1985

Until this time, hearing aids had amplified all types of noise equally. Although they allowed wearers to hear, loud background noise made understanding difficult, and "hearing" did not necessarily mean "comprehending."

The first solution for suppressing noise was the new ASP (automatic signal processing) hearing aids with a two-channel amplifier. These instruments process noise and speech frequencies separately.

When disruptive noise occurs, amplification in the low frequency range is automatically reduced while the high frequency range remains the same. As a result, speech intelligibility is less compromised by ambient noise. When the disruptive noise stops, the hearing aid resumes transmission of broadband frequencies.