Application of Cortical Processing Theory to Acoustical Analysis

This research proposal aims at formulating signal processing principles realized by the auditory system, in particular when the input signal is speech. Two specific aims are: (1) to model the role of the descending pathway in stabilizing AN representationsof speech sounds in degraded acoustic conditions. Current models of the auditory periphery are based upon the ascending pathway up through the AN. We propose to study the role of the descending pathway (mainly the MOC feedback mechanism), and itsinteraction with the ascending pathway, in processing speech; (2) to model post-AN functions (e.g., cortical processing) that play a role in robust extraction of important acoustic-phonemic cues from the AN firing patterns. A psychophysical approach todetermine phenomenological models of cortical processing of speech stimuli will be used. To achieve these goals we propose a program of research that combines analytical measurements of human speech discrimination and auditory modeling, all using the samedatabase of diagnostic speech materials. The speech material will be subjected to parametric modifications in the time and frequency dimensions, and/or degraded systematically by additive speech-shaped noise. The validity of proposed auditory model willtested by utilizing it as a front-end in machines specifically designed to mimic the corresponding psychophysical experiments. ▪ Revising models of auditory periphery by including the role of the descending pathway in stabilizing cochlear responseof speech sounds in degraded acoustic conditions.▪ Using a psychophysical approach to determine phenomenological models of cortical processing. These models will provide guidance to physiological studies of cortical processing.▪ A first step toward achieving long-term goals of obtaining reliable diagnostic assessment of speech intelligibility and improving the performance of automatic speech recognition systems in acoustically adverse conditions.