Threshold measurements and gain prescription with a HighIy configurable digital hearing aid

Abstract

A portable digital signal processor (P-DSP) has been developed which can be programmed not only as a hearing aid but also as an audiometer. The purpose of the study reported here was to compare hearing threshold levels measured using the P-DSP and a conventional audiometer. Prescribed real-ear gains resulting from these two sets of results were compared. Finally, the performance of the two hearing aid fits was assessed using speech material. Thirteen subjects with sensorineural hearing loss took part in the study (four cochlear implant subjects with residual hearing in the non-implanted ear, and nine hearing-aid users). Results showed that mean hearing thresholds measured via the P-DSP were close (within 5 dB) to thresholds measured using the audiometer in the low to mid frequencies. The mean difference across frequencies in the NAL-revised prescribed gain for the hearing aid fits was small < 5 dB). Real-ear insertion gains (REIGs) for both fittings were close to the prescribed gain from 125 to 2000 Hz (mean difference: ± 5 dB). The overall speech performance results showed no significant differences between the fittings. However, in cases where the REIGs were adjusted (to achieve a closer match with the prescribed gain), subjects did significantly better than when the frequency response and gain were calculated based only on the measured hearing thresholds (mean difference: 4.18 percentage points).