ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pPP62. Distortion product otoacoustic emissions created through the interaction of a spontaneous otoacoustic emission and an externally generated tone.

Linda W. Norrix

Theodore J. Glattke

Dept. of Speech & Hear. Sci., Univ. of Arizona, Tucson, AZ 85721

An SOAE (f[sub 2]) and one XT (f[sub 1]) were used to create 2 f[sub 1]-f[sub 2] DPOAEs. External tones were applied to the ear canal at SOAE/f[sub 1] ratios between 1.08 and 1.22 XT/SOAE intensity differences varied from 0 to approximately 50 dB SPL. DPOAE amplitude and SOAE suppression characteristics were variable across subjects. However, the following trends were noted: (1) At larger frequency ratios, DPOAE generation and SOAE suppression were associated with greater XT SPLs; (2) DPOAE growth functions were characterized by slopes <1 dB/dB, a maximum, rollover and disappearance into the noise floor; (3) maximum DPOAEs were observed at frequencies approximately 1/2 oct below the SOAEs; (4) DPOAE maximums were associated with a significant amount of SOAE suppression. The results are consistent with DPOAEs created using two low-level tones [Brown and Gaskill, in Mechanics and Biophysics of Hearing (Springer-Verlag, Berlin, 1990)] and can be interpreted by considering suppression in a nonlinear cochlear model [Zwicker, 163--176 (1986).] [Work supported by NIH-NIDCD grant 1 P60 DC-01409 and Univ. of AZ Graduate Student Development Fund.]