Abstract
This paper presents an alternative method for implementing a dynamic compressive gammachirp (dcGC) auditory filterbank. Instead of using a cascade of second-order sections, the new approach uses digital frequency warping to give the gammawarp filterbank. In the warped implementation, the unit delays in a conventional finite impulse-response (FIR) filter are replaced by first-order allpass filters. The set of warped FIR filter coefficients is constrained to be symmetrical, which results in a filter phase response that is identical for all filters in the filterbank. The dynamic variation in filter response is provided by interpolating the outputs of three linear filters adjusted for low-, medium-, and high-input signal levels. The gammawarp filterbank offers a substantial improvement in execution speed compared to previous dynamic gammachirp filter implementations. For a linear filterbank, the gammawarp execution time is comparable to that of a gammatone or linear second-order section gammachirp implementation for 32 bands, but there is a processing time advantage that increases as the number of bands is increased. For a dynamic compressive gammachirp filterbank, the gammawarp implementation is 27 to 47 times faster than the dcGC MATLAB code of Irino.
Published Version
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