Although the rounded-exponential (roex) filter has been successfully
used to represent the magnitude response of the auditory filter, recent
studies with the roex(p,w,t) filter reveal two serious problems: the
fits to notched-noise masking data are somewhat unstable unless the
filter is reduced to a physically unrealizable form, and there is no
time-domain version of the roex(p,w,t) filter to support modeling of the
perception of complex sounds. This paper describes a compressive,
gammachirp (cGC) filter with the same architecture as the roex(p,w,t)
which could be implemented in the time domain. The gain and asymmetry of
this parallel cGC filter are shown to be comparable to those of the
roex(p,w,t) filter, but the fits to masking data are still somewhat
unstable. The roex(p,w,t) and parallel cGC filters were also compared
with the cascade cGC filter [Patterson et al., J. Acoust. Soc. Am. 114,
1529-1542 (2003)], which was found to provide an equivalent fit with 25%
fewer coefficients. Moreover, the fits were stable. The advantage of the
cascade cGC filter appears to derive from its parsimonious
representation of the high-frequency side of the filter. We conclude
that cGC filters offer better prospects than roex filters for the
representation of the auditory filter.
Keywords: filter architecture, compressive gammachirp, parallel roex
filter, simultaneous masking
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