Evaluation of Efferent Adaptation Using Contralateral Suppression of TEOAEs

Abstract

The purpose of the present study was to evaluate the relationship between (1) the duration of contralateral acoustic stimulus and the suppression of transient evoked otoacoustic emissions (TEOAEs), and (2) the baseline TEOAE amplitude and the degree of TEOAE suppression. TEOAE amplitudes were measured in 50 normal-hearing individuals in four conditions: once without any noise (baseline measurement); a second time after exposure to noise for 1 minute; a third time after 6 minutes of exposure to noise, and a fourth time, after exposure to noise for 11 minutes. Broadband noise was presented always to the contralateral ear at 50 dB SL. Results revealed a significant reduction in the magnitude of OAEs when noise was introduced. Magnitude of suppression reduced when broadband noise was continued to 6 minutes. There was no relationship between baseline amplitude of TEOAE and the degree of suppression. These results have important implications for understanding the physiology of the efferent auditory system, and more particularly, efferent inhibition.