RESEARCH AND DEVELOPMENT OF PRACTICAL HEARING AIDS FOR TELEPHONIC SPEECH WITH A SMALL NON-LINEAR DISTORTION

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To realize the single resonant analysis type hearing aid for telephonic speech by real-time processing, we tried to make a small DSP system, which is based on our system for research. Single resonant analysis (SRA) type hearing aid presents speech sounds with a small nonlinear distortion compared with other types of hearing aid, but it needs more complicated calculations than other types of hearing aids. The system for research has four DSP units to perform real-time calculation, and includes hardware for developing the algorisms for hearing aids. As the ability of one DSP improves very much these days, two DSPs at high speed (60 MFLOPS each) are used to build up compact hearing aid. And the software had fitted to new hardware. It proved to be able to reduce the volume of the hearing aid to 1/20 of research system. This size is small enough to place to the sides of a telephone. In the last part of this project, much improvement in DSP performance was reported, and one DSP hearing aid for telephonic speech can be developed for the field test of SRA type hearing aid near future. And the fitting programs also should be improved for practical tests by hearing impaired person.