A DOUBLE-BLIND CROSS-OVER STUDY OF A NONLINEAR HEARING-AID

New hearing aids are usually introduced after clinical trials. These a re mostly based on subjects' reports, in which it is possible that the subject's judgment of the acoustic performance might be influenced by the awareness that it is a new hearing aid which is being investigate d. To examine the benefit of a new non-linear amplification circuit, a double-blind cross-over study was conducted. Two 'new' hearing aids w ere developed; they were identical in external appearance and differed only in that one involved ordinary linear amplification while the oth er employed compressive amplification (the K-amp circuit). Forty-five experienced users with sensorineural hearing loss, aged 60-80 years, u sed each of the aids for ten weeks, in balanced order. The subjects' n eed for hearing aid ranged from listening to radio and television to e xtensive use in all kinds of demanding listening situations. The resul ts, using a structured questionnaire concerning real-life settings, sp eech reception tests and subject preferences for a particular hearing aid, showed little difference between the two hearing aids. Twenty-thr ee subjects selected the non-linear amplification circuit, 20 subjects preferred the linear hearing aid and two chose to return to their pre vious aid. No consistent differences between those preferring the line ar circuit and those preferring compression were found. It can be conc luded that this compression amplification circuit is not significantly preferred to the traditional linear hearing aid.