Hearing aid prescription rules using insertion gain measurements.

Many of the decisions regarding hearing aid selection and use are based mainly upon clinical impressions. It was therefore decided to investigate whether the old fitting of 25 aided subjects with moderate hearing loss could be improved by using more precise prescription rules and a real ear measuring technique. The rules formulated should give a frequency response of moderate low and pronounced high frequency gain. The application of these rules resulted in improved high frequency gain and better speech discrimination for consonants in noise. As a result of the investigation, the routine procedure of hearing aid fitting has been revised. Earmold modifications of different types should be used more often and real ear canal measurements are recommended for incorporation in the routine examination of hearing aid performance.