ASA 125th Meeting Ottawa 1993 May

3aPP1. Ontogeny of 2f1-f2 acoustic and cochlear microphonic distortion products.

Ming Zhang

Dept. of Speech Pathol. and Audiol., Univ. of Iowa, 100 WJSHC, Iowa City, IA 52242

Paul J. Abbas

Univ. of Iowa, 127 WJSHC, Iowa City, IA 52242

The development of the acoustic distortion product (ADP) and cochlear microphonic distortion product (CMDP) 2f1-f2 was studied in pigmented rats, beginning 10 days after birth (p10). Both the ADP and CMDP were measured as a function of stimulus frequency (1.04 to 10.24 kHz with an f2/f1 ratio of 1.25) and level (20 to 80 dB SPL). The onset of the ADP occurred first at f2=5.12 kHz (p11--13), then at higher and lower frequencies. The amplitude of the ADP also matured first at f2=5.12 kHz (p17--18). This result is similar to the earlier work [S. J. Norton et al., Hear. Res. 51, 73--92 (1991); C. M. Henley et al., Hear. Res. 43, 141--148 (1989); M. Lenoir and J.-L. Puel, Hear Res. 29, 265--271 (1987)]. The onset and maturation of the DMDP was similar to ADP's, except at lower frequencies where the CMDP developed somewhat earlier. There is a strong correlation in amplitudes of the ADPs and CMDPs across ages, consistent with the hypothesis that the ADP and CM DP may be linked to the same process [D. T. Kemp and A. M. Brown, Hear. Res. 13, 39--46 (1984)].