Traditional active noise cancellation (ANC) theories and system can’t be directly applied to cancel the noise when the useful signal and noise coexist in the sound field. Consequently, a new system with preprocessed reference input was proposed to solve this problem. Independent component analysis (ICA) in frequency domain was used to preprocess the reference input of ANC system with adaptive algorithm. With the method proposed, the correlation between signal and reference input is decreased. Hence, the int...