Vocal initiation: acoustic and aerodynamic investigations of normal subjects

Whisper and Phonation: Aerodynamic Comparisons Across Adduction and Loudness

INTRODUCTION

Whisper is known to be produced by different speakers differently, especially with respect to glottal configuration that influences glottal aerodynamics. Differences in whisper production and phonation types imply important linguistic information in many languages, are identified in vocal pathologies, are used to communicate mood and emotion, and are used in vocal performance.

OBJECTIVE

The present study focused on investigating the aerodynamic differences between whisper and phonation at different loudness and adduction levels.

METHODS

Three men and five women between 20 and 40 years of age participated in the study. Smooth syllable strings of the syllable /baep:/ were whispered and phonated at three different loudness levels (soft, medium, and loud) and three voice qualities (breathy, normal, and pressed). The voice qualities are associated with different adduction levels. This resulted in 18 treatment combinations (three adduction levels × three loudness levels × two sexes).

RESULTS

A regression analysis was performed using a PROC MIXED procedure with SAS statistical software. Under similar production conditions, subglottal pressure was significantly lower in whisper than in phonation in 10 of 18 combinations, mean glottal airflow was significantly higher in whisper than in phonation in 13 of 18 combinations, and flow resistance was significantly lower in whisper than in phonation in 14 of 18 combinations, with the female subjects demonstrating these trends more frequently than the male subjects do. Of importance, in general, compared with phonation under similar production conditions, whisper is not always accompanied by lower subglottal pressure and higher airflows.

CONCLUSION

Results from this study suggest that the typical finding of lower subglottal pressure, higher glottal airflow, and decreased flow resistance in whisper compared with phonation cannot be generalized to all individuals and depends on the "whisper type." The nine basic production conditions (three loudness levels and three adduction levels) resulted in data that may help explain the wide range of variation of whisper production reported in earlier studies.

Relationship Between Acoustic Voice Onset and Offset and Selected Instances of Oscillatory Onset and Offset in Young Healthy Men and Women

OBJECTIVE

This study aimed to investigate the relationship between (1) onset of the acoustic signal (X_1a) and prephonatory phases associated with oscillatory onset and (2) offset of the acoustic signal (X_2a) with the postphonatory events associated with oscillatory offset across vocally healthy adults.

SUBJECTS AND METHODS

High-speed videoendoscopy was captured simultaneously with the acoustic signal during repeated production of /hi.hi.hi/ at typical pitch and loudness from 56 vocally healthy adults (aged 20-42 years; 21 men, 35 women). The relationships between the acoustic sound pressure signal and oscillatory onset and offset events from the glottal area waveforms (GAWs) were statistically investigated using a multivariate linear regression analysis.

RESULTS

The X_1a is a significant predictor of the onset of first oscillatory motion (X_1g) and onset of sustained oscillations (X_2g). X_1a as well as gender are significant predictors of the first medial contact of the vocal folds (X_1.5g). The X_2a is a significant predictor of the first instance of oscillatory offset (X_3g), first instance of incomplete glottal closure (X_3.5g), and complete cessation of (vocal fold) oscillatory motion (X_4g).

CONCLUSIONS

The acoustic signal onset is closely related to the X_1.5g, but the latency between these events is longer for women compared to men. The X_2a occurs immediately after incomplete glottal adduction. The emerging normative group latencies between the onset and offset of the acoustic and the GAW from this study appear promising for future investigations.

Effects of Volume, Pitch, and Phonation Type on Oscillation Initiation and Termination Phases Investigated With High-speed Videoendoscopy

OBJECTIVES

This study aimed to investigate the effects of varying volume, pitch, and phonation types on the initiation and termination phases of vocal fold oscillation using high-speed digital videoendoscopy. Specifically, it addressed the effects of the variation of volume, pitch, and phonation type (normal, pressed, and breathy) on the transient duration of the vibrating glottal length (length transient duration, T_len), the transient duration of the glottal area waveform (area transient duration, T_area), the time offset between the beginning (or the end) of the full-length vibration and the full-amplitude vibration, T_Δ, and the variation of the fundamental frequency during the vocal fold oscillation initiation and termination segments (pitch instability, %PI).

METHODS

A female subject with no voice problem produced voices with varying pitch and loudness, including comfortable pitch and comfortable loudness, normal pitch loud, high pitch and comfortable loudness, and high pitch and loud. Breathy and pressed phonations were also recorded. Each of the six phonation types was recorded six times, which resulted in 72 transient segments (each recording included both initiation and termination phases). Mixed model statistical analyses were employed to the five objective high-speed digital videoendoscopy parameters.

RESULTS

Preliminary findings demonstrated significant findings for voice type effects for the length and area transient durations for the oscillation initiation segment but not for the oscillation termination segment.

CONCLUSIONS

This study demonstrates that voice types appear to influence vibration initiation patterns more than the vibration termination patterns.

Dynamics of phonatory posturing at phonation onset

INTRODUCTION

In speech and singing, the intrinsic laryngeal muscles set the prephonatory posture prior to the onset of phonation. The timing and shape of the prephonatory glottal posture can directly affect the resulting phonation type. We investigated the dynamics of human laryngeal phonatory posturing.

METHODS

Onset of vocal fold adduction to phonation was observed in 27 normal subjects using high-speed video recording. Subjects were asked to utter a variety of phonation types (modal, breathy, pressed, /i/ following sniff). Digital videokymography with concurrent acoustic signal was analyzed to assess the timing of the following: onset of adduction to final phonatory posture (FPT), phonation onset time (POT), and phonatory posture time (PPT). Final phonatory posture time was determined as the moment at which the laryngeal configuration used in phonation was first achieved.

RESULTS

Thirty-three audiovisual recordings met inclusion criteria. Average FPT, PPT, and POT were as follows: 303, 106, and 409 ms for modal; 430, 104, and 534 ms for breathy; 483, 213, and 696 ms for pressed; and 278, 98, and 376 ms for sniff-/i/. The following posturing features were observed: 1) pressed phonation: increased speed of closure just prior to final posture, complete glottal closure, and increased supraglottic hyperactivity; and 2) breathy phonation: decreased speed of closure prior to final posture, increased posterior glottal gap, and increased midmembranous gap.

CONCLUSIONS

Phonation onset latency was shortest for modal and longest for pressed voice. These findings are likely explained by glottal resistance and subglottal pressure requirements.

LEVEL OF EVIDENCE

NA. Laryngoscope, 126:1837-1843, 2016.

A Spatiotemporal Approach to the Objective Analysis of Initiation and Termination of Vocal-fold Oscillation With High-speed Videoendoscopy

High-speed videoendoscopy excels in the ability to observe the vocal-fold oscillatory patterns during voice initiation and termination. The initial and most critical step in the analysis of these transient regions is to identify the locations of these transient periods, that is, determining when the vocal-fold oscillation is absent and when the oscillation has reached its steady-state behavior. The latter is more challenging as the "steady" oscillation during sustained phonation is not truly steady and is expected to vary over time. This variation may cause unreliable identification of the transient periods, possibly resulting in less accurate or less reliable parameter measurements. An oscillation feature that is relatively consistent in the steady state is the glottal length, that is, the extent of the oscillation along vocal folds. This paper proposes an autonomous algorithm to estimate the vocal-fold oscillation length and its use to detect four transient events: oscillation onset and offset, and attainment and loss of full-length oscillation. The detected event markers are intended to be used to improve the transient parameter measurements. The autonomous algorithm manipulates the set of glottal width waveforms spatiotemporally to estimate the oscillation length. Examples with in vivo high-speed videoendoscopy recordings of both normal and pathological cases are included to show the efficacy of the proposed algorithm to identify the transient markers.

Effect of Voice Onset Type on Vocal Attack Time

Vocal attack time (VAT) is the time lag between the growth of sound pressure (SP) and electroglottographic (EGG) signals at vocal initiation. The characteristics of voice initiation are associated with issues of vocal hygiene, efficiency, and quality. Vocal onsets have commonly been qualitatively characterized into three types: hard, simultaneous, and breathy. This study examines the effect of voice onset type on VAT values in normal speakers. SP and EGG recordings were obtained for 55 female and 57 male subjects while producing multiple tokens of three tasks (sustained /ɑ/ and "always" as unaspirated onsets, and "hallways" as an aspirated onset). Results revealed a significant effect of onset type on VAT, with the mean VAT for the "hallways" (aspirated) task greater than the mean VAT for the sustained /ɑ/ and "always" (unaspirated) tasks. There was no significant VAT difference between the sustained /ɑ/ and "always" tasks. Findings confirm the sensitivity of the VAT measure to vocal onset type and suggest its potential application as an objective and quantitative clinical measure of the type of vocal onset.

Abrupt laryngeal engagement during stop plosive-vowel transitions in children with repaired cleft palate and adequate velopharyngeal closure: aerodynamic and sound pressure level evidence

OBJECTIVE

To determine whether children with repaired cleft palate and adequate velopharyngeal closure exhibit abrupt laryngeal engagement during stop plosive-vowel transitions as compared with children without cleft palate.

DESIGN

A prospective group design was used with convenience sampling of patients at a university craniofacial center.

PARTICIPANTS

PARTICIPANTS were 25 children (15 boys, 10 girls) with repaired cleft palate (mean age = 10.9 years, standard deviation = 1.5 years) and 20 children (10 boys, 10 girls) without cleft palate (mean age = 10.8 years, standard deviation = 1.8 years). All children with cleft palate had adequate velopharyngeal closure as determined by aerodynamic testing.

MAIN OUTCOME MEASURES

(1) Peak oral airflow was determined during the release of /t/ in the word "two" during a counting task. (2) An index of laryngeal engagement defined as the ratio of the maximum oral airflow declination to peak oral airflow was calculated during the release of /t/. (3) Sound pressure level was determined during the vowel of the word "two."

RESULTS

Children with cleft palate exhibited significantly more negative laryngeal engagement ratios (i.e., more abrupt adduction) (P = .002) and greater sound pressure level (P = .049) than controls. There was a significant negative relationship between laryngeal engagement and sound pressure level for all children (r = -.428, P = .003).

CONCLUSIONS

Children with repaired cleft palate and adequate velopharyngeal function appear to use a strategy of abrupt laryngeal adduction during stop plosive-vowel transitions. This strategy-perhaps learned even prior to palate surgery-may help to achieve either adequate sound pressure level and/or velopharyngeal closure.

Effect of fundamental frequency at voice onset on vocal attack time

OBJECTIVE

To examine vocal attack time (VAT) values associated with the production of low, mid, and high rates of vocal fold vibration in normal speakers.

STUDY DESIGN

Sound pressure (SP) and electroglottographic (EGG) recordings were obtained for eight female and five male subjects while producing multiple tokens of the sustained vowels /ɑ/, /i/, and /u/ at comfortable loudness and at mid, low (-3 semitones), and high (+6 semitones) rates of vocal fold vibration.

METHODS

Generalized sinusoidal models of the SP and EGG signals were computed to compare rates of amplitude change. VAT was computed from the time lag of the cross-correlation function.

RESULTS

Adjusted mean VAT for the high frequency condition was smaller than the adjusted mean VAT values for the low- and mid-frequency conditions. There was no significant difference between the mid and low frequency conditions.

CONCLUSIONS

Findings reveal an association of the VAT measure with increases in vocal fold tension associated with the production of high rates of vocal fold vibration.

Vocal release time: a quantification of vocal offset

OBJECTIVE

To determine the vocal release time (VRT) for linguistically unconstrained voice offsets in a healthy young adult population.

STUDY DESIGN

Sound pressure (SP) and electroglottographic (EGG) recordings were obtained for 57 female and 55 male subjects while producing multiple tokens of three tasks (sustained /ɑ:/, "always," and "hallways") at comfortable pitch and loudness.

METHODS

SP and EGG signals were digitally time reversed and generalized sinusoidal models of the SP and EGG signals were obtained to compare rates of amplitude change. VRT was computed from the time lag of the cross-correlation function.

RESULTS

Adjusted mean VRT values were significantly greater for females than for males. There was no systematic effect of age on VRT. However, 25-29-year old and >40 year old females showed shorter VRT values than the youngest female age group.

CONCLUSIONS

Normative data are presented for a new measure of the duration of vocal offset, VRT. Acquisition of this measure requires little user intervention, thereby minimizing effects of subjective decision making. Comparison with previously reported vocal attack time (VAT) values for the same population suggests phenomenological differences between linguistically and physiologically constrained voice onsets and unconstrained voice offsets.

Validation of a glottographic measure of vocal attack

The speed with which the vocal folds adduct to the midline is considered an important variable in the etiology of some voice disorders and may also be a meaningful indicator of central or peripheral neural dysfunction. It is proposed that the time lag between the rise of the sound pressure (SP) and electroglottographic (EGG) signals, measured at the onset of phonation, provides a useful index of vocal attack time. This report describes the experimental validation of this measure, whereby the SP and EGG signals were recorded synchronously with high-speed videoendoscopy, from which a digital kymogram was generated. It is shown that, after appropriate signal processing, the intersignal time delay provides a potentially useful measure that varies with vocal attack characteristics. The proposed method calls for no invasive procedures and relies on signals that are routinely obtained in most clinical settings. Unlike acoustic "rise time" measures of voice onset, the glottographic measure involves no operator intervention, requires no arbitrary decisions about measurement points, and may be accomplished quickly and automatically on any personal computer.

Incidence of supraglottic activity in males and females: a preliminary report

Supraglottic activity was rated from flexible endoscopic video recordings of subjects with normal laryngeal structure and function as they sustained vowels and repeated syllables and sentences. Judges rated these recordings for false vocal fold (FVF) adduction and anterior-to-posterior (A-P) compression at the initiation of the speech task, throughout the whole speech task (static supraglottic activity), and as brief individual adductions within a speech task (dynamic supraglottic activity). Significant differences in A-P (p < 0.0003) and FVF (p < 0.0000001) compression were found between tasks. Dynamic FVF activity was associated with glottal stops. Static A-P and FVF activities were present in males significantly more (p < 0.0001) than females. FVF activity associated with speech initiation was found in females significantly more (p = 0.0256) than males. Supraglottic activity plays a role in normal speech production, and should not necessarily be considered suggestive of a voice use pattern with excessive muscle tension.

The effects of fluency-evoking conditions on voicing onset types in persons who do and do not stutter

Voicing onset changes between control conditions and three fluency-evoking conditions (choral reading [CHORAL], delayed auditory feedback [DAF], and noise [NOISE]) were studied in 12 persons who do not stutter and 10 who do stutter. Voicing onsets were distinguished physiologically using airflow prior to voicing, with zero airflow prevoicing categorized as hard and the rest as breathy. Persons who stutter were more fluent under all fluency-evoking conditions than control conditions. Speaking under fluency-evoking conditions did not significantly increase the overall proportion of breathy onsets from control conditions for either group. However, looking only at hard onsets in the control condition, we found that both groups changed significantly more to breathy (p = 0.001) under CHORAL and NOISE. In persons who stutter, onset type was not associated with whether a word was produced fluently or dysfluently in the control condition. Also, no relationship was found between onsets changing to breathy under fluency-evoking conditions and onsets changing to fluent. The results suggest that although fluency-evoking conditions can modify some voicing onset behaviors, these modifications do not relate to improvements in fluency.

Acoustic measurement of voice quality in central dysphonia

Speech samples of 14 male and 10 female patients with central dysphonia were examined. Eighteen patients had suffered a severe closed head trauma and the remaining six patients had experienced cerebrovascular accident (CVA). Several parameters were developed in order to find acoustic correlates for three major pathologic voice qualities in central dysphonia. The well know jitter parameter, fundamental period perturbation (PP), was adapted for our purposes and proved to be a good measure for rough voices, though the patients revealed less jitter than in peripheral dysphonia. The vocal onset parameter, time lag of preexhalation (Tb), and the spectral parameter, spectral energy above 5 KHz (A5), classified the breathy voices. Most of the tense voices could be detected by the spectral parameters, spectral energy in the 1-5 KHz range (A1), and variance of spectral energy above 5 KHz (V5). The successful classification of these voice qualities allowed the description of compound pathologic voice types in central dysphonia.

Consistency of laryngeal airway resistance in adult women

Fifteen young adult women performed a noninvasive clinical technique for measurement of laryngeal airway resistance (Rlaw) during syllable (consonant plus vowel) production. The data were recorded from oscillographic records of translaryngeal air pressure (Ptr - Pph) and translaryngeal airflow (Vt1) over 2 days, during two time periods on each day. The overall mean Rlaw for the experimental sessions was 38.3 cmH2O/LPS (SD = 9.24). No significant differences were found within or between days or time of day for the subjects. The obtained values were similar to mean values obtained for men in a previous study (Smitheran and Hixon, 1981). Single subject phonation data were also gathered during a controlled intensity condition. The Rlaw range and standard deviation figures decreased significantly from the uncontrolled condition during syllable productions to the midrange intensity (75 dB SPL). This finding suggests that control of intensity is an important variable to consider during clinical sampling. The measurement procedure shows promise clinically as an index of actual laryngeal resistance under selected control conditions and in relation to simultaneous comparison of patient strategies used to regulate translaryngeal pressure and airflow.