Adaptive compressive gain and level dependent spectral shaping circuitry for a hearing aid include a microphone to produce an input signal and a plurality of channels connected to a common circuit output. Each channel has a preset frequency response. Each channel includes a filter with a preset...http://www.google.com/patents/US5724433?utm_source=gb-gplus-sharePatent US5724433 - Adaptive gain and filtering circuit for a sound reproduction system
