平原達也
A Computational Cochlear Nonlinear Preprocessing
Model with Adaptive Q Circuits
Abstract:A computational nonlinear cochlear filter model with adaptive
Q circuits is described. The model is build by introducing adaptive
Q circuits into the linear cascade/parallel cochlear filter-bank. The
adaptive Q circuit is composed of two part: a second order lowpass
function (LPF) and a Q decision circuit which calculates LPF's
Q in every time frame according to the input spectrum level. This
model functionally simulates three level. dependent characteristics
observed in the basilar membrane motion: level dependent
selectivity, level dependent sensitivity and level dependent
resonance frequency shift. The model output gives better internal
speech spectrum representation than those of a linear cochlear
filter-bank. Namely, (1) weak consonants and higher formants are
enhanced, (2) both the temporal and the harmonic structure are
consistent at the same time frame, and (3) the spectrum are
spread and enhanced where the spectrum changes abruptly.
These advantages, which are the phenomena observed in the real
auditory frequency analysis, support the effectiveness of the
model.