Effect of contralateral masking on the latency of otoacoustic emissions elicited by acoustic distortion products

Abstract

Otoacoustic emissions (OAE) are sound products generated by the outer hair cells (OHC) in the inner ear. The OHC are capable of moving spontaneously or in response to acoustic stimuli (spontaneous otoacoustic emissions and evoked otoacoustic emissions), these movements are known as electromotility. Electromotility is affected when contralateral acoustic stimulation is introduced to the ear. Different types of stimuli may produce this response. Clicks, pure tones, and white masking noise have been used as contralateral stimulation. This effect appears to be mediated by the medial efferent olivocochlear bundle. Contralateral masking produces suppression of OAE, especially on the amplitude. However, the effect of contralateral masking on the latency of distortion product otoacoustic emissions (DPOAE) has not been studied. The purpose of this paper is to investigate whether contralateral masking, with wide band masking noise, may produce a significant change on the latency of the DPOAE. Three different latency measurements of DPOAE measurements were made on low, middle and high frequencies of f1 including 574 Hz, 2454 Hz and 4919 Hz. Each one of these frequencies was measured with and without contralateral masking. Twenty-eight ears of 15 subjects were studied. Non-significant differences ( P>0.05) between masked and unmasked conditions were found in all cases. It is concluded that contralateral masking does not appear to affect latency of DPOAE.