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.

This study investigates token-to-token variability in fricative production of 5year olds, 10year 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 tongue) 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 (phasing) 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: This article introduces 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 nonlabial contexts, and in girls. Temporal variation in the mid-frequency peak differentiated ±labial contexts while normalizing over gender.Conclusions: 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/.

Numerous researchers have measured voice onset time (VOT) in children. Authors attempting to trace developmental trends in consonant voicing have frequently framed their hypotheses in terms of how children's VOT means and/or standard deviations compare to adult norms. However, data from previous studies suggest that children's VOTs may not be normally distributed. Specifically, rightward skew is observed in the voiceless aspirated stops, such that mean values exceed the medians. The current work presents detailed distributional analyses of VOTs in /p, t/ from 7 five-year-old children and 14 adults. Distributional non-normality was common in both the adult and child data, as measured by Shapiro and Wilk's W statistic. The children showed an insignificant but consistent tendency towards higher values of skew than the adults and greater differences between VOT mean and median values. The results suggest that theories of VOT development should not be based solely on means and standard deviations, but need to address the distributional characteristics of the data more fully.

Previous authors have established that stop consonant voicing is more limited in young children than adults, and have ascribed this to immature vocal-tract pressure management. Physical development relevant to speech aerodynamics continues into adolescence, suggesting that consonant voicing development may also persist into the school-age years. This study explored the relationship between stop consonant voicing and intraoral pressure contours in women, $5\text{year}$ olds, and $10\text{year}$ olds. Productions of intervocalic /p b/ were recorded from eight speakers at each age. Measures were made of stop consonant voicing and $\delta$ , a measure designed to characterize the time course of intraoral pressure increase in stops, following Müller and Brown [Speech and Language: Advances in Basic Research and Practice, edited by N. Lass (Academic, Madison, 1980), Vol. 4, pp. 318–389]. Age effects for stop consonant voicing and $\delta$ were not statistically significant, but correlations between $\delta$ and stop voicing were less often significant and sometimes reversed in the children, providing some evidence of immature aerodynamic control. The current data, as well as those of Müller and Brown, also show that the $\delta$ measure may yield some paradoxical values, indicating that more work is needed on methods of assessing time-varying characteristics of intraoral pressure.

In obstruent consonants, a major constriction in the upper vocal tract yields an increase in intraoral pressure (Pio). Phonation requires that subglottal pressure (Psub) exceed Pio by a threshold value, so as the transglottal pressure reaches the threshold, phonation will cease. This work investigates how Pio levels at phonation offset and onset vary before and after different German voiceless obstruents (stop, fricative, affricates, clusters), and with following high vs low vowels. Articulatory contacts, measured using electropalatography, were recorded simultaneously with Pio to clarify how supraglottal constrictions affect Pio. Effects of consonant type on phonation thresholds could be explained mainly in terms of the magnitude and timing of vocal-fold abduction. Phonation offset occurred at lower values of Pio before fricative-initial sequences than stop-initial sequences, and onset occurred at higher levels of Pio following the unaspirated stops of clusters compared to fricatives, affricates, and aspirated stops. The vowel effects were somewhat surprising: High vowels had an inhibitory effect at voicing offset (phonation ceasing at lower values of Pio) in short-duration consonant sequences, but a facilitating effect on phonation onset that was consistent across consonantal contexts. The vowel influences appear to reflect a combination of vocal-fold characteristics and vocal-tract impedance.