DOWNLINK TONE DETECTION AND ADAPTION OF A SECONDARY PATH RESPONSE MODEL IN AN ADAPTIVE NOISE CANCELING SYSTEM

摘要

Adaptive noise cancellation (ANC) circuitry adaptively generates a noise suppression signal from a reference microphone signal that is inserted into a speaker or other transducer output to cause the removal of ambient audio sounds. The error microphone is closest to the speaker that provides the error signal. The secondary path estimation adaptive filter estimates the electro-acoustic path from the noise cancellation circuit via the transducer so that the source audio can be removed from the error signal. Tones in the source audio, such as remote ring tones, are present in the downlink audio during the initiation of the telephone call, and are detected by the tone detector using accumulated tone duration and non-silence hangover counting, 2 Adaptation of the difference path estimation adaptive filter is stopped to prevent adaptation to the tones. The adaptation of the adaptive filters is then sequenced so that any interruption of the secondary path adaptive filter response is removed before allowing the noise-proof generating filter to adapt.