This research is directed toward improved signal-processing schemes to aid people with sensorineural hearing impairments. We intend either to develop improved schemes or to obtain a fundamental understanding of why such schemes cannot be developed. The proposed work includes study of linear amplification, amplitude compression, and frequency lowering. Also, attempts will be made to determine and understand the effects of variations in speech production on speech reception by impaired listeners. The research on linear amplification is concerned with modelling the dependence of speech-reception performance on the speech materials, the background interference, the listener, and the linear amplification system. Initial work on this project involves an attempt to apply Articulation Theory to speech reception by impaired listeners. The research on amplitude compression, directed towards listeners with reduced dynamic range, involves further study of multiband syllabic compression, as well as study of automatic volume control and limiting. The research on frequency lowering, directed towards listeners with poor hearing at high frequencies, continues to focus on pitch-invariant, nonuniform lowering. In both areas, the proposed work involves further exploration of the effects of various system parameters on speech-reception performance, testing of a wider variety of subjects, and attempts to determine the underlying causes of the results obtained. The research on the effects of variations in speech production is motivated by our belief that there exist variations, both intersubject and intrasubject, that lead to substantially improved speech reception, and that an understanding of these variations and their effects will provide useful background for the development of improved signal-processing schemes. The proposed work in this area involves the development of speech materials uttered by different speakers under a variety of speaking conditions, the measurement of speech reception by impaired listeners using these materials under a variety of listening conditions, and the attempt to correlate the speech-reception results with properties of the acoustic waveforms.
