Real-Time Gammatone Filterbank Spectography

Abstract

Speech scientists make extensive uSe of the spectrograph in their laboratory work. Conventional spectrographs produce an energy/frequency/time spectrogram of the input signal. based on the principle of a xed bandwidth lter oank analysis. Usually at least two lter bandwidth settings are available; a wide bandwidth to provide 'good' time response and a narrow bandwidth for good' frequency response. This paper discusses an initial implementation of a spectrograph system which models the human peripheral hearing system as a bank of GammaTone lters with bandwidths detemtined on an equivalent rectangular bandwidth (ERB) scale. The bandwidth of ERB-based analysis lters increases with frequency; thus the human hearing system exhibits 'good' frequency response at low frequencies and 'good time response at high frequencies. This bank of lters operates in parallel in the model, and we have used transputers to implement a realtime waterfall display spectrograph based on ERB spaced GammaTone lters. The graphics output of the system is handled by a 3-D transputer graphics processor board developed at York.