Volume 115, Issue 3, March 2004
Index of content:
- SPEECH PRODUCTION 
115(2004); http://dx.doi.org/10.1121/1.1648974View Description Hide Description
A nonlinear model was proposed to study chaotic vibrations of vocal folds with a unilateral vocal polyp. The model study found that the vocal polyp affected glottal closure and caused aperiodic vocal fold vibrations. Using nonlinear dynamic methods, aperiodic vibrations of the vocal fold model with a polyp were attributed to low-dimensional chaos.Bifurcation diagrams showed that vocal polyp size, stiffness, and damping had important effects on vocal fold vibrations. An increase in polyp size tended to induce subharmonic patterns and chaos. This study provides a theoretical basis to model aperiodic vibrations of vocal folds with a laryngeal mass.
115(2004); http://dx.doi.org/10.1121/1.1646403View Description Hide Description
The audio signal from five professional baritones was analyzed by means of spectrum analysis. Each subject sang syllables [pæ] and [pa] from loudest to softest phonation at fundamental frequencies representing 25%, 50%, and 75% of his total range. Ten subglottal pressures, equidistantly spaced between highest and lowest, were selected for analysis along with the corresponding production of the vowels. The levels of the first formant and singer’s formant were measured as a function of subglottal pressure. Averaged across subjects, vowels, and a 10-dB increase at 600 Hz was accompanied by a 16-dB increase at 3 kHz.
115(2004); http://dx.doi.org/10.1121/1.1645248View Description Hide Description
The production of the lateral sounds involves airflow paths around the tongue produced by the laterally inward movement of the tongue toward the midsagittal plane. If contact is made with the palate, a closure is formed in the flow path along the midsagittal line. The effects of the lateral channels on the sound spectrum are not clear. In this study, a vocal-tract model with parallel lateral channels and a supralingual cavity was developed. Analysis shows that the lateral channels with dimensions derived from magnetic resonanceimages of an American English /l/ are able to produce a pole–zero pair in the frequency range of 2–5 kHz. This pole–zero pair, together with an additional pole–zero pair due to the supralingual cavity, results in a low-amplitude and relatively flat spectral shape in the frequency region of the /l/ sound spectrum.
115(2004); http://dx.doi.org/10.1121/1.1647145View Description Hide Description
While the Speech Transmission Index(STI) is widely applied for prediction of speech intelligibility in room acoustics and telecommunication engineering, it is unclear how to interpret STI values when non-native talkers or listeners are involved. Based on subjectively measured psychometric functions for sentence intelligibility in noise, for populations of native and non-native communicators, a correction function for the interpretation of the STI is derived. This function is applied to determine the appropriate STI ranges with qualification labels (“bad”–“excellent”), for specific populations of non-natives. The correction function is derived by relating the non-native psychometric function to the native psychometric function by a single parameter (ν). For listeners, the ν parameter is found to be highly correlated with linguistic entropy. It is shown that the proposed correction function is also valid for conditions featuring bandwidth limiting and reverberation.