Low-frequency response of hearing aids and judgments of aided speech quality

Connected discourse was processed by a master hearing aid via two channels that were independently adjusted to seven discrete settings of low-cutoff frequency. Signals were tape-recorded and played back in a paired-comparison format to 12 listeners with gradually sloping sensorineural hearing loss, who selected the speech channel preferred for its sound quality. Four experimental trials were administered, each of which consisted of 21 randomized paired conditions. Results across the four trials revealed high intersubject and intrasubject response agreement. Listeners indicated strong and systematic preferences for speech reproduced by circuitry having progressively extended low-frequency emphasis. Findings confirm earlier experimental observations that hearing-impaired listeners are capable of making repeatable paired-comparison preference judgments of the quality of hearing-aid processed speech. Additionally, results demonstrate definitively that low-cutoff frequency is sufficiently robust to be regarded as the probable source of a potent perceptual basis for such judgments. The clinical implication is that hearing-impaired listeners can be expected to exhibit strong preferences for the quality of speech reproduced by hearing aids having relatively extended low-frequency response.