Patent ID: 8005246

Claim:
A hearing aid comprising: (a) input transducer means for converting input acoustic signals into electrical input signals; (b) signal processor means operable: (i) to divide said electrical input signals into a plurality of frequency bands signals; (ii) to perform an intermodulation distortion generation operation on each of said frequency band signals, said intermodulation distortion generation operation comprising 1. providing an all pass filter means for generating two signals from each frequency band signal, a first all pass signal h 1 (t) and a second all pass signal h 2 (t), the second all pass signal having a phase offset of 90 degrees from the first all pass signal; 2. forming an instantaneous amplitude A(t) from said first all pass signal h 1 (t) and a second all pass signal h 2 (t), wherein A(t) comprises the absolute value of h 1 (t) and h 2 (t); and 3. modulating either said each frequency band signal or the first all pass signal h 1 (t) according to said instantaneous amplitude signal A(t) to produce a modulated band signal for each of said frequency band signals; and (c) output transducer means operable to produce and output acoustic signal corresponding to a combination of said modulated band signals.