On Peripheral Processing in Human Hearing
It was confirmed, through the discovery of traveling waves along the basilar membrane, that most of the ear’s frequency selectivity is established peripherally, i.e. within the cochlea and without neural lateral inhibition, some very carefully collected physiological data (e.g. Sellick et al., 1982a) have recently revealed that the frequency selectivity of the basilar membrane is sharper than was previously assumed. These results also agree quite well with data based on psycho-acoustical and neurophysiological measurements. The latter data, however, are more level dependent. As summarized earlier (Zwicker, 1979) significant non-linearities are found in many psychoacoustical measurements, not only in ordinary masking. Examples include difference tone production, two-tone interaction, specific loudness, post-masking (Zwicker and Fasti, 1972) and overload protection (Zwicker and Hesse, 1983). Some of these nonlinearities have already been shown to be related (Zwicker, 1979) but the combination with frequency selectivity complicates the discussion, since the efficiency of networks composed of linear (frequency selective) and nonlinear parts depends strongly on the sequence of these parts. In order to understand and to model the auditory system it is therefore necessary to find out which of the nonlinearities are located peripherally and which after neural transduction. It has been shown (Zwicker, 1983a), that masking - at least for lower SPLs - is performed peripherally. The location of two other nonlinear effects, overload protection and post-masking, has not yet been determined. The two experiments described below are designed to investigate this question.
KeywordsPeri Dition Dallos
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