Earmoulds: some benefits from horn fitting

The narrow bore of conventional hearing aid earmoulds restricts the transmission of higher auditory frequencies. For subjects with moderate to severe high-frequency hearing loss this is likely to have an adverse effect on the perception and recognition of phonemes with high-frequency components. Twenty-two subjects with predominantly high-frequency hearing loss underwent a series of tests to compare the performance of earmoulds having conventional 1.9 mm through-tubing with earmoulds fitted with a smooth horn with a final internal diameter of 4 mm. The test battery comprised free-field Békésy audiometry, in-the-ear pressure measurement, speech audiometry using AB word lists and semantic differential rating of the relative sound quality of the two systems. Subjectively the horn fitting was rated as clearer, more natural, undistorted and acoustically comfortable. Objectively, by both Békésy audiometry and in-the-ear pressure measurement, the horn gave more gain in the higher auditory frequencies. With the horn there was improved recognition of phonemes, especially fricatives and affricatives.