A comparison of open-loop feedforward and closed-loop methods for active noise control using volume velocity minimization

Abstract

This paper focuses on the application of the concept of volume velocity minimization to lower the sound generated by a vibrating surface. The motion of a vibrating surface is measured using an accelerometer, and a speaker is driven so that the net volume velocity of the two is lowered. This concept is tested on a two-speaker system. One speaker acts as the noise source, and the other as the control speaker (noise suppressor). Using this system, the effectiveness of three control strategies are evaluated—open-loop feedforward, closed-loop proportional, and closed-loop optimal control. The feedforward system gives noise reductions of 5–25 dB over the range from 100 to 800 Hz. The closed-loop systems give reductions of 5–30 dB over the range from 175 to 800 Hz. The feedforward system is found to have the best performance below the suppressor’s first resonance, while the closed-loop systems have best performance near the first resonance. Speaker coupling is found to have little effect on system performance.