Study of frequency-lowering functions in hearing aids.

Abstract

　The aim of this study was to compare the efficacy of frequency lowering (FL) among 3 different hearing aids with built-in FL functions, under the“off”/“on” condition. The evaluation was performed by determining the monosyllable intelligibility under speech-like noise and the impression of sentences. Frequency lowering techniques in hearing aids are often used for patients with high-frequency hearing loss. There are various FL techniques available in hearing aids, such as linear frequency transposition (LFT), non-linear frequency compression (NLFC), frequency translation (FTl), high-frequency speech feature replication, and so on. The subjects of this study were 14 persons with normal hearing and 4 patients with high-frequency hearing loss.

　In the 14 persons with normal hearing (simulated high-frequency hearing loss), the intelligibility scores obtained with LFT and NLFC under the“on” condition were significantly lower than those in the“off” condition. The impression of FL under the“on” condition was relatively poor as compared to that without hearing aids. While the scores of FL (LFT, NLFC and FTl) under the“on” condition were higher than those under the“off” condition in the 4 patients, the results of impression of FL varied among the FL techniques, regardless of whether FL was in the“off”/“on” condition.

　FL techniques are considered to improve speech perception of patients with high-frequency hearing loss.