Benefit provided by improved high frequency audibility: Possible involvement of acclimatisation and aetiology

At least one essential problem remains when hearing impaired patients are treated with amplifiers. People who have lost hearing sensitivity over several years have usually got accustomed to reduced peripheral activity at high frequencies. They have forgotten how to interpret high frequency input, so when they are fitted with a hearing instrument, there is a significant risk that the perceived benefit is limited. The new hearing aid user may simply not be capable of taking advantage of the newly re-audible sounds. The problem is that other factors than audibility govern perception. The precondition for audibility is obvious, but it is not a sufficient condition for speech perception. In a number of recent studies on the benefit provided by improved high frequency audibility upper frequency limits for the improvement of word recognition were found, and the authors concluded that audibility does not automatically provide intelligibility. One of the main objections that may be made towards this conclusion involves the potential need for acclimatisation to the re-audible sounds that may well be caused by central reorganisation. How to quantify such supra-threshold hearing deficit is one of the subjects for this project. Another one is to investigate the course of acclimatisation to peripheral amplification in subjects with high frequency hearing losses. The results of the project should increase our understanding of the underlying mechanisms of getting used to new auditory information.