A noise-cancelling system includes headset for generating a feedback signal for noise-cancellation in response to sound externally generated from the headset. An encoded microphone signal is generated in response to the first feedback signal. An audio generator can be used to generate a noise-cancellation signal in response to the encoded microphone signal and to generate an electronic audio signal in response to the encoded microphone signal and a first output audio signal. An audio connector is provided to couple the encoded microphone signal from the headset to the audio generator and to couple the first electronic audio signal to the headset.

An audio channel control circuit includes a filter module and a determining module. The audio channel control circuit receives a first audio signal and a second audio signal from an audio device. The first audio signal loads a first carrier signal, while the second audio signal loads a second carrier signal. The first carrier signal and the second carrier signal have different phases. The filter module filters the first audio signal and the second audio signal, separating the first carrier signal from the first audio signal and the second carrier signal from the second audio signal. According to the phases of the first carrier signal and the second carrier signal, the determining module chooses a speaker of the left audio channel or a speaker of the right audio channel to output the first audio signal or the second audio signal.