The goal of this work is to develop a multiple modality assistive listening device which assists hearing impaired individuals to understand speech in high ambient noise level environments. Two important issues are; that the design include a noise resistant microphone as a primary input device; and that it be configurable at the users option for use with other existing ALD transmission types (FM, IR and induction). Since the goal is to assist two different hearing impaired populations, hearing aid users and non-hearing aid users, two different system configurations will be required for the device to accommodate different use requirements. In both configurations the system will be designed such that a user can purchase a basic unit and add an additional input mode and/or interface capability for additional transmission types if his needs change. This present work will focus a compact short range IR transmitter/receiver and selecting optimum interface techniques for other ALD modes. In spite of many years of research, present noise reduction techniques applied for hearing aids and ALDs are poor when inputs are derived from microphones in high ambient noise situations. The technique for obtaining noise immunity to be developed in this work, applicable to ALD's and probably to hearing aids as well, appears to be very powerful and able to obtain significant noise immunity in a very simple manner.
