ATR Human Information Res. Labs., 2-2 Hikaridai Seikacho Soraku-gun Kyoto 619-02, Japan
ATR Human Information Res. Labs., Kyoto, Japan
Univ. of Wisconsin, Madison, WI 53705-2280
The pyriform fossa consists of two bilateral cavities located behind the laryngeal ventricle. The fossa is known to act as a branch of the vocal tract by Fant's study (1960) based on x-ray data. This study investigates acoustic characteristics of the fossa using hardware models, which replicated the portion from the vocal folds to the velum based on volumetric MRI data, and using human subjects. Acoustic measurement was performed on the models by filling and emptying the fossa. The results confirmed that the fossa contributes local zeros to speech spectra at about 4 kHz. Further, it was shown that the effects of the fossa extend down to the first and second vowel formants. This global effect of the fossa on formant pattern has been confirmed by this simulation as being dependent on the location of the fossa close to the sound source. An in vivo experiment was performed by injecting water into the fossa of human subjects, and identified the antiresonance frequencies of the fossa as the frequencies increase with decreasing the volume. The zeros obtained from these experiments were found to be consistent with those in natural speech. The relatively stable acoustic properties are thought to provide one of the individual characteristics of speech sounds.