A COMPARISON OF USING SOUND PRESSURE AND PARTICLE VELOCITY AS ERROR SIGNALS FOR LOCAL ACTIVE NOISE CONTROL

摘要

Controlling the sound pressure as the error signal is well understood for local active noise control, and controlling both the sound pressure and the sound particle velocity has been proposed to improve the performance of the system. However, the performance of controlling only the sound particle velocity is still not clear, which is investigated in this paper. Two local active noise control systems are considered which use either the sound pressure or the sound particle velocity as the error signal. The primary sound field is assumed to be made of plane waves and the secondary source is a monopole. Simulations are carried out to cancel either the squared sound pressure or the squared sound particle velocity in one direction at the error location. The noise reduction at error microphones and the surrounding spatial distributions indicates that using the sound pressure as the error signal always achieves the best sound pressure control at the error sensor, while controlling the sound particle velocity is not favourable in the near field or at the low frequency in terms of sound pressure reduction. Controlling the sound particle velocity may provide larger quiet zone in the far field or at the high frequency. The control performance is also affected by the propagation direction of the primary sound field and the secondary sound field at the error location, and this angle should be less than 90 degrees to avoid noise amplification with control.