Relationship between in-situ distortion and hearing aid benefit

In-situ hearing aid distortion is defined as distortion measured in the ear canal with stimulus inputs and hearing aid settings that are similar to those the hearing aid wearer will experience in daily life. This preliminary study examined possible relationships between in-situ distortion and benefit for appropriately fitted contemporary hearing aids. Simulated in-situ distortion was determined for 97 hearing aid fittings, divided among three typical listening environments: living room, classroom lecture, and social event. Measures included intermodulation, harmonic, and transient distortion. Overall results of between- and within-subject analyses of data suggested that there was a significant relationship between distortion and benefit in both reverberant and noisy environments similar to a classroom lecture and a social event, respectively. This outcome was seen despite the fact that distortion was quite low in absolute terms. Analyses also suggested that in-situ harmonic distortion was most closely related to benefit and that the other types of distortion measured did not make additional contributions to benefit prediction. We propose that measurements of in-situ harmonic distortion might be a valuable addition to hearing aid evaluations.