A Study on the Preferred Real-Ear Insertion Gain of Multi-Channel Hearing Aid for the Korean with Sensorineural Hearing Loss

Abstract

Purpose: This study aimed to compare the preferred real-ear insertion gain for Korean (PREIG-K) wearing multi-channel hearing aid with the National Acoustics Laboratories-Non-Linear version 2 (NAL-NL2; National Acoustic Laboratories) gains in order to develop Korean hearing aid fitting formula.Methods: A total of thirty one (62 ears) Korean hearing aid users were included in this study. All subjects wore in-the-canal or custom hearing aids in both ears. Individual hearing aid fitting procedures involved to adjust the gains for 50, 65, and 80 dB sound pressure level of speech across low, high, and wideband frequency bands based on participant’s subjective responses. In addition, only the high frequency bands of 1 kHz or more of the PREIG-K were re-adjusted to be the same as NAL-NL2 gain and then the word recognition scores (WRSs) were compared before and after the adjusting gain. Results: The results showed that the PREIG-K increased up to 1.5 kHz with the maximum amount, then the PREIG-K decreased across the frequencies. For all half octave frequencies, the PREIG-Ks were substantially less than the NAL-NL2. When the PREIG-K of high frequencies were re-adjusted same as the NAL-NL2 gains, the WRSs of the PREIG-K were not significantly different before and after gain adjustment. The slopes up to 1.5 kHz frequencies of the PREIG-K were steeper than the slopes of NAL-NL2 gain, however similar to the slope of manufactures’ fitting formulae.Conclusion: The development of an effective hearing aid fitting formula for improving the communication abilities of hearing-impaired Korean will require further experiments considering the language, physical characteristics, and word recognition used by Koreans.