ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

5aSP2. The normal modes of incompressible vocal fold tissues.

David A. Berry

Ingo R. Titze

Natl. Ctr. for Voice and Speech, Dept. of Speech Pathol. and Audiol., Univ. of Iowa, Iowa City, IA 52242

Much of the theoretical groundwork for treating vocal fold vibrations as viscoelastic waves in a continuum can be found in earlier publications [Titze and Strong, J. Acoust. Soc. Am. 57, 736--744 (1975) and Titze, J. Acoust. Soc. Am. 60, 1366--1380 (1976)]. Both of these papers are based on small-amplitude vibrations where linearization is assumed to be valid, allowing normal modes and natural frequencies to be calculated. Although vocal fold tissues are known to be nearly incompressible, the first analytic expression for the normal modes of vocal fold tissues were based on the assumption of complete compressibility. The present study shows how the analytic normal modes deform and how the natural frequencies of oscillation shift as the vocal fold tissues are gradually changed from being strictly compressible to absolutely incompressible, leaving all other factors constant. [This research was supported by Grant No. P60 DC00976 from the National Institute on Deafness and Other Communication Disorders.]