Tracing Distortion Product (DP) Waves in a Cochlear Model
Abstract
In many cases a cochlear model suffices to explain (by simulation) the properties of waves in the cochlea. This is not so in the case of a distortion product (DP) set up by presenting two primary tones to the cochlea. A threedimensional model predicts, apart from a DP wave traveling in the apical direction, a DP wave that travels from the region of overlap of the two tone patterns towards the stapes—setting the stapes in motion so as to produce an otoacoustic emission at the DP frequency. Experimental research has shown, however, that the actual DP wave in the cochlea appears to travel in the opposite direction, from near the stapes to the overlap region. This feature has been termed "inverted direction of wave propagation" (IDWP). The forward wave could result from an unknown process such as a "hidden source" near the stapes. In the present study we have disproved this notion, by using a onedimensional model of the cochlea. It is found that both reverse and forward waves are set up by the source of nonlinearity, in the same way as has been published in an earlier work. The present results reveal that IDWP in the data corresponds to the region where the DP wave, originally created as a reverse wave but reflected from the stapes, has received so much amplification that it starts to dominate over the reverse wave. Hence we conclude that IDWP in a onedimensional model is a direct manifestation of cochlear amplification.
 Publication:

What Fire is in Mine Ears: Progress in Auditory Biomechanics
 Pub Date:
 November 2011
 DOI:
 10.1063/1.3658148
 Bibcode:
 2011AIPC.1403..557D
 Keywords:

 acoustics;
 frequency measurement;
 acoustic impedance;
 differential equations;
 43.64.Ha;
 43.66.Fe;
 43.20.Rz;
 02.60.Lj;
 Acoustical properties of the outer ear;
 middleear mechanics and reflex;
 Discrimination: intensity and frequency;
 Steadystate radiation from sources impedance radiation patterns boundary element methods;
 Ordinary and partial differential equations;
 boundary value problems