Guidelines for fitting multiple memory hearing aids.

Fitting guidelines to determine candidacy for multiple memory hearing aids and the choice of amplification for each memory are devised by reviewing studies on the selection of amplification for different listening conditions. The guideline for determining candidacy comprises three factors: (1) difficulty hearing in acoustically diverse conditions, (2) an average high-frequency hearing loss greater than about 55 dB HL, and (3) ability to vary the low-frequency gain by at least 5 dB. People who meet all three criteria are highly likely to benefit from multiple memories. People who meet criteria 1 and 2 or 1 and 3 are possible candidates. The guideline for determining the amplification characteristics needed for each memory also enables the fitter to determine the number of memories needed. The following recommendations for amplification characteristic for various listening conditions are based on the literature review: linear amplification with the prescribed National Acoustic Laboratories' (NAL) frequency response is recommended for listening to speech in quiet; substantial high-frequency compression is recommended for ease of understanding two voices that differed by 10 dB in overall level; a linear response steeper than the NAL response is recommended for ease of understanding speech in a low-frequency background noise; low-frequency compression is recommended to reduce annoyance of low-frequency background noise; and a linear response flatter than the NAL response is recommended for listening in high-frequency background noise, and possibly for listening to music.