The effects of changes in speaking rate on nasal airflow and the perception of nasality.

The effects of variation in speaking rate on relative nasal airflow (percent nasal flow) and on the perception of nasality were examined. In addition, the effects of gender and speech rate elicitation techniques (metronome-controlled, self-controlled) were examined. Nineteen normal speakers each produced a stimulus phrase containing nonnasal sounds. Oral and nasal airflows were measured using the Rothenberg aerodynamic system. Results indicated that percent nasal flow and perception of nasality were both greater at slow speaking rates compared to normal and fast rates. Males were perceived as more nasal than females. The metronome-controlled rates were associated with greater nasality than the self-controlled rates. Discussion focuses on physiological correlates to these findings.

A study of sentence stress production in Mandarin speakers of American English.

Acoustic characteristics of American English sentence stress produced by native Mandarin speakers are reported. Fundamental frequency (F0), vowel duration, and vowel intensity in the sentence-level stress produced by 40 Mandarin speakers were compared to those of 40 American English speakers. Results obtained from two methods of stress calculation indicated that Mandarin speakers of American English are able to differentiate stressed and unstressed words according to features of F0, duration, and intensity. Although the group of Mandarin speakers were able to signal stress in their sentence productions, the acoustic characteristics of stress were not identical to the American speakers. Mandarin speakers were found to produce stressed words with a significantly higher F0 and shorter duration compared to the American speakers. The groups also differed in production of unstressed words with Mandarin speakers using a higher F0 and greater intensity compared to American speakers. Although the acoustic differences observed may reflect an interference of L1 Mandarin in the production of L2 American English, the outcome of this study suggests no critical divergence between these speakers in the way they implement American English sentence stress.

Acoustic comparison of vowel articulation in normal and reverse phonation.

Acoustic characteristics of the vowels /i,u,a/ produced by adult females and males during normal phonation were compared with the same vowels produced on deliberate ingressive airflow (i.e., "reverse" phonation). Results of the analysis revealed the average fundamental frequency (F0) of reverse phonation to be significantly higher than the corresponding normal phonations. There were no significant differences noted in the vocal tract resonance (F1 and F2 frequency) values for /i/ during normal and reverse phonation. However, the F1 values for /a/ were significantly lower, and the F2 values for /u/ significantly higher, during reverse phonation. The results are discussed with regard to differences in the articulatory control of the speech mechanism during reverse phonation as compared to normal expiratory phonation. Also discussed are the implications of using reverse phonation as a voice management technique.

Fundamental frequency, intensity, and vowel duration characteristics related to perception of Cantonese alaryngeal speech.

Fundamental frequency (F(0)), F(0) contours, vowel duration, and intensity associated with Cantonese alaryngeal speech, and their relation to the perception of meaning were studied. Thirty adult male native Cantonese speakers participated in the study: 10 esophageal, 10 electrolaryngeal, and 10 laryngeal speakers. Results indicated that perceptually, listeners were able to identify what the Cantonese esophageal speakers were saying, particularly for words associated with high-level, low-falling and high-rising tonal contours. Acoustic analysis of the speech signals of the esophageal speakers indicated that intensity and durational data did not contribute to the perception of meaning. The F(0) contours appeared to be the acoustic cues associated with the signal that contributed most to the perception of meaning.

An acoustic analysis of excellent female esophageal, tracheoesophageal, and laryngeal speakers.

Acoustic data for female esophageal speakers is sparse, particularly with regard to characteristics of female tracheoesophageal speakers. This study quantified and compared six acoustic characteristics of excellent female tracheoesophageal (TE), standard esophageal (SE), and laryngeal (LA) speakers. Results indicated there were no significant differences between TE and SE speakers with regard to mean F0 of sustained /a/, mean F0 (reading), signal-to-noise ratio, total duration of passage read, number of pauses, or syllables per minute. Significant differences were found between LA speakers and both alaryngeal groups for all variables, with the exception of mean F0 (reading).

Perceptions of tonal changes in normal laryngeal, esophageal, and artificial laryngeal male Cantonese speakers.

Listeners were asked to identify six tonal variations in the production of the syllables /ji/ and /si/ produced by 10 normal laryngeal (NL), 10 standard esophageal (SE), and 10 Servox-type electrolarynx (EL) Cantonese speakers. The purpose of the present study was to determine if alaryngeal Cantonese speakers could differentiate meanings associated with different tone levels. Results indicated that listeners' identification of the six tones for each syllable produced by the SE speakers was similar in pattern to those produced by the NL speakers of Cantonese. For both NL and SE speech, the high-level, low-falling, and high-rising tones were perceived more accurately than the mid-level, low-level, and low-rising tones. Identification of the six tones for each syllable as produced by the EL speakers was significantly poorer due to the limitations of the electrolarynx.

Acoustic, aerodynamic, physiologic, and perceptual properties of modal and vocal fry registers.

The purpose of the study was to examine the acoustic, aerodynamic, physiologic, and perceptual characteristics of modal and vocal fry production. Twenty normal speakers (10 males, 10 females) participated in the study. Speech material included four sustained vowels (/i/, /a/, /ae/, /u/), and syllable strings of /pi/ repetitions produced in both modal and vocal fry registers. Acoustic data (fundamental frequency, jitter, shimmer, and signal-to-noise ratio), aerodynamic data (airflow and air pressure), and electroglottographic (EGG) data were obtained simultaneously. Results demonstrated considerable differences across voice parameters for the modal and vocal fry registers. Fundamental frequency was significantly lower in vocal fry than in modal register for both males and females, however, significant gender differences existed only in modal register. For both males and females, measurements of jitter and shimmer were significantly higher and signal to noise ratio was significantly lower in vocal fry. In addition, airflow rate in modal register was almost three times as high as the airflow rate in vocal fry register during sustained vowel production. During syllable string production, subglottal air pressure values in modal register were approximately 1.5 times higher than that in the vocal fry register. In general, these data emphasize that the aeromechanical mechanisms of vocal fold vibratory behavior are substantially different between modal and vocal fry registers. A model of vocal fry phonation is presented to account for the present results.

Formant frequency development: 15 to 36 months.

Developmental characteristics of formant 1 (F1) and formant 2 (F2) are reported for spontaneous vocalizations produced by four young children. Each child was systematically sampled at between 15 and 36 months of age. Results indicated that both F1 and F2 remained relatively unchanged prior to 24 months of age. Significant decreases in average F1 and F2 occurred between 24 and 36 months. When F1 and F2 values were categorized according to tongue elevation and tongue advancement, the most significant changes were associated with high/back articulations. The pattern of formant frequencies noted in the present group of children appears to reflect developmental changes in vocal tract growth and reconfiguration.

Some aerodynamic and acoustic characteristics of acute laryngitis.

The purpose of the present study was to describe the effects of acute laryngitis on some aerodynamic, acoustic, and perceptual measures. Eleven subjects with diagnosed acute laryngitis due to upper respiratory infection were recorded during a laryngitic episode and 1 week to 10 days after amelioration of the laryngitic condition. Fundamental frequency, values, collapsed across the five vowels, were significantly reduced in the laryngitic compared with the normal speaking condition. The decrease in fundamental frequency associated with acute laryngitis suggests an increase in the mass of the vocal folds. In addition, aerodynamic values differed significantly for the laryngitic condition compared with the normal speaking condition, suggesting the presence of laryngeal hypofunction. Perceptual data indicated that speakers in the laryngitic condition were judged to have a hoarse voice when compared with the normal speaking condition.

Developmental aspects of formant frequency and bandwidth in infants and toddlers.

Average formant frequency and formant bandwidth values are reported in a cross-sectional sample of 20 children between 4 and 25 months of age. With the exception of a slight rise in F1 at 18 months of age, average F1 and F2 values changed little during the time period, while the average bandwidths for F1 (B1) and F2 (B2) were found to significantly decrease as age increased. The pattern observed for both average formant frequencies and formant bandwidths were attributed to developmental reconfiguration of the vocal tract.

Vocal fundamental frequency characteristics of infant hunger cries: birth to 12 months.

The vocal fundamental frequency (Fo) characteristics of four infants' hunger cries are reported. The infants were audio recorded at monthly intervals during the first year of life. In general, each infant's Fo increased across the one-year period. The increase in Fo was attributed to the transition from early reflexive crying to intentional vocalization behavior, rather than anatomical and physiological growth influences. Discussion focuses on the regulation of infant crying behavior across the first year of life, as well as the diagnostic implications of these findings.

A continuous-flow model for phonatory reaction time.

The purpose of this study was to validate a proposed continuous-flow model of phonatory reaction time by investigating the temporal order of selected laryngeal and neurophysiological events involved in a phonatory reaction time task. Ten normal speakers participated in a phonatory reaction time task. Laryngeal positioning movements prior to vocal fold closure (laryngeal shift) and onset of vocal fold vibration (acoustic onset) were recorded with an electroglottograph. P300 brain potentials were collected simultaneously, and they served as an index of a central process underlying reaction time. The obtained temporal ordering of laryngeal shift, P300, and acoustic onset supported a continuous-flow model of phonatory reaction time. Use of this model might yield information that is more accurate in explaining physiological function and more precise in describing temporal patterning than the serial model.

Nasal airflows in parkinsonian speakers.

Velopharyngeal control in individuals with Parkinson's disease (PD) was studied by obtaining rates of nasal airflow during syllable repetitions. Nasal airflows were described with respect to disease progression, phonetic context, and speaking rate. Significant differences in nasal airflows were obtained for disease progression and phonetic context. The data suggested that velopharyngeal control deteriorates systematically with disease progression. Parkinson's patients at mild and moderate levels of disease progression differentiated the nasal consonant from the oral consonants with increased nasal airflow associated with the nasal consonant. Differences, while not significant, were also observed in nasal flow rate values when the PD patients increased speaking rate from 1 to 5 syllables per second.

A respirometric technique to evaluate velopharyngeal function in speakers with cleft palate, with and without prostheses.

There is a paucity of respirometric quotient (RQ) data on individuals with velopharyngeal inadequacy. Paesani (1964) reported data using a technique that involved separate productions of the same task to obtain the RQ. The RQ values obtained were greater than unity, which is theoretically impossible. In the present study, respirometric quotients, the ratio of oral air volume expended to total volume expended, were obtained using separate but simultaneous productions of oral and nasal airflow. RQ values were calculated for 10 speakers with cleft palate, with and without their prosthetic appliances, and 10 normal speakers. As a group, those with cleft palate and without their appliances exhibited RQ values that were significantly lower than values obtained from the normal speakers and from speakers with the appliances in place. These findings indicated that there were no statistically significant differences in RQ values when comparing sentence repetition and counting tasks. These values were lower than those obtained for the nonnasal syllable repetition tasks, with the /mv/ syllable repetition task generally being associated with the lowest RQ value of any of the speech tasks. The correlation between RQ values and perceptual judgments was -.60, indicating that there was modest agreement between the two measures. As RQ values decreased, perceptual judgments of nasality increased.

Relation between voice profile ratings and aerodynamic and acoustic parameters.

The present study sought to examine the relation between Wilson Voice Profile ratings and certain aerodynamic and acoustic variables. Subjects in this study were 20 adults with voice disorders and five adults with no voice disorders. A series of stepwise multiple correlations were used. The variance in perceptual ratings accounted for by aerodynamic and acoustic variables included in the present study ranged from 29% for tension ratings of connected speech to 81% for pitch ratings of connected speech for the female speakers. It is clear from the present findings that ratings on the Wilson Voice Profile are only partially accounted for by the variables included in the present study.

Laryngograph as a measure of vocal fold contact area.

The present investigation sought to provide additional information concerning the laryngograph as a means to study vocal fold contact area. Subglottal pressures were sensed simultaneously with the laryngographic signal while the speaker produced a variety of speech tasks. The onset and cessation of the subglottal pressure waveform was studied relative to the laryngographic and speech waveforms. Differences were noted for voiced-voiceless contrasts for bilabial stop consonant production and vocal effort changes during the three vowels studied. Also a high-resistance polymer strip was placed between the vocal folds and gradually removed while simultaneous laryngographic recordings were obtained during sustained productions of the vowel /a/. An increase in the amplitude of the laryngographic waveform upon withdrawal of the polymer strip strongly supported the concept that the laryngographic signal is generated directly by the change in conductance due to alterations in the area of vocal fold contact.

Relation of selected acoustical parameters and perceptual ratings to voice quality of Down syndrome children.

Judges using the Wilson Voice Profile rated the voice quality of 14 noninstitutionalized, 7- to 10-year-old Down syndrome children and a group of nonretarded children. The Down syndrome children received ratings different from the nonretarded children on the Severity subscale of the Wilson Voice Profile. Voice samples were analyzed acoustically in terms of fundamental frequency, fundamental frequency range, frequency and amplitude perturbations, and spectral noise-to-harmonic component ratios. Frequency perturbations, amplitude perturbations, and spectral noise-to-harmonic component ratios were significantly greater for the Down syndrome children. There were also significant correlations between judges' Severity ratings and frequency perturbation levels, amplitude perturbations levels, and spectral noise-to-harmonic component ratios.

Preparation, purification and properties of a crosslinked trimer of G-actin.

Phenylenebismaleimide has been used to form crosslinks between actin monomers [Knight, P. and Offer, G. (1978) Biochem. J. 175, 1023-1032]. We have purified a trimer of actin monomers as well as a dimer and a mixture of higher molecular weight oligomers. The trimer is much more effective than the dimer in enhancing the rate of polymerization while higher oligomers do not appear to be any more effective than the trimer. A lag in the polymerization process, as measured fluorescence enhancement of trace pyrene-actin, still occurs in the presence of trimers serving as the nuclei, suggesting that the mechanism for polymerization is more complex than nucleation followed by elongation.