Clinical trials with a programmable hearing aid set for various listening environments.
A conventional hearing aid has a frequency response that does not change much at normal listening levels. It is therefore unlikely that optimal speech intelligibility and optimal listening comfort can be obtained simultaneously, or in different listening environments. With a programmable hearing aid with multiple memories the listener can choose between a range of sound pictures, which increases the chance of finding a suitable frequency curve for each listening situation. The programmable hearing aid with eight separate settings stored in eight memories, was compared with personal hearing aids fitted according to the recommendations of the National Acoustic Laboratories (NAL) by 22 experienced hearing aid users. One memory of the programmable hearing aid was initially fitted according to the NAL recommendation. The other memories were programmed to give variations around that recommendation. One aim was to investigate whether the hearing-impaired user took advantage of different frequency responses to achieve listening improvements in acoustically different environments. Another aim was to evaluate the ergonomic and acoustical features of the programmable hearing aid, compared with other well fitted hearing aids. The evaluations were based on comparisons of the test hearing aid to the personal aid for each subject, looking at speech tests, direct paired comparison judgements, sound quality judgements and interviews. A majority of the subjects experienced substantial benefit from being able to use different frequency response curves in different environments. With the test hearing aid the subjects performed better in speech discrimination tests in noise.(ABSTRACT TRUNCATED AT 250 WORDS)