INTERACTIVE FITTINGS VERSUS PRESCRIPTIVE FITTINGS IN HEARING AIDS

Boymans M, Dreschler WA.

Academic Medical Center, Amsterdam, The Netherlands.

Background: There is no unequivocal way to fit modern hearing aids. After a “first-fit” of the hearing aid according to proprietary fitting rules a further fine tuning can be conducted either using in-situ measurements or using an interactive fitting procedure.

Aims: In this multicenter study interactive fittings (with the Amplifit® II system) were compared with prescriptive fittings (with insertion-gain measurements).

Methods: For the interactive fittings the hearing aid dispenser selected new hearing aids and video fragments which simulated daily life situations. After fitting the hearing aids (according the “first-fit”) the subject judged the video fragments and answered questions about speech intelligibility, listening comfort, and sound quality, corresponding to six acoustical dimensions. Based on the results, the hearing aid dispenser could fine tune the hearing aids. The results were compared with a hearing aid fitting based on insertion-gain measurements according the NAL-NL1 fitting rule.

Results: In a blinded cross-over design 73 subjects had a trial period of six weeks for each hearing aid fitting. The order of fittings was randomized. The fittings were evaluated objectively (insertion-gain measurements) and subjectively (by means of extensive questionnaires: SSQ and AVETA) after each trial period. The performance was evaluated by speech tests in quiet, continuous noise, and time reversed speech, both presented at 0 degrees and with spaciously separated sound sources. On average the prescriptive fittings resulted in higher gains and in better speech intelligibility, in quiet and in noise, than the interactive fittings.

Conclusions: The results show that the prescriptive method gives better speech intelligibility and can be regarded as an intelligibility driven approach. However, in the domain of subjective results other benefits were found for the interactive fitting. The interactive fitting can be regarded as a comfort driven approach that complements the prescriptive procedure.

E-mail: m.boymans@amc.nl