With things like the telephone, speech, and even the microwave timer being in the hearing range of about 900 Hz to 3,000 Hz, is it possible to have a hearing aid that actually "filters" the noise to adjust it to his hearing range?
Also, what kind of percentage of hearing loss is there in the 1,500 Hz range? Perhaps if things like the telephone or even the microwave could be changed to a lower frequency, it may be distinguishable?