Claus Nielsen

Research Audiologist

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Hearing-aid fitting software typically prescribes earmould vent size based on low-frequency hearing loss, in consideration of occlusion problems. This study investigated another potential predictor of optimal vent size: middle-ear compliance.

Clinical study

82 regular clients at a hearing-aid shop in Italy took part in the study and provided data for 119 ears in total. For each ear, middle-ear compliance was determined by tympanometry, and earmould vent size was systematically varied until the size was found that just solved the client’s occlusion-related problems with own voice. Hearing threshold levels were also measured.

Observed relations

The statistical analysis showed that 59% of the variation in vent size could be explained by the measured compliance values, whereas low-frequency hearing loss explained as little as 0.3%. That is, we found no relation between low-frequency hearing loss and the required vent size. This is in contrast to the common wisdom that vent size should be prescribed from the amount of hearing loss at the low frequencies.

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Further reading

Carle R, Laugesen S, Nielsen C (2002). Observations on the relations among occlusion effect, compliance, and vent size. Journal of the American Academy of Audiology, 13(1), p. 25-37.

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    Study Partners

    This study was performed in collaboration with Roberto Carle, Audiovox, Livorno, Italy, who collected the data.