Effect of high pass filtering of the regenerated reference signal in a single channel active noise control system

Abstract

An acoustic noise cancellation (ANC) system with regenerative feedback synthesizes its own reference signal based on the error signal and the adaptive filter output. The prime objective of such a configuration is to estimate the primary noise and use it as a reference signal to the control filter without the need for an additional reference sensor. This paper presents the results of and discusses the use of a high pass filter in the regenerated branch of the reference signal for a single channel active noise control system. With the high pass filter, it is seen that the speed of convergence is better. The high pass filter blocks any dc component of the signal that gets introduced in the system and stabilizes the control system. It is also noticed that for a small value of the step size, the effect is much more pronounced. With the high pass filter, the regenerative feedback system performs as well as a traditional feedforward active noise control system. It is expected that in systems where variable step size is required, the presence of the high pass filter, will be beneficial and more needed.