Intracochlear evidence on generation and propagation of distortion product otoacoustic emissions in gerbil cochlea

Abstract

Otoacoustic emissions (OAEs, Kemp, 1978) are complex signals appearing as a sum of multiple components relating to different cochlear source regions and different active mechanisms thus making it difficult to ascribe them to specific hearing frequencies. Improving the utility of OAEs requires understanding the origin of these multiple components and extracting the information they carry to the ear canal. The current presentation aims to provide direct intracochlear observations on OAE generation and their transmission. Two- or three-tone evoked pressure responses were simultaneously measured in the gerbil ear canal and scala tympani. Distortion product otoacoustic emissions (DPOAEs) and their intracochlear sources as DPs were analyzed. Results demonstrated: 1) DPOAEs come mainly from the f2 peak region, and extend further basal with increases in primary-tone intensities. These findings are consistent with several notions including: the theoretical prediction of “wave-fixed” or nonlinear generation, and th...