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Current speech motor control models suggest that speech movements are executed through a combination of feedforward control and feedback control (see Parrell et al., 2019, for a review). Specifically, feedforward [...], Purpose: Speech production requires the combined efforts of feedforward control and feedback control subsystems. The primary purpose of this study is to explore whether the relative weighting of auditory feedback control is different between the first language (L1) and the second language (L2) production for late bilinguals. The authors also make an exploratory investigation into how bilinguals' speech fluency and speech perception relate to their auditory feedback control. Method: Twenty Chinese-English bilinguals named Chinese or English bisyllabic words, while being exposed to 30- or 60-dB unexpected brief masking noise. Variables of language (L1 or L2) and noise condition (quiet, weak noise, or strong noise) were manipulated in the experiment. L1 and L2 speech fluency tests and an L2 perception test were also included to measure bilinguals' speech fluency and auditory acuity. Results: Peak intensity analyses indicated that the intensity increases in the weak noise and strong noise conditions were larger in L2-English than L1-Chinese production. Intensity contour analysis showed that the intensity increases in both languages had an onset around 80-140 ms, a peak around 220-250 ms, and persisted till 400 ms post vocalization onset. Correlation analyses also revealed that poorer speech fluency or L2 auditory acuity was associated with larger Lombard effect. Conclusions: For late bilinguals, the reliance on auditory feedback control is heavier in L2 than in L1 production. We empirically supported a relation between speech fluency and the relative weighting of auditory feedback control, and provided the first evidence for the production-perception link in L2 speech motor control.

The voice physiology literature supports the notion that healthy 'normal' voice production results from the coordinated activity of three component subsystems: respiration, phonation, and resonance (Isshiki, 1964; Kent, 1997; Stemple, [...], Purpose: Normative data for many objective voice measures are routinely used in clinical voice assessment; however, normative data reflect vocal output, but not vocalization process. The underlying physiologic processes of healthy phonation have been shown to be nonlinear and thus are likely different across individuals. Dynamic systems theory postulates that performance behaviors emerge from the nonlinear interplay of multiple physiologic components and that certain patterns are preferred and loosely governed by the interactions of physiology, task, and environment. The purpose of this study was to descriptively characterize the interactive nature of the vocalization subsystem triad in subjects with healthy voices and to determine if differing subgroups could be delineated to better understand how healthy voicing is physiologically generated. Method: Respiratory kinematic, aerodynamic, and acoustic formant data were obtained from 29 individuals with healthy voices (21 female and eight male). Multivariate analyses were used to descriptively characterize the interactions among the subsystems that contributed to healthy voicing. Results: Group data revealed representative measures of the 3 subsystems to be generally within the boundaries of established normative data. Despite this, 3 distinct clusters were delineated that represented 3 subgroups of individuals with differing subsystem patterning. Seven of the 9 measured variables in this study were found to be significantly different across at least 1 of the 3 subgroups indicating differing physiologic processes across individuals. Conclusion: Vocal output in healthy individuals appears to be generated by distinct and preferred physiologic processes that were represented by 3 subgroups indicating that the process of vocalization is different among individuals, but not entirely idiosyncratic. Possibilities for these differences are explored using the framework of dynamic systems theory and the dynamics of emergent behaviors. A revised physiologic model of phonation that accounts for differences within and among the vocalization subsystems is described. Supplemental Material: https://doi.org/10.23641/ asha.7616462

The ventricular folds, also called false vocal folds or vestibular folds, are two laryngeal structures located above and in the vicinity of the vocal folds. As illustrated in Figure 1a, [...], Purpose: In this study, the authors aimed (a) to provide a classification of the ventricular-fold dynamics during voicing, (b) to study the aerodynamic impact of these motions on vocal-fold vibrations, and (c) to assess whether ventricular-fold oscillations could be sustained by aerodynamic coupling with the vocal folds. Method: A 72-sample database of vocal gestures accompanying different acoustical events comprised high-speed cinematographic, audio, and electroglottographic recordings of 5 subjects. Combining the physiological correlates with a theoretical model of phonation, the vocal-ventricular aerodynamic interactions were investigated. Results: A ventricular-fold motion is found during (de)crescendos, shout, throat singing, yodel, growls, and glides with transitions between registers. Three main types of dynamics are identified: slow nonoscillatory motion and fast oscillatory motion with aperiodical or periodical vibrations. These patterns accompany a change in voice quality, pitch, and/or intensity. Alterations of glottal-oscillatory amplitude, frequency, and contact were predicted. It is shown that a ventricular oscillation can be initiated and sustained by aerodynamic coupling with the vocal folds. Conclusions: Vocal-ventricular aerodynamic interactions can alter, enhance, or suppress vocal-fold vibrations or leave them unchanged, depending on the ventricular-fold dynamics involved. Depending on its variation in time, a similar level of ventricular-fold adduction impacts the glottal vibratory magnitude and contact much differently. Keywords: voice, ventricular folds, aerodynamics, high-speed cinematography, phonation modeling

Paralysis of the superior laryngeal nerve (SLN) impairs voice production by decreasing stimulation to the cricothyroid (CT) muscle, thereby preventing normal vocal fold elongation. Superior laryngeal nerve paralysis (SLNP) often [...], Purpose: To model tension asymmetry caused by superior laryngeal nerve paralysis (SLNP) in excised larynges and apply perturbation, nonlinear dynamic, and aerodynamic analyses. Method: SLNP was modeled in 8 excised larynges using sutures and weights to mimic cricothyroid (CT) muscle function. Weights were removed from one side to create tension asymmetry, mimicking unilateral SLNP. Two sets of weights were used, 1 light and 1 heavy. Five conditions were evaluated: (a) no tension, (b) symmetrical light tension, (c) asymmetrical light tension, (d) symmetrical heavy tension, and (e) asymmetrical heavy tension. Results: Perturbation parameters were not significantly different across conditions: percent jitter, [chi square](4) = 3.70, p = .451; percent shimmer, F(4) = 0.95, p = .321. In addition, many measurements were invalid (error values >10). Second-order entropy was significantly different across conditions, F(4) = 5.432, p = .002, whereas correlation dimension was not, F(4) = 0.99, p = .428. Validity of these nonlineardynamic parameters was demonstrated by low standard deviations. Phonation threshold pressure, [chi square] (4) = 22.50, p < .001, and power, [chi square] (4) = 9.50, p = .05, differed significantly across conditions, whereas phonation threshold flow did not, [chi square] (4) = 4.08, p = .396. Conclusions: Nonlinear dynamic analysis differentiated between symmetrical and asymmetrical tension conditions, whereas traditional perturbation analysis was less useful in characterizing type 2 or 3 vocal signals. Supplementing acoustic with aerodynamic parameters may help distinguish among laryngeal disorders of neuromuscular origin. Key Words: superior laryngeal nerve paralysis, tension asymmetry, nonlinear dynamic analysis, acoustic analysis, aerodynamic analysis

Roughness is an important dimension of dysphonic voice quality and may be defined as the psycho1 % acoustic impression of irregularity of vocal fold vibrations (Hirano, 1981). Perceptual evaluation of [...], Purpose: Perceptual estimates of voice quality obtained using rating scales are subject to contextual biases that influence how individuals assign numbers to estimate the magnitude of vocal quality. Because rating scales are commonly used in clinical settings, assessments of voice quality are also subject to the limitations of these scales. Instead, a matching task can be used to obtain objective measures of voice quality, thereby facilitating model development and tools for clinical use. Method: Twenty-seven individuals participated in a rating task or at least 1 of 3 matching tests (named after their modulation functions: SINE, SQUARE, POWER) to quantify the degree of roughness in dysphonic voice stimuli. Participants evaluated the roughness of 34 voice samples using an amplitude-modulated complex carrier. Results: The matching thresholds were highly correlated with the ratings estimates. Reliability of thresholds did not significantly differ across tasks, but linear regressions showed that the POWER test resulted in larger perceptual distances. Conclusions: A matching task can be used to obtain reliable estimates of roughness in dysphonic voices. The POWER comparison is recommended because the variability in matching thresholds across the range of roughness was evenly distributed, and the perceptual distances between stimuli were maximized. Key Words: voice quality, roughness, rating scale, matching, amplitude modulation

Wet vocal quality (WVQ) is a widely used term describing a type of voice abnormality that is considered an important clinical sign of dysphagia. It is presumed to be perceptually [...], Purpose: In the present study, the authors investigated the association between wet vocal quality (WVQ) and prandial material in the larynx during phonation. The presence of such material is indicative of oropharyngeal dysphagia and results from entry of material into the laryngeal vestibule during swallowing. The primary aim of the study was to determine whether clinicians reliably perceive WVQ during phonation when prandial material is in the larynx. Method: Seventy-eight subjects underwent videofluoroscopic swallow study, and simultaneous recording of time-linked videofluoroscopic and acoustic data was conducted during postswallow phonation. Experienced dysphagia clinicians then rated randomized audio samples for presence or absence of WVQ. Results: WVQ is not reliably perceived by clinicians when material is present in the larynx in the region of the glottis during phonation, and there is a high degree of interrater variability for perceptual judgments of wetness. Conclusions: Material in the larynx during phonation may result in multiple voice quality percepts, and even experienced clinicians may not be adept at identifying the perceptual consequences of this. Observation of laryngeal physiology during voicing when material is in the larynx using vocal tract imaging can improve reliability in the identification of wet vocal quality.

Generally, there is a significant relationship between some acoustic measures ([F.sub.0] and formant parameters) and the body size of speakers; however, data become less clear when age and sex variables are controlled. To date, no other vocal parameter apart from [F.sub.0] has been studied in relation to body size. In the present study, correlations between a set of 27 parameters of the Multi-dimensional Voice Program (Kay Elemetrics Corp.) and 4 body measures were obtained from 134 speakers of both sexes belonging to one age group (20-29 years). Correlations within sex groups were null or very weak, and all significant coefficients were below .35.

This paper aims at providing new objective parameters and plots, easily understandable and usable by clinicians and logopaedicians, in order to assess voice quality recovering after vocal fold surgery. The proposed software tool performs presurgical and postsurgical comparison of main voice characteristics (fundamental frequency, noise, formants) by means of robust analysis tools, specifically devoted to deal with highly degraded speech signals as those under study. Specifically, we address the problem of quantifying voice quality, before and after medialization thyroplasty, for patients affected by glottis incompetence. Functional evaluation after thyroplastic medialization is commonly based on several approaches: videolaryngostroboscopy (VLS), for morphological aspects evaluation, GRBAS scale and Voice Handicap Index (VHI), relative to perceptive and subjective voice analysis respectively, and Multi-Dimensional Voice Program (MDVP), that provides objective acoustic parameters. While GRBAS has the drawback to entirely rely on perceptive evaluation of trained professionals, MDVP often fails in performing analysis of highly degraded signals, thus preventing from presurgical/postsurgical comparison in such cases. On the contrary, the new tool, being capable to deal with severely corrupted signals, always allows a complete objective analysis. The new parameters are compared to scores obtained with the GRBAS scale and to some MDVP parameters, suitably modified, showing good correlation with them. Hence, the new tool could successfully replace or integrate existing ones. With the proposed approach, deeper insight into voice recovering and its possible changes after surgery can thus be obtained and easily evaluated by the clinician. Index Terms--Acoustic signal analysis, formants, fundamental frequency, noise measurements, voice quality.

Alterations in the vibratory properties of the vocal folds give rise to acoustically and perceptually distinct vocal qualities (or registers) (Daniloff, Shuckers, & Feth, 1980). Vocal fry is one such [...], Two unique characteristics of vocal fry register are the occurrence of multiple opening and closing phases occurring within one vibratory cycle and a similar vocal fundamental frequency ([F.sub.0]) between women and men. The present study tested the hypothesis that significant differences in glottal cycle symmetry exist between women and men during modal phonation, with no significant differences during vocal fry phonation. Consistent with previous studies of modal phonation, it was also hypothesized that a vowel effect would be apparent during vocal fry phonation. Five women and 5 men sustained modal and vocal fry phonations in four vowel contexts (/a, ae, u, i/). Vocal [F.sub.0], duration of opening and closing phase, and contact symmetry (speed quotient) were derived from electroglottographic (EGG) waveforms. Both female and male speakers demonstrated significantly higher SQ values in vocal fry register than in their modal register, indicating a longer opening-phase duration per glottal cycle. Women demonstrated a significantly greater increase in SQ during vocal fry phonations than men, indicating greater asymmetry between opening and closing durations. The results confirmed that gender differences in vocal fold contact behavior not only exist during modal register but also during vocal fry register. No vowel effects on vocal fold contact behavior as inferred using the SQ measure were found for either modal or vocal fry registers. Possible contributing factors to multiple opening and closing phases occurring within a vibratory cycle are discussed. KEY WORDS: electroglottograph, gender, modal register, vocal fry, vocal fold contact

Summary: Pitch-synchronous changes in the anterior cricothyroid (CT) space were registered with ultrasonography (USG) for ten healthy subjects (5 males, 5 females) during the production of musical fifths throughout the [...]

Summary: Oral breathing superficially dehydrates the airway lumen by decreasing the depth of the sol layer in humans and animals. Conversely, nasal breathing can increase the humidity of inspired air. [...]

Hydration has long been a source of interest in basic and clinical voice science. In this study, we address questions about the mechanisms by which dehydration produces known changes in [...], Four vocally untrained healthy adults, 2 men and 2 women, completed the study. A double-blind placebo-controlled approach was used to administer three treatments to each participant on separate days. Drugs treatments involved a single 60-mg dose of a diuretic, Lasix (LA), on one day, and a single 50-mg dose of an oral antihistamine, diphenhydramine hydrochloride (DH), on another day. A third day involved the administration of a placebo, sugar pills (SP). Critical posttreatment measures were weight (kg), which estimated systemic dehydration, saliva viscosity (centipoise), which estimated secretion dehydration, and phonation threshold pressure (PTP, in cm [H.sub.2]O), at high pitches, which indicated pulmonary drive for phonation. The central experimental question was: Does systemic dehydration, or secretory dehydration, or both, mediate increases in PTP that are known to occur following dehydration treatments? The results showed that LA induced systemic dehydration, as shown by a decrease in total body mass of about 1%. Weight losses were seen during a 1- to 4-hour block following drug administration and persisted for at least 8 hours thereafter. PTPs also increased in that condition, about 23% relative to baseline, but only several hours after whole-body dehydration was initially seen (5-12 hours after drug administration). In contrast, no evidence was seen that DH accomplished either secretory dehydration or PTP shifts. The results indicate that systemic dehydration can mediate PTP increases. The influence of secretory dehydration on PTP is unclear. KEY WORDS: voice, dehydration, viscosity, phonation threshold pressure

Models of tongue motion and deformation differ widely depending on the goal of the model. Highly detailed physiological models (Wilhelms-Tricarico, 1995) are used to describe tongue physiology and function. Simpler, [...], This study demonstrated that a simple mechanical model of global tongue movement in parallel sagittal planes could be used to quantify tongue motion during speech. The goal was to represent simply the differences in 2D tongue surface shapes and positions during speech movements and in subphonemic speech events such as coarticulation and left-to-right asymmetries. The study used tagged Magnetic Resonance Images to capture motion of the tongue during speech. Measurements were made in three sagittal planes (left, midline, right) during movement from consonants (/k/, /s/) to vowels (/i/, /a/, /u/). MR image-sequences were collected during the C-to-V movement. The image-sequence had seven time-phases (frames), each 56 ms in duration. A global model was used to represent the surface motion. The motions were decomposed into translation, rotation, homogeneous stretch, and in-plane shear. The largest C-to-V shape deformation was from /k/ to /a/. It was composed primarily of vertical compression, horizontal expansion, and downward translation. Coarticulatory effects included a trade-off in which tongue shape accommodation was used to reduce the distance traveled between the C and V. Left-to-right motion asymmetries may have increased rate of motion by reducing the amount of mass to be moved. KEY WORDS: Cine-MRI, tongue deformation, tongue model, speech mechanics, speech production

To improve the naturalness of synthesized voices, the relations between the physical characteristics of the synthesized voices and the psychological effects should be established. The authors performed a psychological evaluation using natural voices of men and women as stimuli. The method of principal component analysis was applied to intercorrelations, the numerical ratings of the evaluation, and principal components were extracted which represented aspects ordinary people use to evaluate natural voices. Pitches of the voices used in the evaluation were analyzed as samples of physical voice parameters, and the relations between the pitches and the principal components were examined. Four principal components were extracted, representing aspects to which most people were observed to pay most attention when listening to voices. A significant relation was also found between physical pitches which were standardized by sex and the perceived pitches which were introduced from the principal component scores. This finding suggests that different criteria are used for perceptions of pitches of men and women.

Phonation threshold pressure (PTP) is the minimum subglottal pressure required to initiate vocal fold oscillation. Although potentially useful clinically, PTP is difficult to estimate noninvasively because of limitations to vocal motor control near the threshold of soft phonation. Previous investigators observed, for example, that trained subjects were unable to produce flat, consistent oral pressure peaks during/pae/syllable strings when they attempted to phonate as softly as possible (Verdolini-Marston, Titze, & Druker, 1990). The present study aimed to determine if nasal airflow or vowel context affected phonation threshold pressure as estimated from oral pressure (Smitheran & Hixon, 1981) in 5 untrained female speakers with normal velopharyngeal and voice function. Nasal airflow during /p/ occlusion was observed for 3 of 5 participants when they attempted to phonate near threshold pressure. When the nose was occluded, nasal airflow was reduced or eliminated during/p/; however, individuals then evidenced compensatory changes in glottal adduction and/or respiratory effort that may be expected to alter PTP estimates. Results demonstrate the importance of monitoring nasal flow (or the flow zero point in undivided masks) when obtaining PTP measurements noninvasively. Results also highlight the need to pursue improved methods for noninvasive estimation of PTP. KEY WORDS: phonation threshold pressure, glottal volume velocity, larynx, vocal folds, velopharyngeal insufficiency

This study observes in detail an [F.sub.0]/2 (sounding an octave below an original tone) subharmonic vibratory pattern produced in a normal larynx. Simultaneous electroglottographic and photoglottographic measurements reveal two different open phases within a subharmonic cycle - the first shorter with a simple shape, the second longer with a shape containing a 'ripple.' Such parameters as the large open quotient (ca. 0.8) and the high airflow values (ca. 1000 [cm.sup.3]/s) distinguish this phonation from the vocal fry (pulse) register. Using an electronic divider to track the subharmonic frequency, a method has been developed to observe the subharmonic vibration of the vocal folds stroboscopically. The stroboscopic visualization reveals an unusual mucosal movement during the 'ripple,' characterized by an opening movement of the upper margins, which interrupts the closing movement of the vocal folds. An explanation is offered that this vibratory pattern arises as a consequence of detuning of the usually identical frequencies of the dominant modes of the vocal folds, with 3:2 entrainment replacing the normal 1:1 pattern. KEY WORDS: vocal folds, stroboscopy, vibrational modes, bifurcation, entrainment

We hypothesized that acoustic measures would predict dysphonic severity with differential results for pathological voice types. An instructional program based upon synthesized voice signals was developed to facilitate an awareness of prototypical voice types. Eighty phonatory samples representing normal subjects as well as patients with unilateral vocal fold paralysis, vocal nodules, and functional dysphonia were analyzed acoustically on the basis of four measures: average fundamental frequency ([F.sub.0]), jitter, shimmer, and harmonic/noise ratio (H/N ratio). Following training, 29 listeners classified 62% of the phonatory samples on the basis of breathy, hoarse, rough, and normal. Dysphonic severity of rough voices was predicted more successfully by H/N ratio ([r.sub.2] = .73) than by shimmer ([r.sub.2] = .43). Dysphonic severity of breathy voices was predicted only by the combined features of less jitter, more shimmer, and lower H/N ratio ([r.sub.2] = .74). No combination of acoustic variables was successful in the prediction of the hoarse voice type. KEY WORDS: pathologic, voice, quality, acoustic, prediction

The perioral region was divided into four quadrants, and electromyograms (EMGs) were recorded from each area. The coherence function (i.e., the squared cross correlation between two signals computed at each frequency in the spectrum) was used to determine aspects of the organization of motor unit territories and to examine potential higher level sources of input in speech and nonspeech tasks. Coherence functions were computed between pairs of EMGs and were examined for significant values in the range of 20-240 Hz. When two pairs of electrodes were intentionally placed to record the activity from a common subset of motor units in a single quadrant of the lower lip, all subjects exhibited significant broad-band coherence in every frequency in all experimental tasks. Thus, the presence of such a pattern of broad-band significant coherence for EMG pairs recorded from different quadrants would indicate that single motor unit territories extended across perioral quadrants. When separate EMG recordings were obtained from the four quadrants of the lips, coherence functions computed between EMG pairs were typically zero across the entire frequency range. These findings suggest that perioral motor unit territories are organized into nonoverlapping quadrants. Further, the present analyses suggest that, unlike bilateral pairs of jaw-closing muscles during chewing, these motor units are not driven by any correlated oscillatory activity in chewing or other oral motor tasks. KEY WORDS: perioral, electromyography, coherence function, motor units, speech

This study examined laryngeal airway resistance (RLAW) in 10 healthy male and 10 female subjects within three age groups (55:0-64:11; 65:0-74:11; and 75:0+ years). A noninvasive procedure (Smitheran & Hixon, 1981) was employed to investigate RLAW at four vocal sound pressure levels (SPL) (25th, 50th, 75th percentiles of the SPL range, and comfortable voice level [CV]). RLAW values for the oldest group of females were found to be higher at each SPL percentile than those of the two younger age groups. The oldest group of males differed from the youngest group of males in RLAW values only at the 75th percentile level of SPL. Laryngeal airway resistance values were higher for females than males. As a group, the females generally had transglottal airflow that increased or remained relatively steady, whereas males maintained more linear changes in transglottal airflow and transglottal pressure as relative SPL increased. The present results suggest that separate norms need to be employed for males and females when determining RLAW values. Further, consideration should be given to examining the underlying airflow and pressure values when evaluating or monitoring changes in aerodynamic activity during voice production.

The purpose of this investigation was to study the impact of hearing loss on phonatory, velopharyngeal, and articulatory functioning using a comprehensive physiological approach. Electroglottograph (EGG), nasal/oral air flow, and intraoral air pressure signals were recorded simultaneously from adults with impaired and normal hearing as they produced syllables and words of varying physiological difficulty. The individuals with moderate-to-profound hearing loss had good to excellent oral communication skills. Intraoral pressure, nasal air flow, durations of lip, velum, and vocal fold articulations, estimated subglottal pressure, mean phonatory air flow, fundamental frequency, and EGG abduction quotient were compared between the two subject groups. Data from the subjects with hearing loss also were compared across aided and unaided conditions to investigate the influence of auditory feedback on speech motor control. The speakers with hearing loss had significantly higher intraoral pressures, subglottal pressures, laryngeal resistances, and fundamental frequencies than those with normal hearing. There was notable between-subject variability. All of the individuals with profound hearing loss had at least one speech/voice physiology measure that fell outside of the normal range, and most of the subjects demonstrated unique clusters of abnormal behaviors. Abnormal behaviors were more evident in the phonatory than articulatory or velopharyngeal systems and were generally consistent with vocal fold hyperconstriction. There was evidence from individual data that vocal fold posturing influenced articulatory timing. The results did not support the idea that the speech production skills of adults with moderate-to-profound hearing loss who are good oral communicators deteriorate when there are increased motoric demands on the velopharyngeal and phonatory mechanism. Although no significant differences were found between the aided and unaided conditions, 7 of 10 subjects showed the same direction of change for subglottal pressure, intraoral pressure, nasal air flow, and the duration of lip and vocal fold articulations. We conclude that physiological assessments provide important information about the speech/voice production abilities of individuals with moderate-to-profound hearing loss and are a valuable addition to standard assessment batteries.

Voice perturbation measures, such as jitter and shimmer, depend on accurate extraction of fundamental frequency (F(sub o)) and amplitude of various waveform types. The extraction method directly affects the accuracy of the measures, particularly if several waveform types (with or without formant structure) are under consideration and if noise and modulation are present in the signal. For frequency perturbation, high precision is defined here as the ability to extract F(sub o) to + or - 0.01% under conditions of noise and modulation. Three F(sub o)-extraction methods and their software implementations are discussed and compared. The methods are cycle-to-cycle waveform matching, zero-crossing and peak-picking. Interpolation between samples is added to make the extractions more accurate and reliable. The sensitivity of the methods to different parameters such as sampling frequency, mean F(sub o), signal-to-noise ratio, frequency modulation, and amplitude modulation are explored.

The purpose of this investigation was to examine intrasubject and intersubject fundamental frequency ([F.sub.o]) variability in a group of young adult and elderly female speakers during the production of stressed and unstressed words. While both groups exhibited greater intersubject variability during stressed versus unstressed productions, stressed productions were more variable in the elderly women than in the young adults. Also, the elderly women exhibited greater intrasubject variability during stressed and unstressed productions relative to young adults. Implications of these findings were discussed.

In a previous radiographic study of 4 deaf women, some aberrant features in vocal tract configuration were identified for vowels produced with excessive pharyngeal resonance. These features included neutralization of tongue position, elevation of the hyoid, and a retraction of the tongue, associated with a deflection of the epiglottis in the lower pharynx. The vowels, produced simultaneously with X-ray exposure, were analyzed spectrographically to study acoustic correlates of the vocal tract deformation. Comparisons of the formants for vowels /i/ /u/ and /a/ produced by the deaf women with mean formant values for these vowels produced by normal-hearing women revealed no consistent pattern of second-formant deviation. Formant structure evaluated on isovowel lines disclosed consistent neutralization of vowels, with [F.sub.2] values clustering in the 1500-2100 Hz frequency range, which is attributed to the observed restricted horizontal movements of the tongue within the oral and pharyngeal cavities. If such restrictions affect the production of all vowels, a lower [F.sub.2] might be assumed for the front vowels, which normally have a high [F.sub.2]; a higher [F.sub.2] frequency would be anticipated for back vowels, which normally have a low [F.sub.2] The limited sample studied supports this assumption.

Electroglottographic (EGG) and acoustic records from 10 normal men prolonging the vowel /a/ at 60-68 dB, 70-78 dB, and 80-88 dB SPL were obtained. 'Contact quotient' (EGG duty cycle) was shown to vary directly with vocal SPL. The mean contact quotient was 0.57 (SD = 0.07) and varied on the order of 1% over the course of a given phonation. 'Contact index,' a metric of EGG symmetry, also tended to vary with SPL. Consistent with previous qualitative descriptions of EGG morphology in modal register voice, the contact index averaged -0.52 (SD = 0.08), indicating that the EGG 'closing phase' represents about 24% of the entire 'contact phase.' Contact index was more variable than contact quotient on consecutive EGG waves, varying by about 10% during phonation. Subjects were also instructed to produce a slow crescendo. Sound pressure and EGG data indicated that both the slope of increasing EGG contact and EGG duty cycle were significantly related to the amplitude of the acoustic signal. These results suggest that quantitative electroglottography may provide powerful insights into the control and regulation of normal phonation and into the detection and characterization of pathology. KEY WORDS: electroglottography, vocal fold contact, vocal fold vibration, contact quotient, contact index

The mammalian hypoglossal canal transmits the nerve that supplies the muscles of the tongue. This canal is absolutely and relatively larger in modern humans than it is in the African apes (Pan and Gorilla). We hypothesize that the human tongue is supplied more richly with motor nerves than are those of living apes and propose that canal size in fossil hominids may provide an indication about the motor coordination of the tongue and reflect the evolution of speech and language. Canals of gracile Australopithecus, and possibly Homo habilis, fall within the range of extant Pan and are significantly smaller than those of modern Homo. The canals of Neanderthals and an early 'modern' Homo sapiens (Skhul 5), as well as of African and European middle Pleistocene Homo (Kabwe and Swanscombe), fall within the range of extant Homo and are significantly larger than those of Pan troglodytes. These anatomical findings suggest that the vocal capabilities of Neanderthals were the same as those of humans today. Furthermore, the vocal abilities of Australopithecus were not advanced significantly over those of chimpanzees whereas those of Homo may have been essentially modern by at least 400,000 years ago. Thus, human vocal abilities may have appeared much earlier in time than the first archaeological evidence for symbolic behavior.