Arbeitsgruppe Medizinische Phys., Fachbereich Phys., Carl von Ossietzky Univ., D-26111 Oldenburg, Germany
In noisy and reverberant acoustical environments the human hearing system is capable of concentrating on a desired speaker, while attenuating undesired sounds like noise or reverberation. This so called ``cocktail-party processing'' is reduced in hearing-impaired persons. New hearing aid strategies try to imitate binaural processing principles to suppress interfering noise or reverberation in order to yield maximum speech intelligibility for the impaired listener. Two algorithms are described that reduce unwanted signal energies by attenuating sound that arises from the sides (lateral suppression) and that remove reverberation and short reflections. They were combined and implemented in real time on a multiprocessor setup to allow for adaptive adjustment of parameters and an optimal fit to the individual hearing loss. The noise reduction performance of the algorithms was tested with normal- and hearing-impaired subjects. Subjective speech quality and speech intelligibility assessments as well as speech intelligibility measurements show that both groups benefit significantly from the preprocessing strategies in anechoic and reverberant acoustical situations with interfering speakers.