Volume 119, Issue 5, May 2006
Index of content:
- SPEECH PRODUCTION 
Numerical study of the effects of inferior and superior vocal fold surface angles on vocal fold pressure distributions119(2006); http://dx.doi.org/10.1121/1.2186548View Description Hide Description
Vocal fold geometry plays an important role in human phonation. A wide range of inferior and superior vocal foldsurface angles has been shown to be present during phonation [Nanayakkara, Master’s thesis, Bowling Green State University, Bowling Green, OH (2005)]. This study explored how these angles affect pressure distributions on the vocal folds, and thus how they may affect phonation. The computational code FLUENT was used to obtain pressure distributions for laminar, incompressible flow. Eighteen inferior vocal foldsurface angles and nineteen superior vocal foldsurface angles were selected for three specific glottal angles, uniform 0°, convergent 10°, and divergent 10°. Minimal glottal diameter , transglottal pressure , and glottal entrance radius were held constant, and the glottal exit radius was constant for each glottal angle. Results suggest that the vocal foldsurfacepressures are independent of the inferior and superior vocal foldsurface angles realistic for human phonation. These results suggest that, in contrast to the important effects of glottal entrance and exit radii, minimal diameter, and angle on intraglottal pressures, the inferior and superior vocal foldsurface angles (excluding possible interactive effects with the false vocal folds) do not have an influence on the intraglottal pressures.
119(2006); http://dx.doi.org/10.1121/1.2186429View Description Hide Description
The production of voice is related to the flow of air through the glottis, whose time-dependent shape is defined by the motion of the vocal folds and the translaryngeal pressure. A scaled dynamically similar experimental apparatus that mimics the motion of the vocal folds was designed and built, such that both the glottal diameter and glottal angle change during a motion cycle. This motion is more realistic than in other reported dynamic models. The motion of the folds can be driven at different frequencies. The glottalflow takes place at a constant inlet pressure, mimicking the lungpressure. The transglottal pressure difference and flow rate were measured over the motion cycle. Satisfactory agreement was obtained for identical cases by numerically solving the two-dimensional, incompressible Navier-Stokes equations. Both experimental and numerical data showed that the glottalflow rate and transglottal pressure were affected by the oscillation frequency of the vocal folds. Flow visualization showed that the glottalflow patterns, which are a potential source of aero-acoustic sound, are influenced by the oscillation frequency. However, glottalflow resistance depended to a lesser extent on vocal fold oscillation frequency for the portion of the cycle when the glottis was divergent.
119(2006); http://dx.doi.org/10.1121/1.2184226View Description Hide Description
The present study examined several potential distinctiveness-enhancing correlates of vowels produced in utterance focus by talkers of American English, French, and German. These correlates included possible increases in vowel space size, in formant movement within individual vowels, and in duration variance among vowels. Each language group enhanced the distinctiveness of vowels in context but used somewhat differing means to achieve this. All three groups used spectral differences, but only German talkers used durational differences, to enhance distinctiveness. The results suggest that the amount of distinctiveness enhancement of a vowel property in context is positively related to the between-category variation of that property in context. Thus, consistent with the theory of adaptive dispersion, utterance clarity appears to vary directly with information content.
119(2006); http://dx.doi.org/10.1121/1.2179657View Description Hide Description
For over half a century, musicologists and linguists have suggested that the prosody of a culture’s native language is reflected in the rhythms and melodies of its instrumental music. Testing this idea requires quantitative methods for comparing musical and spoken rhythm and melody. This study applies such methods to the speech and music of England and France. The results reveal that music reflects patterns of durational contrast between successive vowels in spoken sentences, as well as patterns of pitch interval variability in speech. The methods presented here are suitable for studying speech-music relations in a broad range of cultures.
Language redundancy predicts syllabic duration and the spectral characteristics of vocalic syllable nuclei119(2006); http://dx.doi.org/10.1121/1.2188331View Description Hide Description
The language redundancy of a syllable, measured by its predictability given its context and inherent frequency, has been shown to have a strong inverse relationship with syllabic duration. This relationship is predicted by the smooth signal redundancy hypothesis, which proposes that robust communication in a noisy environment can be achieved with an inverse relationship between language redundancy and the predictability given acoustic observations (acoustic redundancy). A general version of the hypothesis predicts similar relationships between the spectral characteristics of speech and language redundancy. However, investigating this claim is hampered by difficulties in measuring the spectral characteristics of speech within large conversational corpora, and difficulties in forming models of acoustic redundancy based on these spectral characteristics. This paper addresses these difficulties by testing the smooth signal redundancy hypothesis with a very high-quality corpus collected for speech synthesis, and presents both durational and spectral data from vowel nuclei on a vowel-by-vowel basis. Results confirm the duration/ language redundancy results achieved in previous work, and show a significant relationship between language redundancy factors and the first two formants, although these results vary considerably by vowel. In general, however, vowels show increased centralization with increased language redundancy.