Loudness: Current Knowledge and Questions
ITU-T Workshop on "From Speech to Audio: bandwidth extension, binaural perception" Lannion, France, 10-12 September 2008
Loudness: Current Knowledge and Questions
Sabine Meunier, Laboratoire de Mécanique et d’Acoustique – CNRS - France
International Telecommunication Lannion, France, 10-12 September 2008 Union Loudness
Supraliminary sensation: how to measure it ?
Weber-Fechner law, 19th century
Weber: ΔΦ/Φ=constant Φ:stimulation
Fechner:ΔΨ=k ΔΦ/ΦΨ: sensation
Ψ = A LogΦ + B
Stevens law: direct measurement, magnitude estimation
b Ψ = a Φ International Telecommunication Union 2 Lannion, France, 10-12 September 2008 Methods to measure Loudness
Magnitude estimation: loudness in sones 1 sone = loudness of a 1-kHz tone at 40 dB SPL
Adjustement (loudness matches): loudness level in phons a loudness level of a sound of X phons means that the sound is as loud as a 1-kHz tone at X dB SPL
Adaptive (2down–1up, 1down–2up): loudness level in phons
Multitracking: loudness level in phons
Categorical loudness scaling
International Telecommunication Union 3 Lannion, France, 10-12 September 2008 Methods to measure Loudness Adjustment Test sound (T): the sound that we want to know the loudness
Sound of comparison (C): usually 1-kHz tone, variable level
C after T (1st test) and T after C (2nd test)
Listener’s task: Adjust the C-level to have the same loudness as T
Random order, different for each listener
Start level was randomly X dB above or under T loudness level
International Loudness level in phons : mean of C-level obtainedTelecommunication in Union 4 Lannion,the France, 2 tests 10-12 September for 2008each sound Methods to measure Loudness
Magnitude estimation: loudness in sones 1 sone = loudness of a 1-kHz tone at 40 dB SPL
Adjustement (loudness matches): loudness level in phons a loudness level of a sound of X phons means that the sound is as loud as a 1-kHz tone at X dB SPL
Adaptive (adown–bup, bdown–aup): loudness level in phons
Multitracking: loudness level in phons
Categorical loudness scaling
International Telecommunication Union 5 Lannion, France, 10-12 September 2008 Methods to measure Loudness adaptive methods
Presentation order : T & C or C & T, randomly 2down-1up (1st test) : Listener’s task : Which of these 2 sounds is louder Start level above the T loudness level ++ -5 dB 2nd reversal Mean of the last Y reversals ++ ++ -5 dB -2 dB --+5 dB + JL 1st reversal Track finishes after X reversals Loudness 2up-1down (2nd test) : level in phons 1st reversal ++ +5 dB +2 dB - JS -- -5 dB -- +5 dB 2nd reversal International -- Telecommunication Start level under the T loudness level Union 6 Lannion, France, 10-12 September 2008 Methods to measure Loudness
Magnitude estimation: loudness in sones 1 sone = loudness of a 1-kHz tone at 40 dB SPL
Adjustement (loudness matches): loudness level in phons a loudness level of a sound of X phons means that the sound is as loud as a 1-kHz tone at X dB SPL
Adaptive (2down–1up, 1down–2up): loudness level in phons
Multitracking: loudness level in phons
Categorical loudness scaling
International Telecommunication Union 7 Lannion, France, 10-12 September 2008 Methods to measure Loudness Multitracking
Principle similar to the adaptive method 4 or 5 simultaneous sequences Random choice of the sequence, different for each listener Loudness level in phons: mean of +JL and –JS for each sound
International Telecommunication Union 8 Lannion, France, 10-12 September 2008 Methods to measure Loudness
Magnitude estimation: loudness in sones 1 sone = loudness of a 1-kHz tone at 40 dB SPL
Adjustement (loudness matches): loudness level in phons a loudness level of a sound of X phons means that the sound is as loud as a 1-kHz tone at X dB SPL
Adaptive (2down–1up, 1down–2up): loudness level in phons
Multitracking: loudness level in phons
Categorical loudness scaling
International Telecommunication Union 9 Lannion, France, 10-12 September 2008 Methods to measure Loudness Categorical loudness scaling
50 too loud Loudness measured in 45 very loud Categorical Unit (CU) 40 35 loud 30 25 medium 20 15 soft 10 5 very soft 0 inaudible International Telecommunication Union 10 Lannion, France, 10-12 September 2008 Loudness as a function of SPL
a 200 N=k(P-P0) 100 50 at 1 kHz: a=0.6 20 10 N: loudness 5.0 8000 Hz P: pressure 2.0 4000 Hz P0: constant 1.0 0.5 0.2 1000 Hz Loudness in sones 0.1 100 Hz .05 z 250 Hz H
0 .02 0 5 0 20 40 60 80 100 120 From Scharf (1978)International in Telecommunication Sound pressure level (dB) Handbook of perception,Union 11 Lannion, France, 10-12 September 2008 Carterette and Friedman Loudness as a function of SPL Partial loudness
50
20
10
5.0
2.0
1.0
Loudness in sones 0.5
0.2 Quiet 50 60 70 80 90 100 dB SPL of Noise 0.1 20 30 40 50 60 70 80 90 100 110 From Scharf International(1978) in SPL of masked tone (dB) Handbook ofTelecommunication perception, Union 12 Lannion, France, 10-12 September 2008 Carterette and Friedman Loudness as a function of frequency Equal loudness contours Standard: ISO 226, 2003 sound pressure level (dB)
International frequency (Hz) Telecommunication Union 13 Lannion, France, 10-12 September 2008 Loudness as a function of frequency Equal loudness contours
90 ISO226 2003 ISO226 1987 80 75 phons
70 60 phons 60 50 phons 50 Sound Pressure Level (dB) Pressure Sound From Boullet (2005) 40 PhD Thesis 100 1000 10000 International Telecommunication Frequency (Hz) Union 14 Lannion, France, 10-12 September 2008 Loudness as a function of bandwidth Spectral loudness summation
overall sound presure level
From Scharf (1978) in Handbook of perception, critical band Carterette and Friedman Loudness level in phons Loudness International Telecommunication Bandwidth (Hz) Union 15 Lannion, France, 10-12 September 2008 Loudness as a function of duration Temporal loudness summation 72 1-kHz pure tone 70
68
66
64
62
60 y = 71.2+10*log(1-exp(-x/0,127))
Loudness level (phons) R² = 0,93 58 τ = 127 ms From Boullet (2005) Critical duration = 381 ms PhD Thesis 56 0,01 0,1 1 International Telecommunication Duration (s) Union 16 Lannion, France, 10-12 September 2008 Loudness models Standards for steady sounds
ISO 532B, « Method for calculating loudness level », International Organisation for standardization (1975). From Zwicker E., Acustica, 10, 304 (1960) Zwicker E., J. Acoust. Soc. Am., 33, 248 (1961)
ANSI, S3.4-2005, « Procedure for the Computation of Loudness of Steady Sounds, », American National Standards Institute, New York (2005). From Moore B. C. J. and Glasberg B. R., Acustica-Acta Acustica, 82, 335 (1996). Moore B. C. J., Glasberg B. R., Baer T., J. Audio Eng. Soc.,
45, 224 (1997). International Telecommunication Union 17 Lannion, France, 10-12 September 2008 Zwicker’s model Stationary sounds, free or diffuse field
Signal
FFT
a0 filtering From free field to inner ear
aD+ filtering From free field to diffuse field Critical bands or 1/3 octave bands
1 24 Excitation Calculated using masking curves
Specific loudness Based on Stevens law
=Σ specific loudnesses Overall loudness International Telecommunication (because of spectral loudness summation)Union 18 Lannion, France, 10-12 September 2008 Moore and Glasberg’s model Stationary sounds, free or diffuse field
Based on Zwicker’s model
Differences: 1 –Auditory filters shapes, 2 –Excitation pattern,
3 - a0 and aD+
International Telecommunication Union 19 Lannion, France, 10-12 September 2008 Loudness models for non- stationary sounds
Zwicker E., “Procedure for calculating loudness of temporally variable sounds”, J. Acoust. Soc. Am., vol.62, n°3, 675-682, 1977.
Zwicker E. et Fastl H., “Psychoacoustics: Facts and models”, 2nd Edit ion, Springer-Verlag, Berlin, 1999.
Glasberg B. R. and Moore B. C. J., “ A model of loudness applicable to time-varying sounds”, J. Audio Eng. Soc., 50, n°5, 331-342, 2002.
International Telecommunication Union 20 Lannion, France, 10-12 September 2008 Current researches
Loudness of non-stationary sounds Short duration signals Long duration signals Effect of context Induce Loudness Reduction (Recalibration) Loudness Constancy Binaural Loudness Summation Spectral loudness summation and duration
International Telecommunication Union 21 Lannion, France, 10-12 September 2008 Loudness of non-stationary sounds Short duration sounds
20 Temporal integration =
Lshort –Llong ) indB
long 15 short and long signal at
-L equal loudness
short Temporal integration 10 depends on level Temporal integration maximum for moderate 5 Short varied levels Long varied
Level Difference (L Difference Level 0 20 40 60 80 100 120 Level of Short Tone in dB SPL International Telecommunication Union 22 Lannion, France, 10-12 September 2008 From Florentine et al., JASA 1996 Loudness of non-stationary sounds Short duration sounds
Loudness functions are not linear
Modified Power Function 200-ms Equal-Ratio Loudness 20 5-ms Equal-Ratio Loudness ) in dB
long 15 -L short 10
Lshort –Llong =14dB 5 Short varied
Long varied Lshort –Llong =19dB
Level Difference (L 0 20 40 60 80 100 120 International Level of Short Tone in dB SPL Telecommunication Union 23 Lannion, France, 10-12 September 2008 From Florentine et al., JASA 1996 Loudness of non-stationary sounds Short duration sounds
These loudness functions show features similar to the mechanical input/output measurement at the basilar membrane Temporal integration of loudness does not depends on level
International Telecommunication Union 24 Lannion, France, 10-12 September 2008 Loudness of non-stationary sounds Environmental short-duration sounds Most studies: Environmental sounds: Rectangular envelope Exponential envelope
N = kEaTb N: loudness E: energy T: sound duration International a, b: constants Telecommunication Union 25 Lannion, France, 10-12 September 2008 From Meunier et al., ICA 2001, Forum Acusticum 2002 Loudness of non-stationary sounds Environmental short-duration sounds
N= kEaTb Determination of a and b a: loudness functions for environmental short duration sounds b: loudness as a function of duration
International Telecommunication Union 26 Lannion, France, 10-12 September 2008 Loudness of non-stationary sounds Environmental short duration sounds Loudness as a function of duration
Three relationships between loudness and duration were found in different studies : - Loudness is constant when Energy is constant: Equal energy rule for duration less than the critical duration loudness = constant if Energy = Intensity x duration = constant
- Loudness is constant when Energy decreases as duration increases
- Loudness is constant when Energy
increases as duration increases International Telecommunication Union 27 Lannion, France, 10-12 September 2008 Loudness of non-stationary sounds Environmental short duration sounds Loudness as a function of duration
T 2 Energy = =∫ )(( dttpE = constant 0
International Telecommunication Union 28 Lannion, France, 10-12 September 2008 From Meunier et Rabau., Acoustics 08 Loudness of non-stationary sounds Environmental short duration sounds Loudness as a function of duration
88 dB HL 60dB SL 73 dB HL 45dB SL 58 dB HL When Energy constant, Loudness varies as a power function of 1 Signal Duration. Exponent depends on the level of the signal. Softer signals: bands of noise Loudness constant when Energy (normalized) F0=1 kHz decreases as duration increases Δf= 80 Hz Estimated loudnessEstimated Louder signals: 0,1 1 10 100 1000 Loudness constant when Energy Duration (ms) constant as duration increases International Telecommunication Union 29 Lannion, France, 10-12 September 2008 From Meunier et Rabau., Acoustics 08 Loudness of non-stationary sounds Loudness Model for Impulsive Sound (LMIS)
100 90
80 70 60 50 40 Measured Loudness Level 30 LMIS
Loudness Level (phons) Level Loudness 20 son23 son22 son02 son03 son24 son09 son15 son01 son06 son04 son13 son19 son16 son20 son08 son12 son11 son17 son18 son07 son21 son14 son10
son05_L3 son05_L2 Soundson05_L1 n° International Telecommunication Union 30 Lannion, France, 10-12 September 2008 From Boullet et al. in preparation Loudness of non-stationary sounds Long duration sounds
How does listeners judge overall loudness of time-varying sounds ?
Loudness N N10 N5 ?
1 min Time (s) International Telecommunication Union 31 Lannion, France, 10-12 September 2008 Loudness of non-stationary sounds Long duration sounds
Kuwano and Namba (Psychol. Res., 1985) and Fastl (5th Oldenburg Symp. Psych. Acoutics, 1991): Sound events proeminent in level strongly influence global loudness Susini et al. (Acta Acustica, 2002): Recency effect: related to the temporal position of the highest contour peak
Global loudness: combination of highest levels, of their temporal position and their duration of
International emergence Telecommunication Union 32 Lannion, France, 10-12 September 2008 Loudness of non-stationary sounds Temporal asymmetry
Loudness change of tones with linearly varying levels
Loudness change: asymmetric
Asymmetry depends on: direction of change (increasing vs. decreasing) range of levels (high vs. low).
International Telecommunication Union 33 Lannion, France, 10-12 September 2008 John G. Neuhoff , Nature, 1998, 395, 123-124 Loudness of non-stationary sounds Temporal asymetry
International Telecommunication Union 34 Lannion, France, 10-12 September 2008 John G. Neuhoff , Nature, 1998, 395, 123-124 Loudness of non-stationary sounds Temporal asymetry
100 A) - Pure tones at 1 kHz
(17 subjects) 75->45 decreasing 45->75 increasing 60->75 increasing 75->60 decreasing
10 Ratio of estimations of Ratio (Louder divided by softer) by divided (Louder
1 110100 Sweep duration in seconds
International Telecommunication Canévet et al., Acta Acustica,Union 2003 35 Lannion, France, 10-12 September 2008 Effect of context Induced Loudness Reduction (ILR)
A preceding higher-level tone (inducer) reduces the loudness of a lower-level tone (test tone)
A: 500-Hz tones relatively low SPLs and 2500-Hz tones high SPLs B: reverse
International Telecommunication Marks, J. Acoust. Soc.Union Am., 199636 Lannion, France, 10-12 September 2008 Effect of context Induced Loudness Reduction (ILR)
Amount of ILR depends on: Tone levels Frequency separation between inducer and test tone Duration of inducer and test tone Time separation between inducer and test tone Individual differences
International Telecommunication Review in Epstein, J. Acoust. Soc. Am., Online,Union 2007 37 Lannion, France, 10-12 September 2008 Effect of context Loudness Constancy
source power Intensity changes at the ear may be due to • Source power changes • Source distance source power
Loudness Constancy Loudness contant for fixed source source power and variable power source distance
International Telecommunication Zahorik and Wightman, Nature neuroscience,Union 2001 38 Lannion, France, 10-12 September 2008 Effect of context Binaural Loudness Summation (BLS) Binaural loudness = A x monaural loudness A: from 1.3 to 2 depending on study
International Telecommunication From Marozeau et al. J. Acoust. Soc. UnionAm., 2006 39 Lannion, France, 10-12 September 2008 Effect of context BLS as a function of stimulus and listening conditions
Stimuli Listening conditions • Monitored Live Voice (MLV) • Earphone spondees • Loudspeakers • Recorded spondees • Tones
BLS for tones or recorded spondees > BLS for MLV BLS for earphones > BLS for Loudspeakers
BLS in laboratory conditions > BLS out of the laboratory
International Telecommunication From Florentine J. Acoust. Soc. Am., Union2008 40 Lannion, France, 10-12 September 2008 International Telecommunication Union 41 Lannion, France, 10-12 September 2008 International Telecommunication Union 42 Lannion, France, 10-12 September 2008 Excitation
Masking curves
International Telecommunication Union 43 Lannion, France, 10-12 September 2008 Experiment 1 Loudness of synthesized noises
Physical parameters of the twelve synthesized noises
sound Central bandwidth Level num ber frequency (H z) (d B S P L ) (H z) 1 400 50 40 2 400 420 40 3 400 50 60 4 400 420 60 5 1420 120 30 6 1420 1000 30 7 1420 120 50 8 1420 1000 50 9 3000 240 60 10 3000 2040 60 11 3000 240 70 12 3000 2040 70
8 listeners
International Telecommunication Union 44 Lannion, France, 10-12 September 2008 From Meunier et al. InterNoise 2000 Experiment 1 : synthesized noises
y = 1,893 + 0,95909x R= 0,98632 90 11 12 80 Zwicker's model 4 10 70 3 9 6 60 5
(phons) 2 50 1 8 40 7 Adjusted loudness 30 30 40 50 60 70 80 90 Calculated loudness (phons)
y = 0,8725 + 0,9377x R= 0,99454 90 Moore's model (Acustica) 80 70 11 12 4 10 60 3 9
(phons) 6 50 5 40 2 Adjusted loudness 1 30 7 8 30 40 50 60 70 80 90 Calculated loudness (phons) y = 7,5766 + 0,85313x R= 0,97504 90 11 12 80 Moore's model (AES) 4 10 3 9 70 6 60 5 2 1 (phons) 50 8 7 40 7
Adjusted loudness International 30 Telecommunication 30 40 50 60 70 80 90 Union 45 Lannion, France, 10-12 September 2008 Calculated loudness (phons) From Meunier et al. InterNoise 2000 Experiment 1 Loudness of environmental noises
Twenty four enrironmental sound (steady over 1 s) Sound Abbreviation Blowlamp Blowlamp Guitare Guitare Harmonica Harm Rumpled paper Paper Computer hard disk Disk Telephon in an Anecho•c Chamber Tel_AC Telephon in an office Tel Bicycle in an Anecho•c Chamber Bicy_Ac Bicycle Bicy Car Car Woman voice Voice_W Man voice Voice_M Flute at 39 dB SPL Flute_39 Flute at 54 dB SPL Flute_54 Flute at 69 dB SPL Flute_69 Flute at 84 dB SPL Flute_84 Motorcycle at 28 dB SPL Moto_28 Motorcycle at 43 dB SPL Moto_43 Motorcycle at 58 dB SPL Moto_58 Motorcycle at 73 dB SPL Moto Drilling at 35 dB SPL Drill_35 Drilling at 50 dB SPL Drill_50 24 listeners Drilling at 65 dB SPL Drill_65 International Drilling at 80 dB SPL Drilling Telecommunication Union 46 Lannion, France, 10-12 September 2008 From Meunier et al. InterNoise 2000 Experiment 2 : environmental noises
y = 15,611 + 0,77787x R= 0,98295 100 90 Zwicker's model 80 70 60 (phons) 50
Adjusted loudness 40 30 30 40 50 60 70 80 90 100 Calculated loudness (phons)
y = 3,6762 + 0,87937x R= 0,97893 100 Moore's model (Acustica) 90 80 70
(phons) 60 50 Adjusted loudness 40 40 50 60 70 80 90 100 Calculated loudness (phons)
y = 8,587 + 0,82236x R= 0,96235 100 Moore's model (AES) 90 80 70
(phons) 60 50 Adjusted loudness International 40 40 50 60 70 80 90 100 Telecommunication Union 47 Calculated loudness (phons) Lannion, France, 10-12 September 2008 From Meunier et al. InterNoise 2000