A computational model for the peripheral auditory system: Application of speech recognition research

A computer system for speech analysis based on human auditory processing is described. The system consists of a bank of 40 independent channels, spanning the frequency range from 130 to 6400 Hz. Each channel includes a linear critical band filter followed by a model for the transformation from basilar membrane motion to nerve fiber response, incorporating such nonlinear effects as half-wave rectification, adaptation, spontaneous response, and saturation. The output of this stage includes the detailed waveshape of each cycle of the probabilistic response, but the data are never reduced to a spike sequence. Finally, each channel is subjected independently to both envelope detection and synchrony detection, where the latter is tuned to the characteristic frequency [CF] of the associated filter. It is likely that the envelope response will be useful for marking acoustic boundaries and for making broad category decisions, whereas the synchronous response is more appropriate for making fine distinctions.