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

This investigation measured the degree to which hearing aids degrade speech discrimination in noise. Ten normal-hearing subjects were tested for speech reception thresholds (SRT) in noise. The tests were repeated under two aided conditions: one used binaural behind-the-ear (BTE) aids, the other an experimental binaural high-fidelity aid fitted with in-the-ear transducers. To assess the loss of any directional cues under aided conditions, a test environment producing directional cues in both horizontal and vertical planes was employed. Results indicated a 3 dB deterioration of speech-to-noise ratio for frontal speech with the BTE aids. Despite this, mean SRTs, when averaged over several listening directions, differed by less than 1 dB from unaided levels under both aided conditions. This suggests that improvements in hearing aid fidelity and directional performance beyond that available in current BTE aids will do little to improve speech discrimination in noise, although other benefits may accrue.