Volume 106, Issue 3, September 1999
Index of content:
- SPEECH PRODUCTION 
106(1999); http://dx.doi.org/10.1121/1.427148View Description Hide Description
Magnetic resonance imaging was used to quantify the vocal tract morphology of 129 normal humans, aged 2–25 years. Morphometric data, including midsagittal vocal tract length, shape, and proportions, were collected using computer graphic techniques. There was a significant positive correlation between vocal tract length and body size (either height or weight). The data also reveal clear differences in male and female vocal tract morphology, including changes in overall vocal tract length and the relative proportions of the oral and pharyngeal cavity. These sex differences are not evident in children, but arise at puberty, suggesting that they are part of the vocal remodeling process that occurs during puberty in males. These findings have implications for speech recognition,speechforensics, and the evolution of the human speech production system, and provide a normative standard for future studies of human vocal tract morphology and development.
On pitch jumps between chest and falsetto registers in voice: Data from living and excised human larynges106(1999); http://dx.doi.org/10.1121/1.427149View Description Hide Description
The paper offers a new concept of studying abrupt chest–falsetto register transitions (jumps) based on the theory of nonlinear dynamics. The jumps were studied in an excised human larynx and in three living subjects (one female and two male). Data from the excised larynx revealed that a small and gradual change in tension of the vocal folds can cause an abrupt change of register and pitch. This gives evidence that the register jumps are manifestations of bifurcations in the vocal-fold vibratory mechanism. A hysteresis was observed; the upward register jump occurred at higher pitches and tensions than the downward jump. Due to the hysteresis, the chest and falsetto registers can be produced with practically identical laryngeal adjustments within a certain range of longitudinal tensions. The magnitude of the frequency jump was measured as the “leap ratio” (fundamental frequency of the falsetto related to that of the chest register) and alternatively expressed as a corresponding musical interval, termed the “leap interval.” Ranges of this leap interval were found to be different for the three living subjects (0–5 semitones for the female, 5–10 and 10–17 for the two males, respectively). These differences are considered to reflect different biomechanical properties of the vocal folds of the examined subjects. A small magnitude of the leap interval was associated with a smooth chest–falsetto transition in the female subject.
106(1999); http://dx.doi.org/10.1121/1.427150View Description Hide Description
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 /ɑ/ 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.
106(1999); http://dx.doi.org/10.1121/1.427151View Description Hide Description
This study develops the notion of the “segmental anchoring” of movements, specifically, the finding that both the beginning and the end of a rising pitch accent are anchored to specific points in segmental structure [Arvaniti et al., J. Phonetics26, 3–25 (1998)]. If there are segmental anchors for rising accents (and if, as shown by Arvaniti et al., the level of the beginning and ending points is unaffected by the experimental manipulations), the anchors should be closer together as the speaking rate increases, and the rises should therefore be shorter and steeper. This was tested in two experiments in which speakers were asked to modify rate. The first experiment confirmed the basic prediction that the duration of accentual rises is affected by changes in rate. The second experiment studied the alignment of the beginning and ending points with their hypothesized segmental anchors. For all speakers there was a strong correlation between the duration of the rise and the time interval between the anchors, but only small and inconsistent effects of rate on alignment. Effects of rate on excursion size were likewise small and inconsistent. The results support a model in which pitch accents consist of “tonal targets,” and in which the alignment and level of tonal targets are what determine a pitch accent’s shape.