Objective measure of low-frequency amplification reduction in canal hearing aids with adaptive circuitry.

The total amount of "ampclusion" (low-frequency amplification + occlusion) and its reduction were measured in two identically fitting canal hearing aids with three circuitry capabilities: (1) K-Amp, (2) linear, and (3) noise reduction (ANP II). The insertion gains of all three circuits were adjusted to be closely matched and the amounts of occlusion for both aids were almost identical. Real-ear measurements were obtained as the author vocalized the phoneme /i/ at 65 dB SPL at 2 ft in three conditions: (1) unoccluded, (2) occluded, aid off, and (3) occluded, aid on. The results indicated a reduction in the low-frequency amplification component of ampclusion for both adaptive circuits when compared to the linear circuit, with the K-Amp showing slightly greater reduction than the ANP II. These findings suggest that in addition to noise-reduction circuitry, K-Amp circuitry will also provide a more pleasant experience to the hearing aid wearer when listening to his/her own voice.