Cochlear nonlinearity and second filter: Possible mechanism and implications

Abstract

We indicate that the directional sensitivity of the hair cell together with a directional distribution of frequency over the hair cells comprise a possible physiological basis for the second filter. Tuning disparity of the first and second filter denotes the difference in tuning frequency; at a given position x the tuning frequency of the first filter is αCF, of the second CF, with α≳1. This accounts for the asymmetry in location of two-tone suppression areas. The compressive nonlinearity is described by a νth law device with ν<1. We analyze implications of this model for two-tone suppression, sharpening, pure-tone masking, and combination tone generation. Basic features of these phenomena are described adequately. For combination tones the propagation problem needs further study. On the basis of a comparison of literature data and theoretical predictions we estimate α=1.2 and ν=0.6. Regarding accurate shape of the first and second filter, the discussed data provide means for a qualitative evaluation only. Possibilities for a quantitative analysis are indicated.Subject Classification: [43]65.20, [43]65.35, [43]65.42, [43]65.26.