Volume 103, Issue 5, May 1998
Index of content:
- SPEECH PRODUCTION 
103(1998); http://dx.doi.org/10.1121/1.422785View Description Hide Description
The purpose of the study was to examine the acoustic, aerodynamic, physiologic, and perceptual characteristics of modal and vocal fry production. Twenty normal speakers (10 males, 10 females) participated in the study. Speech material included four sustained vowels (/i/, /ɑ/, /æ/, /u/), and syllable strings of /pi/ repetitions produced in both modal and vocal fry registers. Acoustic data (fundamental frequency, jitter, shimmer, and signal-to-noise ratio),aerodynamic data (airflow and air pressure), and electroglottographic (EGG) data were obtained simultaneously. Results demonstrated considerable differences across voice parameters for the modal and vocal fry registers. Fundamental frequency was significantly lower in vocal fry than in modal register for both males and females, however, significant gender differences existed only in modal register. For both males and females, measurements of jitter and shimmer were significantly higher and signal to noise ratio was significantly lower in vocal fry. In addition, airflow rate in modal register was almost three times as high as the airflow rate in vocal fry register during sustained vowel production. During syllable string production, subglottal air pressure values in modal register were approximately 1.5 times higher than that in the vocal fry register. In general, these data emphasize that the aeromechanical mechanisms of vocal fold vibratory behavior are substantially different between modal and vocal fry registers. A model of vocal fry phonation is presented to account for the present results.
Automatic parametrization of differentiated glottal flow: Comparing methods by means of synthetic flow pulses103(1998); http://dx.doi.org/10.1121/1.422786View Description Hide Description
The automatic parametrization of the first derivative of glottal flow is studied. Representatives of the two types of methods used most often for parametrization were tested and compared. The chosen representatives are all based on the Liljencrants–Fant model. As numerous tests were needed for a detailed comparison of the methods, a novel evaluation procedure is used which consists of the following stages: (1) use the Liljencrants–Fant model to generate synthetic flow pulses; (2) estimate voice source parameters for these synthetic flow pulses; and (3) calculate the errors by comparing the estimated values with the input values of the parameters. This evaluation procedure revealed that in order to reduce the average error in the estimated voice source parameters, the estimation methods should be able to estimate noninteger values of these parameters. The proposed evaluation method was also used to study the influence of low-pass filtering on the estimated voice source parameters. It turned out that low-pass filtering causes an error in all estimated voice source parameters. On average, the smallest errors were found for a parametrization method in which a voice source model is fitted to the flow derivative, and in which the voice source model is low-pass filtered with the same filter as the flow derivative.