Active cancellation of acoustic noise using a self-tuned filter

In an increasingly noisy society, methods of reducing noise are becoming more important. This work proposes an analog electroacoustic circuit for active control of narrow-band low-frequency acoustic noise using adaptive filtering techniques. The circuit aims at producing antinoise, which is acoustically added to the disturbing noise to produce an error signal that is fed back to the circuit. The proposed circuit is a modified Kerwin-Huelsman-Newcomb biquad filter that tunes itself to the incoming noise frequency using the zero tuning techniques. The circuit was implemented on a printed circuit board and it was successful in reducing noise by 15-20 dB in open space. Active noise control specifically for narrow-band noise cancellation using adaptive analog filters seems to be a better solution than its digital signal processing counterpart in speed, cost, and robustness.

I. Introduction

Noise has always been a health hazard and nuisance. There are two methods for canceling noise, namely, passive control and active control. Passive control of noise uses techniques like barriers, enclosures, and silencers to attenuate noise [1]. Though the passive silencers work over a broad range of frequencies, they are bulky, costly, and not effective for low frequencies. In active control, the method of antinoise is used [1]. This contains an electroacoustic device that produces antinoise, which has amplitude equal but phase opposite to that of the disturbing noise. The antinoise and the disturbing noise are acoustically added resulting in canceling of both noises. Active noise control (ANC) can result in a large amount of noise reduction when it is of low frequency. At low frequencies, when only plane wave propagation is allowed, ANC offers a great advantage over passive technique [2].