[Clinical comparison of a digital with an analog hearing aid]

The benefit of innovative hearing aid technology can be evaluated in clinical trials. The present study describes the comparison of a new digital hearing aid with an analogue device serving as a reference. The tests were carried out with 15 experienced hearing aid wearers. To prevent the influence of different fitting algorithms such as prescriptive or loudness-based the digital devices were not renewed fitted but their level- and frequency-depending gain was adjusted to that of the reference. Different tests concerning loudness perception (category loudness scaling) speech discrimination in noise (the Göttingen sentence test) and self-assessment of the benefit by questionnaires were performed. All tests yielded slightly better results for the digital hearing aid. The speech audiometric evaluation showed somewhat better discrimination for the test-device. The questionnaires yielded a marked preference for the digital device. Because the study was not blinded influences due to the knowledge of the subjects of testing a new technology generally can occur. On the other hand, the question arises whether present audiometric tests sufficiently consider signal processing of modern hearing systems. Furthermore, one has to take into account that only a few of the features of digital technology such as noise-reduction and feedback-cancellation were considered in this study to allow for a sensible comparison. Because of the large number of possibilities offered by digital technology additional benefit by the hearing aid can be expected.