Abstract: An electro acoustic system built-in test and calibration method utilizes a built-in self-test module to send a test signal through a first circuit device to an audio transmitter, causing the audio transmitter to output a test signal, for enabling the test signal to be received by a audio receiver and then processed by a connected circuit device and converted into a feedback digital signal to the self-test module for comparing the linearity relative to the originally provided test signal so that the parameter values and conformity of circuit devices can be optimized subject to comparison result. The test and adjustment procedure is recycled for other parameter items, and a warning signal is produced when proper adjustment cannot be done.

Abstract: An electro acoustic system built-in test and calibration method utilizes a built-in self-test module to send a test signal through a first circuit device to an audio transmitter, causing the audio transmitter to output a test signal, for enabling the test signal to be received by a audio receiver and then processed by a connected circuit device and converted into a feedback digital signal to the self-test module for comparing the linearity relative to the originally provided test signal so that the parameter values and conformity of circuit devices can be optimized subject to comparison result. The test and adjustment procedure is recycled for other parameter items, and a warning signal is produced when proper adjustment cannot be done.

Abstract: An audio device with active noise cancellation (ANC) for coupling to a stereo headset is provided. The audio device comprises an audio processor and an analog ANC control module. The audio processor processes audio data for playback. It optionally can also comprise digital ANC function for tracking and canceling narrow band noise. The analog ANC control module actively cancels wide band noise in the stereo headset based on an audio feedback signal. The audio device further comprises a power amplifier and a feedback processor. The power amplifier is coupled to the output of the audio processor and the analog ANC control module. The power amplifier amplifies the output from the audio processor and the analog ANC control module and sends the amplified signal to the stereo headset. The feedback processor receives the noise from the stereo headset and generates an signal to the analog ANC control module.

Abstract: A dual microphone communication device comprising a first microphone module, a second microphone module and a mixer circuit is provided. The first microphone module amplifies a near-end audio signal to produce a first audio signal. The second microphone module receives and amplifies the near-end audio signal by a fixed gain and a constant phase difference to produce a second audio signal. The mixer circuit subtracts the second audio signal from the first audio signal to produce a third audio signal so that interference resulting from echoes is significantly reduced while keeping, or enhance the near end voice level.