Transglottal Pressure Research Articles

Pressure profiles on the walls of the glottis for oblique glottal ducts

Oblique angles of the glottis occur during both normal and abnormal phonation. This study examined pressures on the glottal walls for a variety of oblique angle conditions. A Plexiglas model of the larynx was used to obtain wall pressures at 14 taps along the glottal surfaces. The model is 7.5 times larger than real life. A minimal diameter of 0.04 cm and duct axial length of 0.3 cm were used for all cases. Results indicated, for example, that for an included angle of 10 deg (divergence) and a transglottal pressure of 5-cm H2O, an oblique glottal angle of 15 deg compared to the symmetric glottis: (1) displaced the minimal wall pressure location on the divergent side a short distance downstream and on the convergent side to mid-glottis; (2) increased the pressure drop on the divergent side by about 15% and decreased the pressure drop on the convergent side by about 13%; and (3) broadened the minimum pressure dip on both the divergent and convergent sides. These results suggest paradoxical (opposite) driving pressures on the inferior glottal walls, which would enhance the nontypical phase differences between the two vocal folds. [Research support: NIH grant 1R01DC03577.]

Vowel-dependent VOT variation: An experimental study

That the VOT of voiceless stops is typically longer before high, close vowels and shorter before low, open ones is well documented. The hypothesis was tested that high vowels engender longer VOT because they offer greater resistance to the air escaping from the mouth (thereby delaying the transglottal pressure differential required for voicing). A correlation was sought between oral pressure decay (OPD) and VOT. Acoustic and aerodynamic data were collected from a male native speaker of American English uttering 12 nonsense words of the type atí, atà in isolation ten times. Pressure data was sampled by inserting a tube into the subject’s pharyngeal cavity via the nose. The VOT was measured from the release of the burst to the onset of the first periodic cycle. The OPD was defined as the time required for oral pressure to decrease from the peak to a fixed low threshold. The OPD and VOT measurements displayed a significant, linear correlation, indicating that VOT and vowel height are indeed mechanically linked. Moreover, tokens with voiceless stops preceding sonorants, e.g., atwà, akjà, yielded the longest VOTs since sonorants have narrower constrictions, resulting in longer OPDs.

Combined simulation of two-dimensional airflow and vocal-fold vibration

Self-sustained oscillation of the vocal folds was simulated by combining two-dimensional laryngeal airflow with multidimensional tissue movement. A finite-element model was used for the solution of viscoelastic waves in the tissue and a finite-volume method was used in the solution of Navier–Stokes equations for the airflow. A so-called ‘‘shadow method’’ simulated the glottal constriction in the flow model to avoid the complexity of grid movement. The two-dimensional flow equations were solved in an iterative manner until the given transglottal pressure was approximated. The flow solution was then used in the estimation of the aerodynamic forces on the tissue, required in the finite-element solution of tissue movement. The results indicate that inlet velocity profiles to the glottis are almost parabolic at any instant of time. The glottal velocity increases to its maximum at the glottal exit at the center of a jet, with values exceeding 40 m/s for 0.8 kPa of lung pressure. The jet velocity waveform is similar to that of an excised larynx and the pressure profiles are similar to those of steady flows in physical models. Also, the displacement of the inferior portion of the vocal folds leads the superior position in phase.

Influence of transglottal pressure on vocal fundamental frequency changes with stiffness of vocal folds

We have described the influence (dF/dP) of transglottal pressure on vocal fundamental frequency (F0). It was previously reported that dF/dP varied with the stiffness of the vocal folds, and that the vocal fold membrane when dry was stiffer than when wet. Normal subjects were injected with atropine sulfate in order to dry their larynx, as a model of stiffer-than-normal vocal folds. Transglottal pressure changes during sustained phonation were applied by partially closing a shutter valve mounted on a mouthpiece. Both before and after atropine sulfate injection, the values of dF/dP, in modal register, decreased and increased as F0 increased, and the smallest values of dF/dP were negative in all subjects. The absolute values of both the largest and smallest dF/dP in subjects with atropine sulfate were smaller than those in normal subjects. These finding indicated that dF/dP is correlated with the stiffness of the vocal folds.

Recent advances in monitoring techniques for speech production

In recent years, various techniques have been developed for monitoring the dynamics of articulatory and phonatory systems. For the articulatory system, x-ray, ultrasound, magnetic field, etc., have been utilized. Among them, MRI is most preferable because of high spatial resolution and safety, though it has to be supplemented by other techniques due to its limited temporal resolution. Recent results on tagged MRI of the tongue will be discussed. For the phonatory system, high-speed monitoring of vocal fold vibration is quite important in the study of voice production in normal as well as in pathological cases. A high-speed imaging technique up to 9000 frames per second has been developed, and is being used in this laboratory for recording fiberscopic images of the vocal fold vibration during running speech, singing, and other vocal activities. Aerodynamic measurement is also important for studying various modes of phonation. The difficulty of measuring the transglottal pressure is being overcome by the use of a miniaturized pressure transducer which can be inserted into the subglottic space. These new techniques provide a lot of new data as well as allow new interpretation of already existing data.

Phonetic mechanisms of post-nasal voicing

Many languages systematically replace voiceless stops by voiced stops when the immediately preceding sound is nasal. This is estimated to occur in 7% of all languages, and thus is likely to reflect preferences of the speech production mechanism. Post-nasal voicing can be explained by two factors. Coarticulation with an adjacent nasal induces nasal leak during a stop, which vents oral pressure and tends to maintain the transglottal pressure drop needed to sustain voicing. Coarticulation also causes the velum to rise or fall during the stop while the velar port is closed. This creates a pumping effect (rarefaction in post-nasal stops, compression in pre-nasal), which facilitates voicing for post-nasal stops and inhibits voicing for pre-nasal stops. The cross-linguistic pattern of post-nasal voicing reflects the combined effects of nasal leak and rarefactive velar pumping; the absence of pre-nasal voicing reflects the antagonistic effects of nasal leak and compressive velar pumping. To test this hypothesis, an aerodynamic vocal tract model [J. Westbury and P. Keating, J. Linguist.22 , 145–166 (1986)] was used. Over a range of estimated values for nasal leak and velar pumping, the model output a strong preference for extra voicing post-nasally, and no preference for pre-nasal voicing.

空力的側面より観察した声の高さの調節機構

The effects of transglottal pressure on fundamental frequency of phonation (dF/dP) were investigated by loading a sudden transglottal pressure change during sustained phonation.1) Human experimentsFourteen human subjects participated. The results showed that the values of dF/dP within the modal register were smallest around 200 Hz in males, and 250-400Hz in females and children. The values of dF/dP as a function of F0 varied following a V-shaped pattern, indicating that the role of transglottal pressure on F0 was not only important in low modal register, but also in high modal register.2) Dog experimentsFive dogs were involved. The forced phonation under simulated activities of cricoarytenoid (CT) muscles and thyroarytenoid (TA) muscles showed that the CT muscle activities have the strongest effects on the V-shaped pattern.Human and dog experiments revealed the definite role of transglottal pressure for regulation of F0 in high modal register.

The effect of gas density on glottal vibration and exit jet particle velocity.

Although theoretical studies include a term for gas density in their mathematical descriptions of glottal aerodynamics, the effect of gas density on glottal vibration has not been examined empirically. In this study, an in vivo canine model was used to evaluate the effect of gas density on glottal vibration by comparing phonation with air and helium. With gas flow and nerve stimulation held constant, phonation with helium resulted in an increased exit jet particle velocity for helium (45 m/s) compared to air (34 m/s). However, the measured increase in helium velocity was less than predicted by a proportional relationship between transglottal pressure and dynamic pressure. This difference could be due to a change in the constant of proportionality or in the dynamic pressure loss coefficient associated with the use of helium.

声門上下圧差突然変化と音声基本周波数 声帯のｓｔｉｆｆｎｅｓｓ評価の可能性

The change of fundamental frequency (F0) per unit change of transglottal pressure (dF/dP) is determined by the amount of displacement of the vocal folds. Since the amount of displacement varies with the stiffness of the vocal folds, this study was designed to determine whether the stiffness of the vocal folds can be evaluated with dF/dP. In a preliminary study the correlation between F0 and dF/dP was examined in normal subjects; 14 humans and 5 dogs.Method. 1) Transglottal pressure (Pt) changes were produced during sustained phonation in 6 male, and 6 female adults and 2 children. The pressure changes were applied by closing a shutter valve mounted on a mouthpiece. F0 and intraoral pressure were measured. 2) Pt changes were produced in 5 living adult dogs. The pressure changes were applied by closing a shutter valve mounted on a tube for insufflating the larynx. F0 and subglottal pressure were measured.Result. 1) The values of dF/dP, in modal register, decreased linearly and increased linearly as F0 increased in all subjects. The smallest values of dF/dP were observed around 200-250Hz in males and 250-300Hz in females and children. The value of dF/dP was larger in falsetto voice in terms of the same F0 between high pitch modal register and low pitch falsetto. 2) The same pattern of correlation between F0 and dF/dP was also observed in adult dogs. The correlation between F0 and dF/dP in this study indicated a potential usefulness for the evaluation of the stiffness of the vocal folds.

Incorporating aerodynamic and laryngealcomponents into task dynamics

Aerodynamic and laryngeal components were added to the task-dynamic model to make it a more complete model of speech production. New tract variables included were subglottal pressure, transglottal pressure, and a quantity giving fundamental frequency in sonorant conditions. New articulators included total force on the lungs, generalized laryngeal tension, and supralaryngeal volume. Simulations of /VCV/ sequences, where C was either a voiced or a voiceless aspirated stop, demonstrated the usefulness of these additions.

空力的側面よりみた音声基本周波数の調節

The change of Fo per unit change of transglottal pressure (dF/dP) was investigated. Since the length and stiffness of the vocal folds determine the values of dFldP, it was expected that the relationship between dF/dP and Fo would show the effects of these adjustments of the vocal folds. Six males and six females participated in this study.A specially designed tube is equipped with a mouthpiece into which the subject phonates and a shutter valve which can be partially closed during sustained phonation to create a sudden pressure increase inside the tube. The voice signal was picked up by a throat contact microphone and fed into the microcomputer simultaneously with the pressure reading inside the tube (Po). The valve was programmed to close for 300 msec during the utterance. The subjects repeated the utterance at different pitches which were raised by small steps. The computer program was designed to calculate the change of Fo per unit change of Po (dF/dP).Within the modal register, the values of dF/dP became smaller with Fo up to 200 Hz in males, and up to 250-400 Hz in females. With Fo higher than these levels, dF/dP became larger. The values of dF/dP in the modal register were smaller than those in the falsetto register. On the basis of these observations, we suggest that there is a difference between low-pitched modal register and high pitched modal register in the manner of adjustments of length and stiffness of the vocal folds.

A Navier–Stokes solution of laryngeal flow during vocal fold oscillations

Dynamic modeling of vocal fold tissue movement and laryngeal airflow was combined in a computer simulations for the purpose of voice production. A finite-element model was used for the solution of tissue mechanics and a finite volume method was used in the solution of Navier–Stokes equations for the airflow. A so-called ‘‘shadow method’’ simulated the glottal constriction in the flow model to avoid the complexity of grid movement. The two-dimensional flow equations were solved in an iterative manner until the given transglottal pressure was approximated. The flow solution was then used in the estimation of the aerodynamic forces on the tissue, required in the finite element solution of tissue movement. The results indicate that glottal velocity profiles are parabolic, with maximum velocity in the exiting jet reaching 35 m/s. The time-varying Reynolds number in the glottis can reach up to 1500 at a lung pressure of 8 cm water. The jet velocity waveform is similar to that of an excised larynx and the pressure profiles are similar to those of steady flows in physical models. Also, the displacement of the inferior portion of glottis shows previously described phase differences with the superior portions. [Work supported by NIDCD Grant No. DC00831-03.]

Characterization of noise during glottal vibration: Measurements performed on a mechanical model

Speech synthesis and coding schemes commonly incorporate a random noise component during voicing. It is hard to isolate this noise in recorded speech because of the inaccuracy of characterizing a modulated random process from a few nonidentical periods with a strong periodic component. Direct measurement on humans poses many clinical difficulties. Computational hydrodynamic modeling is difficult, and reliable modeling of turbulence is an unsolved problem. Here, direct steady-state measurements are made on a detailed, life-size mechanical model. A molded rubber model of the vocal cords is driven synchronously with the sampling clock so that precise repetitions of pitch periods are generated. The random component of the recording is isolated by subtracting away the periodic component (obtained by ensemble averaging across 1000 pitch periods). The noise power and its spectrum at each point in the pitch period are estimated by ensemble averaging the autocorrelations of the noise. The noise results are well explained in terms of the directly measured transglottal pressure and glottal area. In high-passed human speech, bursts of noise appear to overlap the closed-glottis interval. To explain this, it is necessary to include transit time for glottal air bursts to reach an obstruction 2–3 cm downstream. a)Also a student at MIT.

Aerodynamic assessment of the speech of adults undergoing multichannel cochlear implantation.

This investigation was designed to evaluate the aerodynamic characteristics of the speech of adult multichannel cochlear implant (Nucleus, 21-channel) recipients. Five adults with an acquired profound sensorineural hearing loss were tested before implantation, immediately following implantation, and 3, 6, 9, and 12 months after implantation. A commercially available computerized pressure-flow instrumentation system was employed to assess the respiratory, laryngeal, velopharyngeal, and oral articulatory subsystems of speech of the implantees. The results of the investigation indicated 1) a slight increase in airflow rate values for sustained vowel /a/phonation after implantation, 2) a slight increase in duration of sustained vowel phonation from the preimplant period to the last postimplant period, 3) an increase in laryngeal airway resistance after implantation that resulted from a larger increase in estimated transglottal pressure than in transglottal airflow, 4) maintenance of normal velopharyngeal closure in oral-nasal contrastive contexts, and 5) slight increases in oral orifice area for fricative syllable utterances following implantation. Individual strategies for coordinated control of the speech mechanism appear to be potent variables to consider when assessing speech production.

Intraoral pressure in the evaluation of laryngeal function.

The difference in peak intraoral pressure between the consonants /p/ and /b/ (abbreviated as Pr./p-b/) showed a significant correlation with the transglottal pressure during consonant /b/ production. The values of Pr./p-b/ in subjects with vocal fold palsy were smaller than those in subjects with a cancer or polyp. The values of Pr./p-b/ divided by the estimated subglottal pressure in the subjects with cancers showed different distributions from those in subjects with palsies, polyps and in normal subjects. These parameters have potential benefit for the evaluation of pathological conditions of the glottis, especially for insufficient closure of the glottis and high stiffness of the vocal folds.

Acoustic and aerodynamic effects of interarticulator timing in voiceless consonants.

Interarticulator timing is a mechanism for producing linguistic contrasts that is widely used in different languages. This paper explores acoustic and aerodynamic effects of variations in laryngeal-oral coordination in voiceless consonants. Measurements of voice onset time and interarticulator phasing for individual tokens of stop consonants show weak correlations, indicating that interarticulator timing is only one factor determining voice onset time. Other factors most likely involved are glottal opening, transglottal pressure and air flow, and vocal fold tension. Taken together, these observations suggest that speakers may only have limited control of voice onset time. This could explain why languages do not seem to make fine-grain use of VOT for linguistic contrasts. Measurements of peak and minimum air flow during individual source pulses, obtained by inverse-filtering oral flow, show a pattern of decrease and increase in vowels following voiceless consonants. Subtle differences in the time course of these patterns occur following different consonants, suggesting that interarticulator phasing may be partly responsible for them. Closer examination reveals consistent correlations with interarticulator phasing for one speaker but inconsistent results for another. The results are discussed in terms of speech motor control and controlled variables in speech.

Clinical report on preliminary data on intraoral pressure in the evaluation of laryngeal pathology

<h2>Summary</h2> The consonant /b/, when surrounded by vowels, is accompanied by vocal fold vibration even during occlusion of the supraglottal cavity. Since the voicing of /b/ involves a relatively loose closure of the glottis and smaller amplitudes of vibration than those observed during the production of vowels, the transglottal pressure during /b/ production approximates that of the oscillation threshold pressure. Since the intraoral pressure of /p/ production is approximately equal to subglottal pressure of the surrounding vowels, the differences in peak intraoral pressure between the productions of /i:pi:/ and /i:bi:/ can be assumed to reflect the transglottal pressure during /b/ production. In a clinical investigation, the differences in the peak intraoral pressures of /i:pi:/ and /i:bi:/ were found to be higher in conditions typified by stiff vocal folds, such as laryngeal cancer and partial laryngectomy, than in those typified by flaccid folds, such as vocal cord polyp and palsy. This suggests that the intraoral pressure differences between /i:pi:/ and /i:bi:/ may constitute a parameter indicative of vocal cord stiffness

Control of fundamental frequency, intensity and voice quality in speech

In this paper the control of fundamental frequency, intensity level of the radiated acoustic signal and voice quality is studied in normal conversational speech. It is shown that the physiological factors that best explain measured features of the speech wave depend on the part of the utterance taken into account. Also, it appears that in speech, transglottal pressure is more important than subglottal pressure. We conclude that currently available mathematical models that describe the waveform of glottal volume flow lack a number of parameters necessary for a better understanding of the physiological control of the speech parameters investigated in this study.

Intraspeaker variation in aerodynamic and acoustic parameters of voice production across repeated recordings

In a previous study of aerodynamic and acoustic measurements of voice production for groups of female and male speakers to establish normative data, interspeaker variation was often found to be highly correlated with SPL [Holmberg et al., J. Acoust. Soc. Am. 84, 511–529 (1988)]. In this study intraspeaker variation across three recordings is examined for each of three female and three male speakers. Measurements were made from the inverse filtered air‐flow waveform, of estimated average transglottal air pressure and glottal air flow, and the amplitude difference between the two first harmonics of the acoustic spectrum for productions of syllable sequences in soft, normal, and loud voice. Although the results show different patterns across both speakers and intensity conditions, preliminary observations reveal that a small amount of SPL variation could be accompanied by large variation in other parameters. For some parameters, the variation was strongly related to SPL, for others not. Statistical analyses will be performed to compare the intraspeaker variation across recordings with interspeaker variation from normal group data, in order to help quantify normal variation. [Work supported by NIH.]

Phonatory function associated with hyperfunctionally related vocal fold lesions

A combination of noninvasive acoustic and aerodynamic measures were used to compare and contrast vocal function among patients having one of four major types of hyperfunctionally related vocal fold lesions: nodules, polyps, polypoid degeneration, or contact ulcers. Measures included: (a) vocal intensity and fundamental frequency, (b) parameters derived from inverse filtered approximations of the glottal airflow waveform and (c) estimates of transglottal pressure and average glottal airflow. Preliminary results showed that a combination of measures of fundamental frequency, transglottal pressure, and maximum declination rate of the glottal airflow waveform appeared to differentiate among three of the different types of lesions studied (nodules, polypoid degeneration, and contact ulcers). These results were interpreted as evidence that different underlying phonatory mechanisms are associated with different types of hyperfunctionally related vocal fold lesions. A combination of noninvasive acoustic and aerodynamic measures were used to compare and contrast vocal function among patients having one of four major types of hyperfunctionally related vocal fold lesions: nodules, polyps, polypoid degeneration, or contact ulcers. Measures included: (a) vocal intensity and fundamental frequency, (b) parameters derived from inverse filtered approximations of the glottal airflow waveform and (c) estimates of transglottal pressure and average glottal airflow. Preliminary results showed that a combination of measures of fundamental frequency, transglottal pressure, and maximum declination rate of the glottal airflow waveform appeared to differentiate among three of the different types of lesions studied (nodules, polypoid degeneration, and contact ulcers). These results were interpreted as evidence that different underlying phonatory mechanisms are associated with different types of hyperfunctionally related vocal fold lesions.