CR nfc : 1.7.

137 Chapter 5: Harmonic Frequency Lowering

5.1.1 Benefit of frequency lowering on speech intelligibility The vast majority of studies show that NFC benefits speech intelligibility in hearing-impaired listeners, especially in the perception of fricatives and affricatives (Simpson, Hersbach, & McDermott 2005, 2006; Nyffeler 2008; Glista et al. 2009; Bohnert, Nyffeler, & Keilmann 2010; Wolfe et al. 2010, 2011; Alexander 2012; Glista, Scollie, & Sulkers 2012; Ellis 2012; Kopun et al. 2012; McCreery et al. 2013, 2014; Souza et al. 2013; Stender & Groth 2014; Alnahwi & AlQudehy 2015; Marchesin & Iorio 2015).

Evidence for effects of LFC on speech intelligibility is limited. Those studies that have been completed have small sample sizes and hard-to-interpret findings. Parent, Chmiel, and Jerger (1998) measured a significant improvement for speech understanding in two out of four participants. McDer- mott et al. (1999) obtained evidence for minimal improvement with LFC but noted that the low- frequency electro-acoustic characteristics may have been responsible for these improvements rather than frequency lowering. In a later study, McDermott and Knight (2001) did not find differences in the recognition of monosyllabic words and consonants in the LFC condition but found significant decreases in understanding of sentences in noise.

Studies on FRED (Velmans & Marcuson 1983; Rees & Velmans 1993), an early FT implementation, revealed a clear benefit for discrimination of consonants. Subsequent studies have corroborated benefits of FT for speech intelligibility (Robinson, Baer, & Moore 2007; Auriemmo et al. 2009; Kuk et al. 2009; Smith, Dann, & Brown 2009; Gou et al. 2011). However, other studies have found no effect on speech intelligibility (Robinson et al. 2009) or even a detrimental effect (Alexander, Kopun, & Stelmachowicz 2014).

Differences in outcomes with FL may not only be attributed to the FL strategy but also to the sample size and to the participants’ degree of hearing loss.

5.1.2 Effect of frequency lowering on sound quality of speech and music Regarding the effects of frequency lowering on sound quality of speech, the clinical evidence is scarce and limited to studies involving NFC. Souza et al. (2013) measured a decrease in speech quality for the NFC condition. Parsa et al. (2013) found that hearing-impaired listeners were less sensitive than normal-hearing listeners to quality differences between conventional amplification and

138 Chapter 5: Harmonic Frequency Lowering different NFC parameterizations. In general, sound quality was lower in NFC, and the cut-off parameter effected quality judgments more than the compression ratio. Brennan et al. (2014) revealed that preference of NFC over conventional amplification was dependent on bandwidth. Participants preferred NFC over conventional amplification if the bandwidth of the conventionally amplified signal was limited to the bandwidth of the NFC signal (i.e., around 5 ). However, when the bandwidth of the conventionally amplified signal was not limited (i.e., 11 ), no preference for NFC was observed.

Research on the effects of frequency lowering on music is also lacking. Uys et al. (2012) found that NFC led to improvements in reverberance, tininess, and overall fidelity. Parsa et al. (2013) found that while normal-hearing individuals had a preference for conventional amplification over NFC with music signals, the same preference was non-existent in hearing-impaired listeners. Brennan et al. (2014) reported that the degree of high-frequency loss affected preference ratings. Participants with greater high-frequency hearing loss are more likely to prefer NFC, while participants with less high-frequency hearing loss are more likely to prefer non-compressed versions with full bandwidth. All in all, the state-of-the-art frequency-lowering technologies show a general benefit for speech intelligibility but not necessarily for sound quality of speech or music.

FT and NFC represent threats to the sound quality of the music signal as they can compromise the integrity of the harmonic structure. The transposed or compressed components of the lowered signal are almost never in harmony with the original signal or low-frequency content respectively. Figure 5:2 shows the spectrum of a consonant tone dyad of two complex tones with fundamental frequencies at = 800 and = 2000 (ratio 2:5) and harmonics until 8 in an original version, processed with NFC, and processed with FT. In the example, the cut-off frequency for the NFC condition was set to 2 ; the frequency shift for the FT condition was determined by half the peak frequency 6 ÷ 2 = 3 with a corresponding source region between 4 and 8 . In the NFC condition, all harmonics above 2 are inharmonically distorted. Also in the FT condition, the transposition creates inharmonic components to the complex tone dyad at 1, 1.8, 2.6, 3, 3.4, and 4.2 .

139 Chapter 5: Harmonic Frequency Lowering

8 8 fout fout 7 7 6 6 5 5 4 4 3 3 2 2 kHz 1 1 kHz 0 0 Original NFC FT HFL

Figure 5:2 Spectrum of a tone dyad of two complex tones with fundamental frequencies at 800 Hz (black) and 2000 Hz (blue). The cut-off frequency for the nonlinear frequency compression (NFC) condition was set to 2 kHz and the frequency shift for the frequency transposition (FT) condition was determined at 3 kHz, half the peak frequency at 6 kHz. The cut-off frequency for harmonic frequency lowering (HFL) was set at 4 kHz. New components to the original version after frequency lowering are marked in green.

The frequency mapping function of LFC preserves the harmonic structure. However, as there is no cut-off frequency, LFC is also active in mid and lower frequency regions that are less likely to be affected by hearing loss or for which audibility could easily be restored through conventional amplification.

Pitch perception is manipulated by LFC. A compression ratio of 1.5:1 for example would lower the pitch by a fifth. FT and NFC can also affect pitch perception. If components of a harmonic complex are mistuned, they give rise to a shift in pitch of the whole complex (Moore, Glasberg, & Peters 1985; Meddis and O’Mard 1997). It is widely agreed that the lower harmonics contribute most to this effect (Plomp 1964, 1967; Moore, Glasberg, & Peters 1985; Moore and Gockel 2011). Dai (2000) suggested that the most dominant harmonics are in the frequency region of 600 . The manipulated frequency regions of FT and NFC are usually higher and therefore do not dominate the pitch perception. Nevertheless, they can still have an effect. Moore, Glasberg, and Peters (1985) have shown that a mistuning of the lowest six harmonics of a complex tone with a fundamental frequen-

140 Chapter 5: Harmonic Frequency Lowering cy of 400 has a noticeable effect on pitch perception. The 4th , 5 th , and 6 th harmonic in this example reach frequencies from 1600 to 2400 which are well within the target region of commercial NFC and FT implementations. In sum, FT, NFC, and LFC may not be optimal for preserving sound quality in music. The purpose of this study was to test a frequency-lowering algorithm for music that may address audibility without compromising sound quality. Testing of the algorithm was achieved by asking listeners to judge the perceived detail and quality of music presented under original, low-pass filtered, HFC, and NFC conditions.

5.2 Description of harmonic frequency-lowering algorithm The harmonic frequency-lowering (HFL) algorithm was developed for music and combines frequency compression and frequency transposition to preserve pitch chroma and harmonic structure in music. The algorithm contains three core elements:

(1) A cut-off frequency separates the low-frequency content from the high-frequency content. (2) The high-frequency content is lowered by an octave (i.e., compressed by a linear factor of 2). (3) The compressed frequency content is weighted and then mixed with the original signal.

In general, a harmonic complex tone with a fundamental frequency Fo evokes a pitch perception which corresponds to Fo even if there is no energy present at Fo (Seebeck 1841; Plack & Oxenham 2005). Rather than organizing pitch on a one-dimensional scale from low to high, it is commonly described as a two-dimensional construct inclusive of pitch chroma (class) and pitch height (Stumpf 1890; Drobisch 1852; Meyer 1904; Révész 1913; Bachem 1937, 1950; Deutsch, Dooley, & Henthorn 2008). Pitch chroma refers to the position of the pitch within the octave and pitch height refers to the octave in which it is placed. The octave is the most consonant interval (Schellenberg & Trehub 1994), and many listeners fail to recognize octave transpositions of isolated tones (Cross & Deliege, 2004). Correspondingly, the perception of pitch height can be ambiguous depending on the context (Shepard 1964). A linear compression factor of 2 lowers the high-frequency components by an octave. The lowered components and the original source share the same pitch chroma. The superposition of both signals in HFL therefore preserves the perception of pitch chroma. Harmonic frequency lowering protects the harmonic structure and reduces a potentially negative effect of frequency lowering on tonal consonance. An interference of just-noncoinciding harmonics

141 Chapter 5: Harmonic Frequency Lowering gives rise to the perception of beats or roughness (Vos 1982; Helmholtz & Ellis 2009). For pairs of sinusoids, the beating interactions are most prominent for frequency differences around 3 to 4 (Riesz 1928; Ebel 1952; Zwicker 1952; Terhardt 1974). The linear compression ratio 2:1 results in an alignment of original and lowered harmonics. The lowered even harmonics coincide with the harmonics of the original signal. The odd harmonics are mapped in the middle between two original harmonics. The distance of two adjacent harmonics in the overlapping region of the sum signal is therefore half the fundamental frequency Fo. These frequencies contribute to the perception of a residual / virtual pitch that is one octave lower (Schouten 1938; Schouten, Ritsma, & Cardozo 1962) rather than to tonal dissonance. Figure 5:2 shows the spectrum of a tone dyad when processed with HFL. Compared to the original, new frequency components are created at 2.8 , 3 , and 3.6 . This HFL tone complex can also be regarded as the original complex tone dyad with residual fundamentals at 400 and 1 (ratio 2:5), which share the same chroma as the original dyad and therefore blend well. The linear 2:1 ratio also results in a more aggressive lowering of high-frequency content without adding distortion. An 8 sinusoidal tone is lowered by 4 , which is a more substantial lowering than that which is achieved in standard fittings of commercially available hearing aids. This advantage applies to all frequencies in the lowered bandwidth. Participants with sloping hearing loss and/or dead regions might especially benefit from this attribute. A stronger shift to lower frequencies makes it easier to restore audibility with hearing aids and helps to circumvent dead regions which are more prevalent in the higher frequencies (Pepler et al. 2014).

5.3 Materials and Method

5.3.1 Participants Nineteen hearing-impaired listeners (ages 55-80 yrs, M = 71) were recruited from the internal database of Phonak AG headquarters, Stäfa, Switzerland. Only participants with high-frequency hearing loss who had not yet experienced frequency-lowering signal processing were included. All audiometric data was assessed within one month of the first test date. Table 5:1 contains air conduction thresholds, gender, age, hearing aid, hearing-aid experience, music experience, and the individual parameters used for the NFC algorithm (cut-off frequency and compression ratio, c.f. 5.3.2 Stimuli) for all participants. Music experience was determined according to Kirchberger and Russo (2015).

142 Chapter 5: Harmonic Frequency Lowering

c f n 2 NFC 2 2.1 .8 2.4 2.5 4.5 2.7 0 1 3.4 2.2 0 1.5 3.8 2.4 1 2.5 3.4 2.2 8 0 3.5 2.2 for the NFC (nonlinear nfc 1 12 -2 3.5 2.3 ve 21 1.5 3.1 2 ro 12 0 3.1 2.1 700 6 -2.5 3 2 9 50 -3 3 2 22D 16 -2.5 3.2 2.1 Live 5 0.5 3.3 2.1 o V50 o 0.2 -2 3 2 a 211 a 8.5 -1 3.6 2.3 re500 12 -1.5 2.8 1.9 udiometric udiometric data (dB HL), age (yrs), CAFS 45 -2.5 2.7 1.8 ompression ompression algorithm: a requency requency / Fc, and compression ratio / CR

0.5 1 2 4 6 8 SEX AGE HA HAE ME Fc CR individual individual parameters for the nonlinear frequency c 0.125 0.25 ience ience / ME (scale min: -3, scale max: 4), cut-off f aring was tested. not threshold that 0.5 1 2 4 6 8 Leftear, frequency (kHz) ear, frequency Right (kHz) : : Characteristics of the test participants and the 1 : 5 0.125 0.25 Table Table hearing aid experience / HAE (yrs), and music exper condition.a he NT compression) indicates frequency P1P2 30 30P3 20 35 10P4 60 10 60 5 10P5 70 20 5 5 115P6 65 10 40 105 25 75 20 45P7 45 30 25 55 85 45 60 40 35P8 100 65 65 10 85 35 40 70 70 25 20P9 100 75 45 15 80 80 20 55 75 60 15 15 10 100 70 90 20 75 70 10 25 105 75 15 80 105 5 15 10 50 90 85 40 10 55 10 5 35 15 80 95 70 55 15 75 30 35 20 m 100 90 90 30 90 45 40 30 100 80 95 75 90 50 10 35 90 100 105 70 60 10 45 15 m f 95 80 90 20 65 15Acto Oticon 72 50 80 20 10 75 64 80 65 25 10 m 75 85 1 Azure 95 Resound 70 10 m m 100 74 85 45 >1 Oticon 100 100 67 7322 Savia 40 Phonak m 105 100Savi 100 Phonak m115 PA 72 Widex 100 7 m 70Pure Siemens >1 -1.5Aude Phonak 70 3 Widex 10 -3 3. P10P11 25 30P12 15 55 30P13 70 40 55 75 50P14 75 25 75 50 75 40P15 65 80 20 80 65 90 30 85P16 90 85 50 95 35 >110 75 25 55 90 105P17 35 15 75 25 60 50 40 105 15 35P18 >120 35 80 40 60 45 10 40 50 75 50 30P19 50 55 70 45 30 70 75 55 40 65 60 50 30 65 70 80 95 45 10 75 65 65 65 105 75 85 105 60 30 >110 85 80 >110 90 5 95 90 100 30 50 75 m 80 10 100 95 >115 75 35 50 m 85 85 45 40 78 45 15 90 m 20 65 90 65 121 40 45 10 25 80 73 85 m 65 75 10 105 40 Widex Verso Resound 75 15Extra 85 40 25 Phonak 85 69 105 55 55 25 80 110 65 80 35 5 m mM4- Widex 40 80 10 NT 69 70 55 10 85 95 80 15Pu m m Siemens 65 90Agil Oticon 71 76 80 90 90Resound GN mAlta P Oticon 9 75 75 - fLi Resound GN 55 Oticon 7 -2 3.3 2.

143 Chapter 5: Harmonic Frequency Lowering

5.3.2 Stimuli There were four music segments (S1-S4) selected as source material for test stimuli. The segments contained substantial high-frequency content and spanned a range of genres. The first was a 12.8-s segment from the pop song “Hey Jude” by the Beatles. It included piano, vocals, rhythm guitar, bass guitar, and a tambourine. The second was a 10.5-s segment from the jazz song “The Golden Striker” by Ron Carter. It included piano, double bass, drums (hi-hat), and vibraphone. The third was a 9.6-s segment from the latin song “Mas que nada” by Sergio Mendes featuring Black Eyed Peas. It included vocals, piano, bass, and percussion (cymbals, woodblock, and claps). The fourth was a 10.5-s segment from the dance song “Touch” by Daft Punk. It included strings, bass, synthesizer, and drums (bass, snare, and cymbals).

All songs were retrieved as stereo files with 20480-Hz sampling rate and 16-bit resolution. Segments were selected in a manner that preserved musical phrasing (i.e., did not span phrase boundaries). Stimuli were played back via two loudspeakers at 1.5-m distance forming a stereo triangle with the participant.

For the main experiment, five versions of each segment were individually prepared: Original, NFC, HFL with an individual cut-off frequency (HFLi ), HFL with a default cut-off frequency (HFLo ), and a low-pass filtered version (LP). All files were processed offline to eliminate potential delays. The compression parameters of NFC (i.e., cut-off frequency and compression ratio, Table 5:1) were individually fitted according to the recommendation of the Target TM fitting software. In the HLFi condition, the cut-off frequency was defined as twice the cut-off frequency from the NFC setting. As a result of this definition, the bandwidth of the lower unmodified part of the signal in the HFLi condition equaled the bandwidth of the lower unmodified part of the signal in the NFC condition. Furthermore, the HFLi signal was low-pass filtered to match the total bandwidth of the NFC signal. As there was a spectral overlap of the original signal and the frequency-compressed components, the frequency-compressed component was amplified to be adjusted in level. The gain for the level of the frequency-compressed component in the HFLi signal was determined in a pretest (c.f. page 146, PRETEST).

The only difference between HFLi and HFLo is that for HFLo, the cut-off frequency was fixed at 4 rather than being determined according to the hearing loss of the individual participants. Octave lowering in both HLFo and HLFi was implemented using the pitch-shift plugin SoundShifter from Waves (2013).

144 Chapter 5: Harmonic Frequency Lowering

The LP condition was generated by reducing the bandwidth of the original signal to the bandwidth of the frequency-lowered conditions (NFC and HFL).

Figure 5:3 depicts examples of input-output functions for all five conditions. Figure 5:4 shows an example of how the spectrum of the HFLo condition differs from the spectrum in the LP condition due to the addition of the lowered content.

Original LP fout fout (kHz) (kHz) 6 6

4 4

2 2

2 4 6 8 10 2 4 6 8 10 fin (kHz) fin (kHz) HFL NFC fout fout (kHz) (kHz)

4 4

2 2

fc f 2 4 6 8 10 2c 4 6 8 10 fin (kHz) fin (kHz)

Figure 5:3 Schematic of the different input-output functions that were evaluated in the main test.

5.3.3 Procedures Participants were invited to two separate sessions. In the first session, the pretest was conducted along with the main tests for music detail and sound quality. The participants’ existing hearing aids were also tested to verify the absence of frequency lowering. In the second session, both main tests were repeated and participants filled out the music questionnaire as in Kirchberger and Russo (2015).

145 Chapter 5: Harmonic Frequency Lowering

PRETEST The pretest served as a fitting procedure for the HFL conditions. The lowered portion of the signal and the original signal had overlapping frequency content. Using a virtual slider, participants were asked to adjust the signal with regard to two objectives. In the first instance, they were asked to adjust the slider to the lowest position with which they could detect a difference (i.e., detection threshold). In the second instance, they were asked to adjust the slider to the position that was preferred. In both instances, participants adjusted the amount of gain that was applied to the lowered portion of the signal. However, participants were not informed with regard to how exactly the signal was being modified.

LTAS segment 1 LTAS segment 2 -20 -20 OV / LP OV / LP lowered signal lowered signal -30 HFLo -30 HFLo

-40 -40 dB dB -50 -50

-60 -60

-70 -70 0 1000 2000 3000 4000 5000 0 1000 2000 3000 4000 5000 Hz Hz

LTAS segment 3 LTAS segment 4 -20 -20 OV / LP OV / LP lowered signal lowered signal -30 HFLo -30 HFLo

-40 -40 dB dB -50 -50

-60 -60

-70 -70 0 1000 2000 3000 4000 5000 0 1000 2000 3000 4000 5000 Hz Hz

Figure 5:4 Long-term average spectra of the four music segments in the original version (OV) / LP condition, the HFLo condition and the spectra of the lowered signal for a gain weight of 0 dB.

146 Chapter 5: Harmonic Frequency Lowering

If the gain corresponding to the preferred position was higher than the gain corresponding to the detection threshold, the mean of the two gains was applied to the compressed signal in the HFL conditions. If the gain corresponding to the preferred position was lower than the gain corresponding to the detection threshold, the gain at the detection threshold was applied to the compressed signal in the HFL conditions. This last measure was necessary to ensure that there would always be a perceptual difference between HFL and LP signals. All versions of each segment were presented at an output level of 65 .

MAIN TEST

The setup of the main tests was a multi-stimulus test method similar to a MUSHRA setup as described by the recommendation ITU-R.1534 (2001). In each trial, participants had to compare and rate 5 stimuli versions on a scale from 0 to 100. The stimuli versions were original, NFC, HFLo, HFLi, and LP. A separate trial was carried out for each music segment. An example screen for one trial is displayed in Figure 5:5.

Figure 5:5 Example screen of the main test.

147 Chapter 5: Harmonic Frequency Lowering

The different conditions were randomly assigned to different buttons (A-E). Participants were asked to make judgments along two dimensions: music detail and sound quality. Music detail was further paraphrased to the participants as additional acoustic content that enriches the music such as instruments, melody parts, or rhythmic elements. It was made clear that artefacts or other audible effects that do not belong to music were not to be considered in the evaluation of detail. The intention with the detail dimension was to measure how much effect harmonic frequency lowering had on the audibility of music content. The intention with sound quality was to find out whether the perceivable lowered signal components were considered positive or detrimental from an aesthetic perspective. Participants were instructed to focus on the relative differences between the conditions within one trial rather than trying to make absolute ratings across trials. The scales used for the rating ranged from “low” to “high” for detail and “poor” to “good” for sound quality.

First, all trials for music detail were carried out. Then there was a pause. After the pause, all trials for sound quality were carried out. Participants conducted the test twice on two separate occasions, with one trial for every segment and question resulting in a total of 2 4 2 = 16 trials.

The stimuli were looped endlessly within their channel A , B, C, D, or E (c.f. Figure 5:5). As the original stimuli were selected to preserve musical phrasing, the transitions from the end to the beginning of each loop were unnoticeable. Participants were freely able to switch between stimuli or channels respectively at any given time. A 5-ms cross-fade was applied while channel switching in order to avoid switching artifacts such as cracks.

5.4 Results

5.4.1 Pretest The gain weights were specified as the energy difference between the compressed signal and the coinciding original signal in the spectral region within which the two signals overlap. Table 5:2 depicts the gain weights for the four music stimuli in the conditions HFLi and HFLo. Positive gain weights imply that the compressed signal was higher in level than the original signal in the overlap-

ping bandwidth.

A repeated-measures ANOVA was performed with measurement (threshold, preference), condition (HFLo, HFLi), and music segment (S1-S4) as within-subjects factors. As proposed by Girden (1992), in

148 Chapter 5: Harmonic Frequency Lowering cases where sphericity was violated, Greenhouse-Geisser corrections were used if the epsilon test statistic was lower than 0.75; otherwise, the Huynh-Feldt corrections were applied. There were no main effects of measurement or segment, but a significant main effect of condition (F 1,18 = 10.07, p = 0.005). The gain weights for the HFLi condition (mean: 4.42 ) were significantly higher than the gain weights for the HFLo condition (mean: 1.74 ).

Table 5:2 Gain weights in dB at the point of detection and preference for HFLi and HFLo.

Detection Preference HFLi HFLo HFLi HFLo 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

P1 -3 0.1 5.7 -1.7 -5.9 -1.3 -4.1 0.9 -9.2 -4 -6.4 -6 -7.6 -2.9 -8.2 -1.5 P2 -2.1 2.2 1.3 -3.5 -2.4 -2.6 -0.9 -3.5 -10 -3.4 -10 -6.1 -3.7 -6.1 -10 -10 P3 -0.6 6.4 3.2 5.1 -0.5 -0.4 1.9 -4.8 19 18 18 17 8.4 10 12 6.4 P4 -4.5 -7 -4.5 -3.4 -6.6 -4.2 -4.8 -6.6 -3 -0.2 -6.4 2.3 -4.4 -4.4 -3.2 -2.1 P5 1.4 -2.2 -0.8 2 8.2 3.1 4 5.8 12 13 9.2 11 7 8.1 10 7.6 P6 -0.6 0 -3.7 0 -2.5 -2.5 -2.5 -5 -10 -7.5 -7.5 5 -4.4 -7.5 -5 2.5 P7 3 6.1 2.8 5.9 -2.2 -1.3 6.8 1.9 3.8 -1.6 2.2 2.2 -4.4 -3.4 -2.2 -0.9 P8 2.2 2.2 1.2 0.5 2.3 1.6 0.9 6.1 0.9 6.8 -6.6 8.6 0.3 5.1 -1.6 7.1 P9 17 13 18 14 13 9 16 15 10 13 15 16 13 8.3 14 11 P10 2 8.8 -1 8 8 5 5 2 8 11 13 11 -1.9 -0.2 0.5 1.8 P11 -5.3 -4.3 1.4 -3.6 -3.5 -6.9 -0.5 -4.8 1.4 1 4 -0.3 -1 -3.2 1.7 -4.5 P12 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 P13 12 11 19 17 14 11 14 10 16 15 17 14 11 8.9 15 12 P14 9.7 12 10 9.5 -5.9 -6 -4.8 -5.3 9.5 8.9 10 10 -5.7 -5.2 -4.6 -4.3 P15 2.4 -1.1 2.2 1.5 0.8 -3.4 -1.3 0.8 1.2 -1.9 0.1 -3.7 0.1 -6 -4 2 P16 -0.4 0.5 -0.4 -1.3 -2.7 -2.4 -1.8 -2.5 -1.4 1.4 -1.3 -1.9 -2.6 -2.2 -1.7 -2.4 P17 -3 0.1 5.7 -1.7 -5.9 -1.3 -4.1 0.9 -0.1 6.3 0.1 5.6 -2 -0.2 -0.6 -1.8 P18 -6.6 -8.5 -7.6 -6.6 -8.2 -8.8 -4 -8.6 -10 -9.2 -7.5 -8.6 -10 -9.6 -6.1 -10 P19 12 18 17 13 9.7 9.5 13 8.5 19 17 21 14 14 10 15 12 MEAN 3 4 4.7 3.9 1.6 0.9 2.8 1.6 4 5.4 4.4 5.8 1.4 1 2.2 2.4

5.5 Main Test For music detail and music quality, a repeated-measures ANOVA was performed with session (test, retest), condition (Orig., NFC, HFLi, HFLo, LP), and segment (S1-S4) as the within-subject factors.

For music detail, there was no main effect of session or segment but a significant main effect of condition ( .,. = 44.49, < 0.001 ). The mean values and standard errors of the difference scores in all conditions are displayed in Figure 5:6. Participants perceived the most detail in the HFL conditions (HFLi: 68.6, HFLo: 72.1), followed by NFC (50.0), Original (47.8), and LP (41.7).

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Bonferroni-corrected pair-wise comparisons revealed significant differences between all conditions apart from Original vs. NFC, Original vs. LP, and HFLi vs. HFLo. The corresponding statistics are displayed in Table 5:3.

With regard to music quality, the effects of session and segment were not significant. Although the pattern of quality ratings across conditions were more or less consistent with the pattern obtained for detail (HFLo: 56.6, HFLi: 55.2, Original: 52.2, NFC: 51.8, and LP: 50.0), the effect of condition was not significant ( .,. = 1.27, = 0.290 ).

Figure 5:6 Mean ratings and standard errors for detail and quality in the 5 conditions under test (Orig: Original, NFC: nonlinear frequency compression, HFLi: harmonic frequency lowering with individual cut-off frequency, HFLo: harmonic frequency lowering with default cut-off frequency fc = 4 kHz, LP: low pass).

Table 5:3 Statistics of pair-wise ANOVAs for music detail between all 5 conditions. The Bonferroni-corrected significance level is p=0.005.

NFC HFLi HFLo LP

= 2.71 = 81 .87 = 50 .79 = 6.50 Orig , , , , = 0.117 < 0.001 < 0.001 = 0.020

= 52 .60 = 40 .42 = 10 .60 NFC , , , < 0.001 < 0.001 = 0.004

= 3.20 = 59 .49 HFLi , , = 0.090 < 0.001

= 49 .30 HFLo , < 0.001

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5.6 Discussion HFL conditions were found to be superior to all other conditions with respect to music detail. In addition, the HFL conditions did not have a detrimental effect on music quality. One interpretation of this finding is that high-frequency elements that were not audible in the original or low-passed filtered version of each segment became audible in the HFL conditions. The advantage of HFL over NFC for music detail may be explained by two factors: First, the frequency lowering in HFL is more aggressive than in NFC. Second, the maintenance of naturally occurring harmonic ratios in the HFL condition might preserve the naturalness of the signals better than NFC and therefore facilitate the detection of instruments, melody, harmony, rhythm, and other music details. Due to the preservation of the harmonic structure, the lowered-content tends to be considered musical. Although it would be possible to implement more aggressive NFC to improve the audibility of sounds with substantial high-frequency content, this would inevitably introduce even more harmonic distortion.

One criticism of the above interpretation of the music detail findings might be that the benefit was owed to the amount of gain applied to the frequency-lowered signal. If high gains are applied, the signal energy in the target region ends up being substantially higher in the HFL conditions than in the other conditions. The increase in energy was counterbalanced by normalizing all stimuli to the same RMS level before playback. Nevertheless, spectral differences between conditions might still contribute to variations in loudness and brightness. To address these potential effects, a post-hoc repeated-measures ANCOVA was performed with the gain weights as covariate. This post-hoc analysis revealed that the effect of the amount of gain on the perception of detail was not significant

(, = 0.259, = 0.617 ). In addition, a post-hoc repeated-measures ANOVA was performed on a subgroup of participants who assigned average gain weights of less than 0 to the frequency lowered signal. This post-hoc analysis yielded the same result as the original analysis: Both HFL conditions were superior to all other conditions in music detail ( ., = 13.13, = 0.002 ) without a detrimental effect on music quality ( .,. = 0.72, = 0.453). To further assess a potential bias of the increase in high-frequency energy on the results on detail, a follow-up study could be conducted in which the high-frequency energy of the other conditions is elevated to the same level. Like- wise, the RMS level of the high-frequency content in the HFL conditions could be adjusted to the RMS level of the high-frequency content in the original version.

With regard to music quality, participants did not have a clear preference for either condition. None of the participants had experienced frequency lowering prior to the experiment. Acclimatization to

151 Chapter 5: Harmonic Frequency Lowering relearn the new mapping in the auditory periphery might be necessary in order to appreciate an improvement in the sound quality of music. Several studies demonstrate a learning effect of frequency lowering for speech intelligibility (Kuk & Keenan 2010; Wolfe et al. 2010; Wolfe et al. 2011; Glista, Scollie, & Sulkers 2012) and the same might apply for sound quality of music and the perception of music detail.

As we instructed our listeners to respond to detail holistically, we do not know which attributes contributed exactly to the perception of detail. Based on a pretest and random post-hoc queries, we assume that the audibility of the high-frequency instruments such as cymbals and an improvement in the perception of the melodies mainly affected the detail ratings. The lack of performance- based measures such as instrument detection or melody discrimination task did not allow for further analysis.

5.7 Conclusion HFL is a novel frequency-lowering method that preserves the harmonic ratios inherent in the music signal. In this study, an overall improvement in the perception of music detail without detriment for quality was observed for two implementations of an HFL algorithm. Acceptance of the new algorithms might have been even stronger following an acclimatization period as participants had not previously experienced frequency lowering. Future research should consider how HFL can be opti- mally fitted and assess how its benefit may evolve with acclimatization.

Acknowledgments

We thank the participants for taking part in this study and for appearing to each session as scheduled. We further thank our colleagues for letting us occupy the laboratory facilities for six weeks of measurements.

The research protocol for this study was approved by grant (KEK-ZH. Nr. 2014-0520) from the Ethics Committee Zurich, Switzerland and was registered at http://clinicaltrials.gov (ID: NCT02373228).

152 Chapter 5: Harmonic Frequency Lowering

This research was supported by Phonak AG, ETH Zürich, and the Natural Sciences and Engineering Research Council of Canada.

The authors declare no other conflict of interest.

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160 Chapter 6: General Conclusion

Chapter 6 General Conclusion

Hearing loss impairs the perception of music and as a consequence the quality of life. The enjoyment of music is affected which implicates that the physical, mental, and social benefits of music are less well and less often experienced. The hearing research community and the hearing-aid industry, however, have focused on speech and the improvement of speech intelligibility. Only a few studies on music perception with hearing impairment have been conducted and there is a need and room for improving the signal processing of hearing aids for music perception in hearing-impaired listeners.

A new research tool was developed to analyze music perception in hearing-impaired and hearing- aided listeners. The Adaptive Music Perception (AMP) test allows for quantifying music perception by adaptively determining discrimination thresholds of different music dimensions. Participants perform tasks related to the perception of meter, harmony, melody, and timbre while the underlying low-level dimensions such as level or duration are adaptively manipulated. All discrimination thresholds are determined in a musically relevant framework so that the use of the tests corresponds more directly to functional hearing than a conventional assessment of discrimination thresholds. The adaptive nature of the test allows for testing all degrees of hearing loss with high sensitivity.

In the meter test, a sequence of six isochronous beats is played back. Accents on the strong beats are induced by changes in one of the low-level dimensions level, frequency, or duration. Partici- pants respond whether the sequence constitutes a duple or triple meter (grouping notes by two or three).

In the harmony test, two cadences composed of three dyad chords (root and fifth) are played back in succession. In one of the cadences, the stability of the last chord is manipulated by either increasing the pitch of only the fifth (dissonance) or of the dyad (intonation). Listeners make judgments about which of the two cadences is less resolved.

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In the melody test, two melodies are played back in the context of a chordal accompaniment that serves as a mask. Both melodies have either a different or the same contour and participants are asked to make a corresponding judgment. The difficulty of the task is adapted by manipulating the level of the melodies in proportion to the level of the chordal masker (melody-to-chord ratio). The second melody always starts one whole tone lower than the first melody to avoid that the melody recognition task can be circumvented by focusing on absolute pitches. The melody test includes two sets of melodies, one in the higher and one in the lower register of the chordal accompaniment.

In the timbre test, three tones with the same pitch, loudness, and duration are played back in succession. A difference in timbre is induced by manipulating the brightness, attack time, or spectral irregularity of one or two tones in the sequence. The participants are asked to decide whether the third tone sounds like the first or the second tone.

The AMP was administered on 19 normal-hearing and 21 hearing-impaired listeners to study the effect of hearing loss on music perception. An analysis of covariance of both groups with music experience as a covariate revealed significant detriments in music perception of the hearing-impaired group in seven physical dimensions related to the music dimensions meter, harmony, melody, and timbre. The thresholds for frequency discrimination in the meter test; dissonance and intonation in the harmony test; melody-to-chord ratio I and II in the melody test; and brightness and spectral irregularity in the timbre test were significantly elevated in the hearing-impaired group. Music experience had a significant positive effect on level (meter), frequency (meter) and intonation (harmony). Test-retest reliability was excellent (>0.8) for level (meter) and attack (timbre); acceptable (>0.6) for pitch and duration (meter), dissonance and intonation (harmony); and poor (<0.6) for spectral irregularity (timbre). There was a session effect in three of the ten low-level dimensions: frequency (meter), dissonance (harmony), and attack (timbre). The melody test appeared to be the most challenging as 12 participants were not able to carry out the test even in the absence of the chordal masker.

In a follow-up study with 25 hearing-impaired participants, the AMP test indicated that hearing aids may have a detrimental effect on meter and timbre perception based on marginally significant differences in discrimination thresholds for level and attack in hearing-aided versus unaided conditions. A post-hoc correlational analysis also revealed that the impairment in perception of attack is related to dynamic compression in hearing aids. Hearing aids apply dynamic compression to compensate for loudness recruitment in sensorineural hearing loss. The dynamic range between the

162 Chapter 6: General Conclusion hearing threshold and the uncomfortable loudness level is reduced so that the perception of loudness grows abnormally rapidly with increases in supra-threshold stimulus intensity. There are scientific prescription rules on how to amplify and compress speech but there is no established standard on how to compress music.

To guide the optimization of dynamic compression for music, an analysis of the dynamic range of music and speech was conducted. As the dynamic range of music may vary with instrumentation and style, the analysis of music was carried out for ten different genres independently: chamber music, choir, opera, orchestra, piano music, jazz, pop, rap, rock, and schlager. For each genre, 100 songs were collected in CD quality with 16-bit resolution and 44.1-kHz sampling rate. All music selected for analysis was released between 2000 and 2014 to minimize the historic change in production aesthetics that occurred prior to the 21 st century. For speech, 28 recordings from one female and one male native speaker in Chinese, English, Spanish, French, Japanese, German, Italian, Portu- guese, Hungarian, Bulgarian, Polish, Dutch, Slovenian, and Danish were used. The IEC 60188-15 standard was applied to calculate the individual dynamic range. From each song, a 45-s excerpt was cut out and filtered with third-octave bands. Within each band, the level was estimated in overlapping windows with duration of 125 . The dynamic range for each band was calculated as the difference in levels between the 99 th and 30 th percentiles.

The dynamic ranges of the modern genres (pop, rap, rock, and schlager) were smaller than the dynamic range of jazz and the dynamic ranges of the classical genres (chamber music, choir, opera, orchestra, and piano). All music genres generally had smaller dynamic ranges than speech. Speech was only locally surpassed by chamber music in the lowest two frequency bands ([ 110 to 177 ]) and by orchestra and opera in the lowest band ([110 to 140 ]). Based on these results, the hypothesis was proposed that music and especially music from modern genres require less dynamic compression than speech.

To test the hypothesis, a follow-up study with 31 hearing-impaired participants was conducted. Participants were individually fitted with Phonak Audéo V50 hearing aids according to the compression standard NAL-NL2 and wore them for at least five weeks prior to the experiment for the purpose of acclimatization. In the experiment, participants listened to triples of music stimuli and made judgments along the dimensions dynamics and sound quality. Twenty songs were tested, four from each of the genres choir, opera, orchestra, pop, and schlager. Music segments were selected at points consistent with musical phrasing. The triples of music stimuli in the test were generated by

163 Chapter 6: General Conclusion subjecting the music segments to one of three different dynamic processings: compressive, semi- compressive, or linear. The compressive setting corresponded to the individual NAL-NL2 parameter- ization. In the semi-compressive setting, half the compression of the NAL-NL2 standard was applied and in the linear setting, the amplification was constant over time. The average gain in all three settings was controlled within each frequency band so that the spectral shape of a music segment remained the same in each setting. Potential loudness differences between the settings were assessed with the Dynamic Loudness Model by Chalupper and Fastl (2002) and minimized if they ex- ceeded 1 .

The results confirmed that participants were able to perceive significant differences between the processing schemes across all genres. The linear setting was rated highest in dynamics, followed by the semi-compressive and the compressive setting. With regard to sound quality, the linear setting also yielded the highest ratings across all genres, followed by the semi-compressive and the compressive setting. The differences between the conditions were significant in all pair-wise comparisons. The results confirm that less compression benefits the perception of sound quality.

State-of-the-art hearing aids do not only apply compression on the dynamic range of a signal but also on the spectrum of a signal. The purpose of the so-called frequency lowering is derived from the same principle as the concept of dynamic compression: the hearing range of normal-hearing people is mapped to the limited hearing range of the hearing-impaired individual. Higher frequencies that are inaudible to the impaired ear are lowered to frequencies that can be made audible by conventional amplification. Frequency lowering in hearing aids, however, has focused on increasing speech intelligibility rather than improving music perception. State-of-the-art frequency-lowering algorithms violate the harmonic structure of music and their usability and benefit for music are controversial.

A novel frequency-lowering algorithm was developed for music. Harmonic frequency lowering preserves the pitch chroma and harmonic structure in music. High-frequency content is lowered by an octave and mixed with the original signal. To reduce masking of the lowered content by the original signal in the overlapping region, the lowered content is amplified before mixing. Harmonic frequency lowering was developed to increase the audibility of detail in music without harming its sound quality. The potential benefit was verified in an experiment with 19 hearing-impaired listeners. To avoid a bias, none of the participants had experienced frequency-lowering signal processing prior to the experiment. Music segments were selected as test material that contained substantial high-

164 Chapter 6: General Conclusion frequency content and spanned a range of genres. Two parameterizations of harmonic frequency lowering were opposed to the established frequency-lowering algorithm Sound Recover, a low-pass filter, and the original. The two harmonic frequency-lowering versions differed in their cut-off frequency, the frequency above which the signal was lowered. In one version, the cut-off frequency was the same for all participants and fixed at 4 . In the other version, the cut-off frequency was individually determined based on the cut-off frequency that Sound Recover proposed so that the frequency regions that were spectrally modified in both conditions coincided. Apart from the original, the bandwidths of all stimuli were the same and were aligned to the bandwidth of the established frequency-lowering algorithm Sound Recover.

In each trial, participants were asked to rate the five stimuli versions along the dimensions music detail and sound quality. Music detail was highest in both harmonic frequency-lowering conditions followed by Sound Recover, the original, and the low-pass filtered version. The differences were significant for all pair-wise comparisons between one of the two harmonic-frequency-lowering conditions and one of the three comparative conditions. With regard to sound quality, harmonic frequency lowering also yielded the highest results followed by the original version, the established algorithm, and the low-pass filtered version. The differences between conditions, however, were not significant. Harmonic frequency lowering appears to improve the perception of music detail in hearing-impaired listeners with no detriment to sound quality.

In summary, hearing loss and the use of hearing aids affect various dimensions of music perception. By adapting the dynamic compression and frequency lowering to the acoustic properties and harmonic requirements of music, music perception can be improved in hearing-impaired listeners. It was experimentally affirmed that hearing-impaired listeners benefit from linear dynamic processing and harmonic frequency lowering, a novel frequency-lowering strategy that preserves the pitch chroma and harmonic structure of music.

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Reference

Chalupper, J., & Fastl, H. (2002). Dynamic loudness model (DLM) for normal and hearing-impaired listeners. Acta Acustica United with Acustica , 88 (3), 378-386.

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Chapter 7 Outlook

7.1 Adaptive Music Perception Test Neither hearing loss nor hearing-aid signal processing showed an effect on the perception of signal duration (chapter 2 and 3). We therefore advise to remove this low-level dimension (D3) from the meter test so that the adaptive process will be faster.

The melody test was very challenging to participants because of the transposition. Participants had to detect whether the contours of two 4-note melodies were the same or different. The contour of either the first or the second melody was made different by interchanging the second and the third tone of the respective melody. The second melody presented during a trial was transposed by a whole tone to ensure that focusing on the absolute pitch of the second or third tone of a melody could not circumvent the melody recognition task. We recommend omitting the transposition in future uses of the AMP test.

Instead, the contour should be alterable not only by interchanging the second and third tone but by modifying any of the four tones from the melodies. Then, there is only a limited chance of 25% in lieu of 50% to circumvent the task by focusing on the absolute pitches of a melody.

7.2 Dynamic-Range Analysis and Dynamic Compression The dynamic analysis and signal-processing recommendations in this thesis were confined to recorded music as it accounts for most of the music we listen to. Listening to live music, however, is another use case for which hearing aids need to be improved. A potential distinction will have to be drawn between live music with and without electronic processing. While it is common in pop and rock concerts to apply dynamic compression at various stages such as to individual channels and to the master output, a classical performance is purely acoustic. Previous research has assessed the dynamic range of live music (Sivian, Dunn, & White 1931; Winckel 1962; Fielder 1995), but rather as level differences between the loudest peak and a reference (noise floor or average level) than with a temporal resolution that is relevant for loudness perception and/or dynamic compression in hearing aids as used in this thesis. Further investigations are needed to assess the dynamic properties of

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live music in a way that is meaningful for loudness perception and hearing-aid signal processing as proposed in this thesis. A challenge for hearing aids will be the processing of peaks above 110 as they are often experienced in live music (Sivian, Dunn, & White 1931; Winckel 1962; Wilson et al. 1977; Cabot et al. 1978; Fielder 1982; Ahnert 1984).

Besides listening to live music, another area that needs improvement is how hearing aids should be parameterized when the hearing-aid user plays an instrument. Previous research has examined the dynamic ranges of musical instruments, but also rather through comparing the levels at soft and loud passages than with a temporal resolution that is relevant for loudness perception and/or dynamic compresion in hearing aids (Clark & Luce 1965; Miskiewicz & Rakowski 1994). Another factor that weakens the usability of those studies is the fact that the sound pressure measurement devices were not located at the position of the instrument players’ ears. A challenge will also be the high sound pressure levels that single instruments can generate (Ahnert 1984; Krämer 2011). More research in this area is necessary and especially important as music is a vital aspect of life for musically active hearing-impaired people.

7.3 Harmonic Frequency Lowering The concept of preserving the harmonic structure and pitch chroma in harmonic frequency lowering by octave transposition can be extended to 2 octaves. An example is displayed in Figure 7:1. The strategy could especially be beneficial for listeners with severe to profound hearing losses. It allows

4 fout kHz

2 4 6 8 f kHz in

Figure 7:1 Example input-output function (solid line) for harmonic frequency lowering with double octave transposition.

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for significantly lowering high-frequency content without violating the harmonic ratios. Neverthe- less, mutual masking of the lowered signals and the original signal might lessen the benefit in audibility. Future experiments will reveal how much benefit this approach will generate for hearing- impaired listeners.

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References

Ahnert, W. (1984). The sound power of different acoustic sources and their influence in sound engineering. Presented at the 75 th Convention of the Audio Engineering Society, Journal of the Audio Engineering Society, 32 , 464.

Cabot, R. C., Genter, I. I., Roy, C., & Lucke, T. (1978). Sound levels and spectra of rock music. Journal of the Audio Engineering Society , 27 (4), 267-284.

Clark, M., & Luce, D. (1965). Intensities of orchestral instrument scales played at prescribed dynamic markings. Journal of the Audio Engineering Society , 13 (2), 151-157.

Fielder, L. D. (1982). Dynamic-range requirement for subjectively noise-free reproduction of music. Journal of the Audio Engineering Society , 30 (7/8), 504-511.

Fielder, L. D. (1995). Dynamic-range issues in the modern digital audio environment. Journal of the Audio Engineering Society , 43 (5), 322-339.

Krämer, J. (2011). Sound power of modern and historical orchestral instruments. Magister thesis, Technical University Berlin.

Lebo, C. P., & Oliphant, K. P. (1968). Music as a source of acoustic trauma. The Laryngoscope , 78 (7), 1211-1218.

Miśkiewicz, A., & Rakowski, A. (1994). Loudness level versus sound ‐pressure level: A comparison of musical instruments. The Journal of the Acoustical Society of America , 96 (6), 3375-3379.

Sivian, L. J., Dunn, H. K., & White, S. D. (1931). Absolute amplitudes and spectra of certain musical instruments and orchestras. The Journal of the Acoustical Society of America, 2(3), 330-371.

Wilson, G. L., Attenborough, K., Galbraith, R. N., Rintelmann, W. F., Bienvenue, G. R., & Shampan, J. I. (1977). Am I Too Loud? (A Symposium on Rock Music and Noise-Induced Hearing Loss). Journal of the Audio Engineering Society, 25 (3), 126-150.

Winckel, F. W. (1962). Optimum acoustic criteria of concert halls for the performance of classical music. The Journal of the Acoustical Society of America , 34 (1), 81-86.

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