Clinical measurement of hearing aid insertion gain

The probe microphone devised by Lauridsen & Günthersen (1981) was tested in a clinical situation, and the results were compared with those obtained with a miniature electret microphone place in the ear canal (cf. Harford, 1980), and also with those obtained with the eardrum microphone on the acoustic manikin KEMAR. Good agreement was found between all three methods. Investigation of the insertion gain in 82 ears, fitted with hearing aids according to the classical criteria, revealed a reduction in the insertion gain in the higher frequency bands, starting from an average of 2 kHz.