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2014 Primo Passaggio Transition Gestures in Trained Female Singers Emily Craven

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Abstract

Varying techniques are implemented by trained singers to perceptually achieve evenness of tone. The purpose of this study is to investigate those who achieve this evenness effectively through examining the vocal fold closure and vocal tract acoustic adjustments made by trained female singers. The singers varied in their level of experience from undergraduate students in a vocal performance program to faculty members of the program and non-university professional vocal performers. The singers produced the vowel [a:] in an ascending scale through to octave

A3-A4 into a microphone. In addition to the microphone, electrodes were positioned over her thyroid to record the EGG of the signal. The EGG provides information on the closing quotient

(CQ) duration and fundamental frequency (f0) whereas the microphone provides information on

FFT spectral measurements of the frequency and amplitude of the harmonic with the greatest amplitude. The information from the two signals provides the points of measurement reflecting changes in the glottal signal and changes in the vocal tract resonances. The patterns of CQ and vocal tract resonance adjustments through the passaggio will be reported for the singer.

The Florida State University

COLLEGE OF COMMUNICATION

PRIMO PASSAGGIO TRANSITION GESTURES IN TRAINED FEMALE SINGERS

By

EMILY CRAVEN

A Thesis submitted to the Department of Communication Science and Disorders in partial fulfillment of the requirements for graduation with Honors in the Major

Degree Awarded:

Spring, 2014

The members of the Defense Committee approve the thesis of Emily Craven defended on April 4, 2014.

______

Dr. Richard Morris

Thesis Director

______

Professor David Okerlund

Outside Committee Member

______

Dr. Kaitlin Lansford

Committee Member

Primo Passaggio Transition Gestures in Trained Female Singers

Emily Craven

Richard Morris

INTRODUCTION

Accurate knowledge of the behaviors underlying trained singing has increased as the

technology for analyzing the acoustics and physiology of the speech mechanism has imporved.

One aspect of singing of interest to researchers has been the ability of trained singers to change

registers with no or minimal perceptual change. The changing of singing registers is referred to as a

passaggio. This ‘passage’ requires the singer to produce adjacent tones with equal timbre, even

across the different registers (Bjorkner, Sundberg, Cleveland, & Stone, 2005). The research on the

production of these tones varies from investigation of the laryngeal muscles in the regulation of the

fundamental frequency (Hirano, Ohala, & Vennard, 1969) to comparisons of the formants and

harmonics in different styles of singing (Hertegard, Gauffin, & Sundberg, 1990). In general, it has

been reported that the singers make similar vocal tract adjustments when singing through their

passaggio across different types of singing and speaking (Hertegard, et al., 1990; Svec, Sundberg,

& Hertegard, 2007; Large, 1972). These adjustments can, and often do, affect the acoustic

qualities of the sound.

Singers make physical adjustments in their vocal tract between the vocal registers. Two

singing styles have been of interest to researchers; these are covered and open singing (Hertegard,

et al., 1990). Covered singing is perceived as a darker vocal quality and open singing is associated

with a brighter timbre or quality (Hertegard, et al., 1990). Although some may prefer the brighter

timbre to the darker timbre, this technique is both more effective for the primopassaggio and is a healthier option for singers (Hertegard, et al., 1990). Hertegard and colleagues (1990) reported that singing with the brighter timbre requires the singer to pull up the larynx, which delays the register transition and increases the potential of damage and strain on the vocal folds. In covered singing, the vocal tract as a whole is lengthened through the widening of the laryngeal ventricles,

supraglottal tract, and hypopharynx, and elevation of the velum (Hertegard, et al., 1990). In the

1930s, Weiss attempted to prove that vocal tract length plays a role in register transition in singing

by having singers sing scales into varying lengths of glass tubing (Large, 1972). This experiment

seemed to exemplify the breaks between registers; however, Weiss did not account for the resonant qualities of the glass tubing compared to the vocal tract. Despite this lack of consideration, Weiss’ finding still supported the theory of supraglottal coupling of the speech mechanism (Large, 1972).

The two singing techniques are comparable in terms of vocal health of singers. Using the brighter timbre has the potential to lead to problems with voice health such as edema or nodules, as a result of overstretching and tensing the vocal ligaments (Hertegard, et al., 1990). This technique appears to stress the laryngeal muscles, despite the activity drop of the vocalis muscle.

For these reasons, Hertegard and colleagues (1990) claimed that implementing the darker timbre is the better option in an attempt to prevent hyperfunctional strain. Male singers should hypothetically use the darker timbre to pass through the primopassaggio successfully; however, it

can cause vocal strain due to the suppression of the larynx.

Acoustic differences can always be observed across the notes sung regardless which

technique is implemented (Titze, 2008). In untrained female singers, although the primopassaggio

was generally not as smooth as trained singers, the change is accompanied by the fundamental

frequency surpassing the frequency of the first formant (Svec, Sundberg, and Hertegard, 2007).

When the fundamental frequency approaches the first formant the primopassaggio is perceptually clear in the untrained singer. According to Titze (2008) when the fundamental frequency or harmonics are near the formants certain instabilities occur in the voice. These frequency

instabilities are referred to as “frequency jumps,” and are a result of a sudden change in acoustic

reactance from changing registers. These frequency jumps positively correlate with coupling,

meaning that larger frequency jumps occur with greater coupling (Titze, 2008). An increase in

coupling is due to a narrowing of the epilarynx tube according to Titze (2008) and Appleman

reported this increased coupling for each register change (Large, 1972).

Although much of the research suggests that laryngeal muscles and technique contributes

to the successful primopassaggio, Miller and Schutte (2005) claim that female singers do not successfully mix registers because of muscular adjustments but instead because of using resonance adeptly. They also noted that successfully matching tones in two different registers correlated with a minimal difference between the closed quotients of the registers. Large (1973) believes that successfully matching tones, or register equalization, can be attributed to timbre. Large (1973) found that if the timbre differences were minimal then the tones were less likely to be identified in the proper register, meaning that the singer was capable of producing the same tone in two different registers. He said that the differences in timbre were found to be a result of different source waveforms (Large, 1973). Titze (2008) agreed with Large in respect to laryngeal effects on timbre. Titze (2008) found that the entire spectrum of source frequencies can be produced without vocal fold collision when the harmonics are below the first formant. These differences in laryngeal activity do not seem to affect the ability of a singer to achieve a primo passaggio transition deemed successful by listeners. However, the technique a singer chooses to use as well as her ability to regulate the tone and timbre are factors in the perception of a successful primo passaggio transition. Given the different techniques that can create evenness of tone through the primo

passaggio, the purpose of this study is to investigate the adjustments in vocal fold closure and vocal tract acoustics made by trained female singers when singing through the primo passaggio. It is hypothesized that these singers will exhibit a marked drop in CQ from the lowest note in the octave to the highest. However, these singers will not exhibit the precipitous CQ drop observed in the speaking voice transition from modal to falsetto register. A second hypothesis is that the third harmonic (H3) will have the greatest amplitude for the lower notes in the octave, whereas the second harmonic (H2) will have the greater amplitudes for the higher notes. The third hypothesis is that the harmonic at which the singer’s formant occurs will exhibit a noticeable drop when the singers transition from the chest to mixed voice.

METHOD

Subjects

The subjects consisted of a group of 15 females ranging in vocal training. Five of the singers were undergraduate students enrolled in a competitive audition based vocal performance program, six were graduate students of a vocal performance program, and the remaining four were professional singers. The singers did not report any vocal health problems nor did the experimenters observe any voice or speech disorders at the time of data collection.

Recording Procedure

Each singer completed an FSU IRB Committee approved informed consent form and a questionnaire to report her vocal category, years of singing training, hours of daily/weekly practice, current voice teacher, and recent performance roles. She was then given time to perform her typical vocal warm up exercises. Once she felt her voice was ready, the singer was centered in front of an AT 3036 omnidirectional condenser microphone at 30 cm away with the microphone positioned at a 45 degree angle toward her side and at mouth level. It was connected to a PC computer where the signal was digitized and directed to the first channel of the Voce Vista Pro software (version 3.2).

She also had the electrodes of a Voce Vista electroglottograph (EGG) positioned over her thyroid laminae and held in position using an elastic and Velcro strap. The PC computer also digitized the

EGG output and sent it to the second channel of the Voce Vista Pro software. The Voce Vista

Pro software digitized the signals from both channels at a rate of 22500 samples per second. The signals for each activity were saved as a file on the computer.

Each subject was instructed to sing the vowel [a:] in an ascending scale through the octave

A3-A4 at a comfortable mezzoforte level. The scales were sung at a tempo of approximately one note per second. A cell phone based tuner was used to assist in setting a beginning pitch. The singers were cued to the beginning pitch by an experimenter before each scale was sung.

Measurement Procedure

Two sets of measurements were taken using the recordings by the selected singers. The first set included EGG measurements including closing quotient (CQ) duration and fundamental frequency (f0). The second set included FFT spectral measurements of the frequency and amplitude of the harmonic with the greatest amplitude. Different routines of the Voce Vista software were used to provide the different signal displays for measurement. EGG shape differences represented changes in the glottal signal, whereas spectral shape differences represented changes in the vocal tract adjustments to the signal. The specific points for measuring the data were selected using the Voce Vista’s narrow-band spectrogram display. Vibrato frequency peaks and troughs for each note were selected for measurements. These selections were used for both sets of measurement.

In comparison to the EGG signal, the acoustic signal was slightly delayed so the two signals were aligned for the first set of measurements. To align the signals, the audio signal was delayed between 1.30 and 1.45 ms, so that a vertical cursor marked the rapid rise in both the EGG and audio signals. Variations in the delay were caused by slight differences between singers in the mouth-to-microphone distance. The Voce Vista software display of the CQ in the EGG signal window was recorded. The CQ value indicated the proportion of the EGG cycle that the vocal folds were closed to some degree. The CQ was determined by the placement of the first vertical cursor to mark the onset of the rapid rise in the EGG and audio signals and the second vertical cursor to mark the final peak of the acoustic signal before reducing to lower amplitude levels at the end of each vocal cycle. The f0 was recorded from the display in the audio signal window of the

Voce Vista software.

The second set of data measurements, the spectral data, was measured from an FFT display of the data. The window size of the FFT was 2048 with an analysis frame of 10.8 Hz. The harmonic amplitude in the FFT window was displayed as a value down from 100 dB. A vertical cursor was used to mark the amplitudes of the first five harmonics and the number of the peak harmonic of the singer’s formant. The frequencies and amplitudes for the selected harmonics were displayed by the Voce Vista software and these numbers were recorded.

The measurements from the vibrato peaks and troughs for each note sung by each subject were averaged and the averages from the vibrato peaks and troughs for each note were used for all subsequent analyses. These numbers were used to produce figures depicting the patterns for each measurement through the scale. The data for the vibrato peaks and troughs and were then compared for the CQ, fundamental frequency, amplitude of the first five harmonics, and the harmonic number of the singer’s formant using a repeated measure ANOVAs.

RESULTS

The data were arrayed for analysis by dependent variable. The following sections provide the results for the variables CQ, fundamental frequency, harmonic 1, harmonic 2, harmonic 3, harmonic 4, harmonic 5, and the harmonic at which the singer formant was centered. In general, the measurements made at the peak of the vibrato cycle and those made at the trough exhibited the same pattern for the variables. Since there were slight differences that sometimes achieved statistical significance, the differences between them are included.

The variance within the measurements across the notes differed. These differences resulted in significant violations of Mauchly’s Test of Sphericity. The Greenhouse-Geisser correction of degrees of freedom was used correct for these differences. These corrections can be noted by degrees of freedom with decimal places in the reports of the ANOVAs.

Closing Quotient

Evaluation of the CQ data revealed patterns that differed from what occurs when speakers shift from modal to falsetto register. In those cases a rapid drop of CQ from the approximately

50% to approximately 35% marks the register transition. As shown in Figure 1, this group of trained singers generally exhibited a trend toward a lower CQ as the note became higher without a clear break between any two notes.

Figure 1. The mean closing quotient for the two measurement points across the octave scale.

Some of the singers exhibited patterns in the changes of their CQ as they sang up the octave. Two of the singers exhibited a notable CQ drop between notes: G06 between notes 4 and

5 and G04 between notes 6 and 7. In contrast, two of the singers exhibited a notable increase in their CQ as they sang the ascending octave: U01 and U02. Singer P02 exhibited a saucer shaped change in her CQ as she sang the ascending octave with a significant drop in CQ between notes 1 and 2. Finally, singer P03 sang the entire octave at a low CQ in the range, around .25. CQ values in this range are low in the spoken falsetto register. Her CQs were responsible for the wide standard deviations that can be seen in Figure 1.

The statistical analysis revealed a significant interaction between the point on the vibrato cycle and the note sung, with the means of the measurements taken at the peak of the vibrato cycle exhibiting a slight drop through the ascending octave and those taken at the trough of the

2 cycle being lower at the highest notes in the octave (F(3.54, 38.944)=2.895, p < .05, η p=.208).

The partial eta squared value indicates that the effect size of this interaction was moderately strong. The significant main effect findings for these two measures are consistent with the interaction noted above. The CQ differed significantly for both the point on the vibrato cycle 2 (F(1,11)=4.897, p < .05, η p=.308) and the note sung (F(2.749, 30.278)=3.054, p < .05,

2 η p=.217)

Fundamental Frequency

As would be expected, the fundamental frequency rose with each note in the octave scale and the measurements at the frequency peak of the vibrato cycle were higher than those at the trough. This pattern in the data can be seen in Figure 2. There was no significant interaction between the point of measurement and the notes. However, there were significant main effects for

2 the point of measurement (F(1,11)=34.988, p < .05, η p=.761) and the note sung (F(1.81,

2 19.909)=3.054, p < .05, η p=.217).

Figure 2. The mean fundamental frequencies for the singers at the two measurement points for the notes sung.

Amplitudes of the First Five Harmonics

As can be seen in Figure 3, the greatest energy tended to be in the first three harmonics,

particularly for the upper four notes. A rapid drop in energy occurred for the fourth harmonic after

the fourth note and for the fifth harmonic above the second note. At the first note there was little

average difference for the five harmonics. At the second note H3 was dominant as would be

expected for female singers in the chest register. At the fourth note the second harmonic became dominant for the remaining notes as would be expected for female singers in the mixed register.

The analyses for the individual harmonics follow.

Figure 3. The mean amplitudes for the singers at the first five harmonics across the notes of the octave scale.

Harmonic 1

All of the singers exhibited a similar pattern of H1 amplitude across the notes. For the highest note the amplitude of H1 approximated that of H2. The pattern was that the amplitude increased as the frequency of the note increased from approximately -25 dB at the first note to approximately -15 dB at the final note of the octave (See Figure 3). This result can be predicted as

H1 occurs at a higher frequency as the note increases and more closely approximated the frequency of the first formant or resonant peak of the vocal tract. As can be seen in Figure 4, no interaction occurred between the measurement points and notes, but significant main effects occurred for each. The point of measurement in the vibrato cycle was marked by greater

2 amplitudes at the peak of the vibrato cycle (F(1,11)=7.987, p < .05, η p=.421). As noted above the higher notes in the octave were sung with greater H1 amplitude (F(7,77)=136.661, p < .05,

2 η p=.926).

Figure 4. The mean H1 amplitudes for the singers at the vibrato peak and trough across the notes of the octave scale.

Harmonic 2

As for H1 all of the singers exhibited a similar pattern of H2 amplitude across the notes

with the amplitude increasing as the frequency of the note increased from approximately -25 dB at

the first note to approximately -12 dB at the final note of the octave. H2 closely approximates the

frequency of the first formant or resonant peak of the vocal tract for the upper four notes of the

octave. As can be seen in Figure 5, no interaction occurred between the measurement points and

notes, but significant main effects occurred for each. The point of measurement in the vibrato

cycle was marked by greater amplitudes at the peak of the vibrato cycle (F(1,11)=30.209, p < .05,

2 η p=.733). As noted above the higher notes in the octave were sung with greater H2 amplitude

2 (F(7,77)=60.101, p < .05, η p=.845).

Figure 5. The mean H2 amplitudes for the singers at the vibrato peak and trough across the notes of the octave scale.

Harmonic 3

The H3 amplitude increased as the frequency of the note increased from approximately -25 dB at the first note to approximately -14 dB at the fifth and sixth notes and then dropped to -18 to

-21 dB for the final note of the octave. The lowering of the H3 amplitude over the final notes of the octave made it so that no linear effect occurred for the note of the octave. As noted above, the

H3 amplitude was the strongest amplitude for the first three notes of the octave (See Figure 3). As can be seen in Figure 6, neither a significant interaction nor main effects occurred between the measurement points and notes.

Figure 5. The mean H3 amplitudes for the singers at the vibrato peak and trough across the notes of the octave scale.

Harmonic 4

The H4 amplitude across the notes held fairly steady across the first four notes at

approximately -25 dB and lowered to approximately -30 dB to -35 dB for the final three notes of

the octave. As can be seen in Figure 6, an interaction occurred between the measurement points

and notes with the vibrato peak measurements at greater amplitudes for the first three notes and

the vibrato troughs at greater amplitudes for the final four notes of the octave (F(7,77)=2.162, p <

2 .05, η p=.164). Given this pattern, no significant differences occurred for the point of measurement in the vibrato cycle. As noted above the highest three notes in the octave were sung with less H4 amplitude resulting in a significant amplitude difference across the notes (F(1.932,

2 21.255)=10.978, p < .05, η p=.500).

Figure 5. The mean H4 amplitudes for the singers at the vibrato peak and trough across the notes of the octave scale.

Harmonic 5

The H5 amplitude across the notes lowered from approximately -25 dB for the first two

notes to approximately -42 dB for the final note of the octave. As can be seen in Figure 7, an

interaction occurred between the measurement points and notes with the vibrato peak measurements at greater amplitudes for the first two notes and the vibrato troughs at greater

2 amplitudes for the remaining notes of the octave (F(7,77)=3.872, p < .05, η p=.260). The difference was greatest for notes three and four. Given this pattern, the vibrato troughs had

2 significantly higher amplitudes than the vibrato peaks (F(1, 11)=40.998, p < .05, η p=.788). As noted above the H5 amplitudes became steadily lower as the notes increased through the octave, resulting in a significant amplitude difference across the notes (F(2.599, 28.585)=24.493, p < .05,

2 η p=.260).

Figure 7. The mean H5 amplitudes for the singers at the vibrato peak and trough across the notes of the octave scale.

Harmonic of the Singer’s Formant

The number of the harmonic at which the singer’s formant occurred lowered from the 13th and 14th harmonic for the lowest note in the octave to 7th and 8th harmonic for the highest note.

That the harmonic will become lower as frequency increases is natural, since the harmonics are multiples of the fundamental frequency. Since the frequency range of the singer’s formant remains consistent across notes, it would be expected that the number of the harmonic at the singer’s formant for the highest note in the octave scale would be approximately one half of the number of the harmonic at the singer’s formant for the lowest note. As can be seen in Figure 8, the vibrato trough measurements consistently higher mean harmonic numbers than did the vibrato peaks

2 across the notes of the octave (F(1, 11)=55.548, p < .05, η p=.835). As noted above the harmonic of the singer formant became steadily lower as the notes increased through the octave, resulting in

2 a significant amplitude difference across the notes (F(7, 77)=440.128, p < .05, η p=.976).

Figure 8. The mean formant for the singer formant at the vibrato peak and trough across the notes of the octave scale.

DISCUSSION

Because creation of vibrato requires changes in the larynx, measurements were taken at the vibrato peaks and troughs to evaluate any differences among the dependent variables. The data showed that measurements taken at the vibrato peaks and troughs had similar patterns. Even though the overall patterns were similar, significant differences often occurred between these sets of measurements. These differences occurred for the measurements of all the dependent measures:

CQ, harmonic amplitudes, and the harmonic number for the singer’s formant. The patterns for these variables are reported below.

Although it was hypothesized that the singers would exhibit a marked drop in CQ from the lowest note in the octave to the highest, the CQ dropped gradually with ascension through the notes of the octave. The CQ of the typical speaking voice rapidly drops when making the

transition from modal to falsetto; however, singers strive to make the transition more gradual

(Miller & Schutte 2005). The singers in the present study achieved this gradual drop in average CQ and maintained a CQ in the range of the chest register, between 40 and 50%. As a group these singers exhibited CQs that should lead to a perceptually smooth primo passaggio.

Miller and Schutte (2005) described that singers who are belting have a higher CQ much

like the chest register when they sing higher notes, which can be a possible explanation for the

singers who exhibited rising CQ levels at the highest frequencies in the octave. A few singers

exhibited patterns that differed from what most of the singers did with two of the graduate singers

exhibiting a drop consistent with a speaker’s registers transition. It should be noted that one of the

professional singers reported by Miller and Schutte (2005) also exhibited this pattern. From the

current data it appears that the predominant pattern for CQ across the primo passaggio for trained

female singers is a gradual lowering within the range for the chest voice.

The CQs were consistently a few percent higher at the peaks than the troughs, which

created a significant difference between the two measurement points. The increased level of the

cricothyroid muscle activity that occurs at vibrato peaks (Titze, Solomon, Luschei, & Hirano,

1994) would increase the stiffness of the vocal folds. This increased stiffness of the vocal folds

would slightly increase the CQ so that additional subglottal pressure could build.

As expected, the third harmonic was dominant at the lower notes. The singers exhibited an

amplitude increase followed by the amplitude falling in the higher notes, which supports the fact

that the third harmonic is dominant for the lower notes. This pattern in the third harmonic

supports the previous claim that the register transition occurs near the third and fourth notes; above transition the third and higher harmonics had smaller amplitudes. When the singers make

the transition from chest to mixed register there is drop in subglottal pressure (Miller & Schutte,

2005) and the frequencies of the third and higher harmonics are higher than the second formant.

These changes could explain the drop in amplitude among these harmonics.

There is a pattern of the overall harmonics in which the greatest concentration of energy is

in the first three harmonics, as to be expected. A possible explanation for the concentration of

energy in the first three harmonics is that these harmonics are more closely related to the first and

second formants than the other harmonics are to the third formant. In the production of the vowel

[a:] the first and second formants are close to each other, which results in a large gap between the second and third formants. The fourth and fifth harmonics fall in this gap between the second and third formants which may mark the difference between the chest and mixed registers. According to

Neumann, Schunda, Hoth, and Euler (2005) the drop in the amplitude of the fourth harmonic occurs at the transition for back vowels, such as [a:], because prior to the transition the fourth harmonic is supported by the second formant but the transition leads to the second formant to switch to supporting the third harmonic. The fifth harmonic may experience this as well.

Titze (2008) stated that when the harmonics approach any of the formants vocal instabilities occur. This instability may have increased the amplitude differences between the measure taken at the peaks and troughs of the vibrato for the first three harmonics. Interestingly, the second harmonic was the most dominant in the fourth note which was approximately where the singers made a register transition, which is supported by Miller and Schutte (2005). This result is to be expected though because of the singer performing in the mixed register. The vocal instabilities that accompany this harmonic approaching the first formant could possibly be linked to the register transition. Given that the mixed register is not supported by either glottal or vocal tract source exclusively, an equal and sustainable combination of the two sources could be difficult to achieve.

The singers in this investigation produced singer’s formants in a pattern that would be expected of singing through an octave. The singer’s harmonic begins high and then drops to a lower harmonic because of the nature of what the singer’s formant is. Given that this formant occurs between 2500 and 3000 Hz for all singers, as the fundamental frequency increases the harmonic decreases because it is the multiple needed for the fundamental frequency to be in the range of the formant. Since the singers who participated in this study produce expected and normal, results for this measurement the reliability of the results is increased.

Some issues occurred for measurements used in this study. The delay of the audio signal relative to the EGG signal would be more consistent across notes if a headset microphone was used. Although the participants were placed a specific distance from the microphone, some of the singers would lean back or forward while singing which altered the delay between the audio and

EGG signals. The measurement of the EGG signal was affected by the setting of the closing level.

Many of the signals did not have a clear transition point for setting the closing level. Thus some

CQ measurement errors may have occurred.

Although some of the results of this study were as expected, others bring questions to light.

In the context of the vibrato cycle, the peak consistently produced higher measurements for the

CQ, fundamental frequency, and the first, second, and third harmonics. The fourth and fifth harmonics and the singer’s formant produced higher measurements at the troughs of the vibrato cycle. An explanation to this phenomenon has the potential to reveal more insights to a perceptually smooth primo passaggio. References

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