ABSTRACT
Providing excellent hearing in noise continues to be a major challenge for hearing aid designers and dispensers. At this time, the physiological and psychoacoustic mechanisms that make listening in noise difficult for persons with hearing loss are not completely understood. Among the many ``noise reduction'' methods that have been incorporated in hearing aids, the use of directional microphones is one of the few that imrpove signal-to-noise ratio. Directional microphones are effective in in the ear (ITE) and will be in the canal (ITC) hearing aids as well. Several currently-marketed digital signal processing (DSP) hearing aids have a variation of a noise reduction algorithm used in the 1980s. In studies of speech recognition in noise performance with these algorithms, results overall so far have been about the same as for sophisticated analog hearing aids. However, incorporation of a directional microphone in DSP hearing aids considerably improves their performance. For the future, both adaptive- and fixed-beam higher order directional microphone arrays and spectral and temporal enhancements of speech will improve further the performance of hearing aid wearers in noise. For the clinician to evaluate the benefits of hearing aids realistically, both viable electroacoustic and behavioral tests methods must be developed.
KEYWORD
Compression - headroom - signal-to-noise ratio - directional - digital
