Evaluating Traveling Wave Characteristics in Man by an Active Nonlinear Cochlea Preprocessing Model

Abstract

Since the discovery of v. Békésy (1943) that frequency-place transformation in the cochlea of vertebrates is accomplished by traveling waves of the displacement of the basilar membrane, many experiments have been undertaken to add to the knowledge about the vibration patterns taking place in the inner ear. For almost three decades, the data elaborated post mortem in birds and vertebrates looking through a microscope by v.Békésy have been used to describe cochlea wave patterns at any sound level. Introducing the indirect, but much more sensitive Mössbauer probe new data from living animals could be obtained. Rhode (1971) was the first pointing to the level dependence of basilar membrane displacement. More data at even lower levels and smaller displacement values have been published meanwhile (for references see for example Patuzzi et al., 1984). The new animal data showed very clearly that the inner ear and its normal activity are very vulnerable. From this point of view it seems to be unlikely that equivalent data from humans may become available. The level dependent, i.e. nonlinear data of the traveling wave characteristics of man are, however, of great interest not only for the people working in physiology and psychology but also in ENT-departments. Therefore indirect methodes leading to the data of interest may be used in exchange. As mentioned earlier (Zwicker, 1983) oto-acoustic emissions (OAE’s) can be used as an effective tool to enlarge our knowledge about the inner ear’s signal processing especially at low and very low levels at which normal méthodes mostly fail.