Effects of release time and directionality on unilateral and bilateral hearing aid fittings in complex sound fields.

In studies to date, the effectiveness of the directional microphone has been investigated independently of the signal processing scheme used in the hearing aid. In addition, the number and placement of the background noise speakers can create an advantage for a particular polar pattern (i.e., cardioid, supercardioid, and hypercardioid) in any laboratory design. With these considerations in mind, the purpose of this investigation was twofold: (1) to determine the effect of different amplitude-compression release times on speech perception ability in noise, measured with directional microphone hearing aids, and (2) to determine the impact of environment (classroom vs anechoic chamber) on those measures. Ten subjects with mild to moderate sensorineural hearing loss participated. Using an eight-speaker complex sound field, speech perception was assessed in an anechoic chamber and a typical classroom environment. None of the release times resulted in superior performance in either the anechoic or classroom environment.