A Dynamic Compressive Gammachirp Auditory Filterbank

Abstract—It is now common to use knowledge about human au-ditory processing in the development of audio signal processors. Until recently, however, such systems were limited by their lin-earity. The auditory filter system is known to be level-dependent as evidenced by psychophysical data on masking, compression, and two-tone suppression. However, there were no analysis/synthesis schemes with nonlinear filterbanks. This paper describe18300060s such a scheme based on the compressive gammachirp (cGC) audi-tory filter. It was developed to extend the gammatone filter concept to accommodate the changes in psychophysical filter shape that are observed to occur with changes in stimulus level in simultaneous, tone-in-noise masking. In models of simultaneous noise masking, the temporal dynamics of the filtering can be ignored. Analysis/ synthesis systems, however, are intended for use with speech sounds where the glottal cycle can be long with respect to auditory time constants, and so they require specification of the temporal dy-namics of auditory filter. In this paper, we describe a fast-acting level control circuit for the cGC filter and show how psychophys-ical data involving two-tone suppression and compression can be used to estimate the parameter values for this dynamic version of the cGC filter (referred to as the “dcGC ” filter). One important ad-vantage of analysis/synthesis systems with a dcGC filterbank is that they can inherit previously refined signal processing algorithms de-veloped with conventional short-time Fourier transforms (STFTs) and linear filterbanks. Index Terms—Compression, nonlinear analysis/synthesis au-ditory filterbank, simultaneous masking, speech processing, two-tone suppression. I