2025 Volume 71 Issue 4 Pages 167-177
The use of real ear measurements (REM) is recommended by European and U.S. guidelines for the adjustment of nonlinear hearing aids. This study examined three cases of moderate sensorineural hearing loss, in which hearing aids were adjusted to the NAL-NL2 prescription target using REM. Case 1 involved the readjustment of a previously used hearing aid, while Case 2 involved a patient with a very narrow dynamic range. The NAL-NL2 prescription aims to optimize speech intelligibility while maintaining the overall loudness at a comfortable level. By using REM to directly measure and adjust the sound pressure at the eardrum, complaints about loudness were reduced, enabling consistent hearing aid use. As a result, favorable hearing outcomes were achieved in Cases 1 and 2. However, in Case 3, with steeply sloping high-frequency hearing loss, the adjustment method yielded unsatisfactory results. The NAL-NL2 prescription tends to prescribe less gain in the low-frequency range in steeply sloping high-frequency sensorineural hearing loss, and this limitation could hinder improvements in speech intelligibility, especially in languages such as Japanese, where vowels (which are primarily low-frequency sounds) occur frequently.
