Characterizing individual hearing loss using narrow-band loudness compensation
Loudness is one of the key factors related to overall satisfaction with hearing aids. Individual loudness functions can reliably be measured using categorical loudness scaling (CLS) without any training. Nevertheless, the use of loudness measurement like CLS is by far less common than use of audiometric thresholds to fit hearing aids, although loudness complaints are one of the most mentioned reasons for revisiting the hearing aid dispenser. A possible reason is that loudness measurements are typically conducted with monaural narrow-band signals while binaural broad-band signals as speech or environmental sounds are typical in daily life. This study investigated individual uncomfortable loudness levels (UCL) with a focus on monaural and binaural broad-band signals, as being more realistic compared to monaural narrow-band signals. Nine normal-hearing listeners served as a reference in this experiment. Six hearing-impaired listeners with similar audiograms were aided with a simulated hearing aid, adjusted to compensate the narrow-band loudness perception back to normal. As desired, monaural narrow-band UCLs were restored to normal, however large individual deviations of more than 30 dB were found for the binaural broad-band signal. Results suggest that broad-band and binaural loudness measurements add key information about the individual hearing loss beyond the audiogram.