Broad Objectives: To derive a prescription formula, more effective than NAL-NL1, for non-linear hearing aids.

To produce the NAL-NL2 prescription formula by improving upon the NAL-NL1 prescription. The specific improvements to be aimed for are:

a)     To be mathematically more robust for the very high frequencies, so that compression ratios appear more reasonable at 4 and 6 kHz;

b)    To use newer data about the effectiveness of amplification in quiet and in noise, particularly for people with severe and profound hearing loss; 

c)     To use newer data concerning acclimatization and the loudness desired by hearing-impaired people;

d)     To produce a useable prescription for all input levels, frequencies, and hearing losses, even when the underlying data suggest that there is no single optimal amount of amplification for particular combinations input level, frequency and hearing loss.