Time-interval information in the auditory representation of speech sounds

Abstract

In the auditory system, the primary fibers that encode mechanical motion of the basilar partition are phase-locked to that motion, and this information is preserved, to varying degrees, up to the inferior colliculus. It is known that this timing-interval information is used in localization, and it is probably also used to separate sources from diffuse background noise. The time intervals are on the order of milliseconds, and so traditional speech preprocessors (like MFCC systems) with frames on the order of 15 ms, remove the time-interval information from the representation. The performance of these systems deteriorates badly when the speaker is in a noisy environment. This suggests that time-interval processing will eventually need to be integrated into speech recognition systems if they are to achieve the kind of noise resistance characteristic of human speech recognition. An auditory image model (AIM) will be presented that is designed to stabilize repeating time-interval patterns like those produced by voiced speech, and results from experiments where AIM has been used as a preprocessor for automatic speech recognition. [Work supported by UK MRC (G9703469).]