AFA BASED PERIODIC NOISE CANCELLATION

Abstract

There are many methods for active cancellation of low-frequency periodic noise. Now a new efficient method is investigated. By means of a resonator based observer structure all harmonic components (up to the half of the sampling frequency) can be suppressed. Since the resonator filters out the signal at its own frequency, the rate of suppression is theoretically infinite. Since the system needs a reference signal only to estimate the frequency of the noise to be suppressed, it can be any signal, relatively free of noise, with the same frequency as the primary source. One of the advantages of the method is that the reference source can be either the error sensor, or any other microphone. For the successful noise cancellation the system needs information about the acoustic transfer function, at least its values relatively densely. There was applied a transfer function measurement method based on the resonators. The practical results were obtained by means of a DSP 96002 System Board.