ON MAXIMUM ACHIEVABLE NOISE REDUCTION IN ANC SYSTEMS

Active noise control (ANC) is primarily a signal estimation problem. The nature of noise to be canceled, the acoustic paths, and the transfer functions of microphones/loudspeakers place fundamental limits on the performance of ANC systems. In this paper we analyze the performance of ANC systems from the maximum achievable noise attenuation level (NAL(max)) prospective for different ANC system structures i.e feed-forward, feedback and hybrid. We first derive NALmax for stochastic noise and then generalize the result to accommodate tonal (sinusoidal) noises. These results are invaluable in choosing an ANC design scheme.