Elaine T. Stathopoulos

Formants of children, women, and men: The effects of vocal intensity variation

The purpose of this study was to investigate the formant frequencies and amplitudes of a wide age range of children and one group of adults at three sound pressure levels (SPLs). Subjects were ten females and ten males in the following age groups (in years): 4, 6, 8, 10, 12, 14, 16, 18, and adults. A sustained /a/ was produced three times by each subject. Formant frequencies were obtained using linear predictive coding analysis. Formant amplitudes were measured from the highest amplitude harmonic in the area of each formant. In addition to following established trends previously published in other studies, it was hypothesized that the first formant frequency would increase with increasing intensity, that females would have higher formant frequencies than same aged males, and that women and children would have reduced formant amplitudes as compared to men. It was found that first formant frequency increased with intensity and changed as a function of age and sex. Second and third formant frequencies changed with age and sex. Formant amplitudes followed the trends set by the SPL differences and did not change as a function of age and sex. Results are discussed in terms of anatomic differences and SPL.

Respiratory and laryngeal measures of children during vocal intensity variation

Simultaneous aerodynamic, acoustic, and kinematic measurements from the laryngeal and respiratory systems were made in order to study mechanisms for changing vocal intensity. Aerodynamic and acoustic measures include an approximation of open quotient, maximum flow declination rate, alternating glottal airflow, estimated tracheal pressure, sound pressure level, and fundamental frequency. Respiratory measures included lung volume, rib cage, and abdominal displacements. Adults were used as a comparison group to twenty 4-year-olds and twenty 8-year-olds. Laryngeal and respiratory results indicate that speech production differences between the children and adults are based both on size and function. For example, childrens absolute anteroposterior diameters of the rib cage are smaller than adults, but their rib cage movement is larger and encompasses a different range during speech breathing. Since children are functionally different than adults, age specific speech production models need to be developed.

Glottal airflow and electroglottographic measures of vocal function at multiple intensities

Summary Ten normal female subjects produced syllables at 5 dB increments from soft to loud. The differentiated electroglottogram (dEGG) open and speed quotients were compared to similar quotients from the inverse-filtered airflow waveform. The latter were measured according to objective and subjective criteria. The data indicate that the open quotient from the airflow waveform decreased as the intensity increased. The dEGG open quotient did not demonstrate this trend. The speed quotient from airflow increased initially with vocal intensity and decreased again as the intensity ceiling was approached. The ratio of closing to opening slopes calculated from peaks in the dEGG signal followed a similar pattern. While the trends across intensity conditions were found to correspond for several of the measures, the absolute values obtained using the different methodologies were not comparable.

Approximations of Open Quotient and Speed Quotient from Glottal Airflow and EGG Waveforms: Effects of Measurement Criteria and Sound Pressure Level

Noninvasive measures of vocal fold activity are useful for describing normal and disordered voice production. Measures of open and speed quotient from glottal airflow and electroglottographic (EGG) waveforms have been used to describe timing events associated with vocal fold vibration. To date, there has been little consistency in the measurement criteria used to calculate quotient values. In this study, criteria of 20% and 50% were applied to the AC amplitude of glottal airflow and inverted EGG waveforms for measurement of open quotient. Criteria of 20%, 50%, and 80%, and a midslope criterion that segmented the waveform between 20% and 80% of the waveform amplitude, were used for the calculation of speed quotient. Subjects produced waveforms at sound pressure levels (SPL) of 70, 75, 80 and 85 dB. Results indicated that approximations of open quotient obtained from the glottal airflow waveform significantly decreased using both the 20% and 50% criteria as SPL increased from 80 to 85 dB. No significant changes were found in open quotient from the EGG waveform as a function of SPL. Results of speed quotient measures from the glottal airflow and EGG waveforms showed a generally increasing trend as SPL increased, although the differences were not statistically significant. The data suggest that the signal type, measurement criterion and SPL must be considered in interpreting quotient measures.

Perceptual evaluation of Hypernasality compared to HONC measures: The role of experience

Objectives Nasality ratings from experienced and inexperienced listeners were compared to accelerometric measures using the Horii Oral Nasal Coupling (HONC) Index to determine if one groups ratings are more closely related to the HONC Index measures. The reliability of listener ratings was studied to determine if experienced listeners had better reliability than inexperienced listeners. The influence of phonetic content was analyzed to learn if ratings of sentences with stop consonants yielded higher correlations with HONC scores than sentences containing glides. Design Experienced and inexperienced listeners’ ratings of hypernasality were correlated to the HONC measures for two nonnasal sentence productions. Analysis of variance compared experienced versus inexperienced listener ratings. Participants Ten listeners who were speech-language pathologists with at least 10 years of experience in assessing hypernasality and 10 listeners who were graduate students in communicative disorders with less than 1 year of experience. Speech samples were acquired from 13 children with varying degrees of hypernasality and 5 children with normal nasality. Results Correlations between ratings of hypernasality and HONC scores were .60 for the experienced group and .52 for the inexperienced group. In general, the experienced listeners rated the hypernasality of the speakers as less severe. Both groups had similar intrajudge reliability. Hypernasality ratings were not influenced by sentence context. Conclusions Hypernasality can be rated in a reliable fashion regardless of listener experience. The correlations between the objective measure of nasalization (HONC) and the perceptual ratings were not as high as expected. Factors contributing to obtaining only moderate correlations will be discussed.

Vocal efficiency as a function of vocal intensity: A study of children, women, and men

The effect of vocal intensity on vocal efficiency (VE) for children as compared to adults is investigated, leading to the conclusion that children have different VE values than adults. Vocal efficiency was measured using a logarithmic form of the ratio of the acoustical power radiated from the lips to the aerodynamic power supplied to the glottis for voice production. Sixty subjects participated in this study, including 20 subjects with 10 males and 10 females in each of the three age groups: 4-year-olds, 8-year-olds, and adults. The speech tasks were produced at soft, comfortable, and loud levels, and the VE measurements were mathematically adjusted to account for the sound-pressure level variations within each intensity level among the subject groups. The VE values were compared for age, intensity, and gender differences. The results indicate that 4-year-olds and 8-year-olds have lower VE values than adults. Vocal efficiency increased with vocal intensity for all the age groups, and no significant differences were found for females as compared to males. Factors influencing VE such as maturation of the vocal ligament, amplitude of vocal fold vibration, fundamental frequency, tracheal pressure, as well as the source spectra are discussed.

Speech task effects on acoustic and aerodynamic measures of women with vocal nodules

Vowel prolongation is often used to evaluate disordered voice production. In light of previous findings showing that co-articulation has significant influence on laryngeal function measures, the practice of using prolonged vowels to represent a speech sample is questioned. To test whether disordered and normal voice during vowel production is generalizable to connected speech, three speaking tasks were investigated: sustained vowel prolongation, syllable repetition and reading. Statistical differences were found between these tasks for certain amplitude and time based laryngeal function measures for adult women with disordered and normal voice. However, for the specific measures which were statistically different, the actual numerical and perceptual differences may be quite small. From a clinical assessment standpoint, the choice of the speech task may not make an apparent difference in the objective evaluation of disordered voice.

Variability revisited: An acoustic, aerodynamic, and respiratory kinematic comparison of children and adults during speech

Abstract A review of the kinematic and acoustic literature fails to provideunequivocal support for the general assumption that the childs speech mechanism is more variable than the adults. The current study, applying a variety of coordinated acoustic and kinematic measures to children and adults ranging from 4 to 30 years, confirms that children are not consistently more variable. In particular, only the four-year-olds show some tendency to produce acoustic, aerodynamic, and respiratory kinematic speech events with more variability than adults. In some instances, adults displayed more variable speech behaviors than children. The author questions both the general assumption of linear development, and the “analytic components” approach to physiological modeling, suggesting rather that development may be multimodal, with different parts of the system developing at different rates at different times, and that a construction-theoretic approach to modeling may be useful.

Speech breathing during reading in women withvocal nodules

This study examined speech breathing patterns during reading by women with bilateral vocal fold nodules judged as mildly dysphonic and by women without vocal nodules. Although it might be predictable that the speech breathing patterns of individuals with laryngeal dysfunction will differ from those without laryngeal dysfunction, there is a lack of empirical data to support such assumptions. The results of the current study indicated that glottal airflow was greater during reading for the women with vocal nodules and that a larger volume of air was expended both per syllable and per breath group during reading. The rate of speech did not significantly differ between the two groups of women. There was no significant difference for the average duration of the breath groups and no significant difference for the number of syllables spoken per breath group. Additionally, both groups of women demonstrated a similar pattern of inspiratory pause location during the reading. The results suggest that speech breathing patterns associated with dysphonia be examined independently to distinguish specifically the nature of the interaction between the laryngeal dysfunction and the speech breathing pattern. Certainly, more information on how the severity of a voice disorder influences speech breathing is necessary.

Comparison of maximum flow declination rate: children versus adults

The measure of maximum flow declination rate (MFDR) and location of MFDR provided information regarding the laryngeal mechanisms response to vocal intensity variation as a function of gender and age. Results indicate (a) increases in MFDR values as vocal intensity increases for both children and adults, and (b) higher MFDR values for men versus women and children; no gender difference was found for the children. Results for location of MFDR indicate (a) the location of MFDR to be highest for the loud-intensity production as compared with soft- and comfortable-intensity productions, and (b) the location of MFDR in women to be higher than in men. No gender difference was found for the children.