A comparison between coupler gain and insertion gain of hearing aids as used in partially hearing units in five...

A group of 30 school-children attending partially hearing units at ordinary schools had their hearing aids assessed with reference to coupler gain and insertion gain. The results showed no statistically significant difference between the coupler and insertion gain at 250, 500 and 1000 Hz, but a small statistically significant difference with insertion gain greater at 2000, 4000 and 5000 Hz. A large individual variation in results is noted, which would suggest that a standard 2 cm3 coupler is of little use in predicting the output of an aid in a specific child's ear. The presence of wax in the ear canals seems to affect the insertion gain in a positive fashion but this is not statistically significant and further investigation is warranted.