algorithm will not be degraded by the additional audio component picked up by the error microphone, and the ANC system will not cancel the desired audio component, because the audio component is not fed back to the FXLMS algorithm. The additional benefit of using the audio-integrated algorithm is that the adaptive filter St (z) performs the online modeling of the secondary path using the audio signal as an excitation signal. Furthermore, the audio-integrated ANC system saves on overall system cost by using the same analog components- loudspeakers and amplifiers to play the intended audio signal. Noise Signal Noise Source Reference Microphone Antinoise Signal Residual Signal = + Error Microphone Acoustic Domain Secondary Loudspeaker Analog Domain Preamplifier Power Amplifier Preamplifier Anti-Aliasing Filter Reconstruction Filter Anti-Aliasing Filter ADC DAC ADC FeedbaCk audio-integrated anC SyStemS y (n ) x (n ) Digital Domain W (z ) ^ S (z ) The concept of a single-channel feedback ANC system is illustrated in Figure 3 for the duct noise problem. The FXLMS algorithm, the secondary path S (z), and its estimation St (z) are the same as in the feedforward ANC system. e (n ) LMS Figure 1. A block diagram of the feedforward ANC system. Headphone Cup 1 3 Power Amplifier Preamplifier Preamplifier Reconstruction Anti-Aliasing Filter Filter Anti-Aliasing Filter ADC DAC ADC u (n ) x (n ) ^ S (z ) 2 W (z ) Copy y (n ) + ∑ + a (n ) Audio Source a ′(n ) ^ S (z ) - e (n ) + ∑ LMS LMS Figure 2. A block diagram of the audio-integrated feedforward ANC system. 36 IEEE Consumer Electronics Magazine ^ OCTOBER 2016 e ′(n ) Note: 1: Secondary Loudspeaker 2: Error Microphone 3: Reference Microphone Red Signal: Unwanted Noise Blue Signal: Antinoise Green Signal: Residual Noise Yellow Signal: Audio/Music