Voicing control in stop consonants has often been measured by means of voice onset time (VOT) and discussed in terms of interarticulator timing. However, control of voicing also involves details of laryngeal setting and management of sub- and supraglottal pressure levels, and many of these factors are known to undergo developmental change. Mechanical and aerodynamic conditions at the glottis may therefore vary considerably in normal populations as functions of age and/or sex. The current study collected oral airflow, intraoral pressure, and acoustic signals from normal English-speaking adults and children producing stop consonants and /h/ embedded in a short carrier utterance. Measures were made of stop VOTs, /h/ voicing and flow characteristics, and subglottal pressure during /p/ closures. Clear age and gender effects were observed for /h/: Fully voiced /h/ was most common in men, and /h/ voicing and flow data showed the highest variability among the 5-year-olds. For individual participants, distributional measures of VOT in /p t/ were correlated with distributional measures of voicing in /h/. The data indicate that one cannot assume comparable laryngeal conditions across speaker groups. This, in turn, implies that VOT acquisition in children cannot be interpreted purely in terms of developing interarticulator timing control, but must also reflect growing mastery over voicing itself. Further, differences in laryngeal structure and aerodynamic quantities may require men and women to adopt somewhat different strategies for achieving distinctive consonantal voicing contrasts.

In this study we use a low-dimensional laryngeal model to reproduce temporal variations in oral airflow produced by speakers in the vicinity of an abduction gesture. It attempts to characterize these temporal patterns in terms of biomechanical parameters such as glottal area, vocal fold stiffness, subglottal pressure, and gender differences in laryngeal dimensions. A two-mass model of the vocal folds coupled to a two-tube approximation of the vocal tract is fitted to oral airflow records measured in men and women during the production of /aha/ utterances, using the subglottal pressure, glottal width, and Q factor as control parameters. The results show that the model is capable of reproducing the airflow records with good approximation. A nonlinear damping characteristics is needed, to reproduce the flow variation at glottal abduction. Devoicing is achieved by the combined action of vocal fold abduction, the decrease of subglottal pressure, and the increase of vocal fold tension. In general, the female larynx has a more restricted region of vocal fold oscillation than the male one. This would explain the more frequent devoicing in glottal abduction-adduction gestures for /h/ in running speech by women, compared to men.

This study investigates token-to-token variability in fricative production of 5 year olds, 10 year olds, and adults. Previous studies have reported higher intrasubject variability in children than adults, in speech as well as nonspeech tasks, but authors have disagreed on the causes and implications of this finding. The current work assessed the characteristics of age-related variability across articulators ͑larynx and tongue͒ as well as in temporal versus spatial domains. Oral airflow signals, which reflect changes in both laryngeal and supralaryngeal apertures, were obtained for multiple productions of /h s z/. The data were processed using functional data analysis, which provides a means of obtaining relatively independent indices of amplitude and temporal ͑phasing͒ variability. Consistent with past work, both temporal and amplitude variabilities were higher in children than adults, but the temporal indices were generally less adultlike than the amplitude indices for both groups of children. Quantitative and qualitative analyses showed considerable speaker-and consonant-specific patterns of variability. The data indicate that variability in /s/ may represent laryngeal as well as supralaryngeal control and further that a simple random noise factor, higher in children than in adults, is insufficient to explain developmental differences in speech production variability.

Purpose To introduce theoretically-driven acoustic measures of /s/ that reflect aerodynamic and articulatory conditions. The measures were evaluated by assessing whether they revealed expected changes over time and labiality effects, along with possible gender differences suggested by past work. Method Productions of /s/ were extracted from various speaking tasks from typically-speaking adolescents (6 boys; 6 girls). Measures were made of relative spectral energies in low- (550–3000 Hz), mid- (3000–7000 Hz), and high-frequency regions (7000–11025 Hz); the mid-frequency amplitude peak; and temporal changes in these parameters. Spectral moments were also obtained to permit comparison with existing work. Results Spectral balance measures in low–mid and mid–high frequency bands varied over the time course of /s/, capturing the development of sibilance at mid-fricative along with showing some effects of gender and labiality. The mid-frequency spectral peak was significantly higher in non-labial contexts, and in girls. Temporal variation in the mid-frequency peak differentiated ±labial contexts while normalizing over gender. Discussion The measures showed expected patterns, supporting their validity. Comparison of these data with studies of adults suggests some developmental patterns that call for further study. The measures may also serve to differentiate some cases of typical and misarticulated /s/.