Signal-to-Noise Ratio Advantage of Binaural Hearing Aids and Directional Microphones under Different Levels of Reverberation

Abstract

The signal-to-noise ratio necessary for a constant performance level was determined for normally hearing and hearing-impaired subjects under three levels of reverberation (0.3, 0.6, and 1.2 s) with monaural and binaural hearing aids having directional and omnidirectional microphones. Results indicated (a) a significant binaural advantage (2-3 dB) which was independent of microphone type and reverberation time, (b) a significant directional microphone advantage (3-4 dB) which was independent of hearing aid arrangement (monaural or binaural) but dependent on level of reverberation, (c) a significant reverberation effect which was larger than either the binaural or directional microphone effect, and (d) additive binaural and directional microphone advantages. The results suggest that the signal-to-noise ratio is optimized when binaural hearing aids with directional microphones are used in rooms with short reverberation times.

Unilateral Versus Bilateral Hearing Aid Fittings

“…This implied a significant advantage of bilateral over unilateral amplification, which proved to be dependent on the type of microphone (omni-directional or directional) and the azimuth of the noise source, except for 0 0 . Contrary to the results of Hawkins and Yacullo (1984), the bilateral advantage in speech intelligibility was highest with directional microphones. Dreschler and Boymans (1994) measured SRTs in noise with a spatial separation between speech and noise in 12 hearing-impaired subjects.…”

“…This suggests that contribution of the unaided ear was mainly responsible for the fact that the benefit from bilateral fitting depends on the degree of hearing loss. Hawkins and Yacullo (1984) determined the S/N ratio necessary for a constant performance level of word recognition for normal hearing and for hearing-impaired listeners with bilaterally symmetrical mild-to-moderate sloping sensorineural hearing losses. The showed a bilateral advantage (2-3 dB) and this appeared to be independent of microphone type and reverberation time.…”

Amplification and the Geriatric Patient

“…Binaural amplification provides the user with a 2-3 dB signal-to-noise ratio enhancement (31). It is critical to the success of the aural rehabilitation program to do everything possible to enhance the signal-to-noise ratio; hence, binaural amplification should be recommended and encouraged for most patients with presbycusis.…”

The effects of hearing aids on speech discrimination in noise by normal-hearinglisteners

“…The effects resulting from directional factors have not been as well-documented in the literature, although several researchers have investigated the influence of hearing aids on the ability to discriminate spatially separate signals located in the horizontal plane: e.g., Festen and Plomp (4), and Hawkins and Yacullo (6) . Their results indicate that hearing aids do little to lessen the advantage offered the unaided ear by spatially separate signals .…”