Hybrid SONIC: joint feedforward–feedback narrowband interference canceler

Abstract

SONIC (self-optimizing narrowband interference canceler) is an acronym of a recently proposed active noise control algorithm with interesting adaptivity and robustness properties. SONIC is a purely feedback controller, capable of rejecting nonstationary sinusoidal disturbances (with time-varying amplitude and/or frequency) in the presence of plant (secondary path) uncertainty. We show that although SONIC can work reliably without access to a reference signal, even when the frequency of the disturbance is unknown and possibly time varying, the algorithm can take advantage of such additional source information. Unlike classical hybrid solutions, the reference signal is used only to extract information about the instantaneous frequency of the disturbance. The advance-time advantage, available because the acoustic delay in the system is larger than the electrical delay, allows one to incorporate in the control loop a smoothed, and hence more accurate, frequency estimate. This increases the attenuation efficiency of SONIC and widens its operating range-the modified algorithm can be safely used in the presence of rapid frequency changes. Copyright HYBRID SONIC: FEEDFORWARD-FEEDBACK INTERFERENCE CANCELER 1051 SONIC [5,6] can be summarized as follows:and c > 0 denotes a small constant. The multifrequency version of SONIC was presented in [14]. RemarkFrequency update recursion (6) differs from that proposed in [6]:7) ‡ Note that the signal d 0 .t/ has time-varying amplitude even though the amplitude of s.t/ is constant. This is a typical effect observed when the filtered narrowband signal is nonstationary.