VOLUME VELOCITY CONTROL OF SOUND-TRANSMISSION THROUGH COMPOSITE PANELS

A design method for minimizing the sound transmitted through an array of panels is presented. This method is based on minimizing the volume velocity of individual segments of the array using integrated control loudspeakers. In this manner, each of the control segments can be trea ted and controlled separately. The basic acoustic equations governing volume velocity control are presented and it is shown that, at low fre quencies, this method achieves global sound power reductions in the fa r-held. Further analysis shows that this method will achieve significa nt sound power reductions (10 dB or more) for values of kL of 3 . 0 or less, where L is the characteristic dimension of each control segment . Tests conducted in a transmission loss chamber verify the efficacy o f volume velocity control using a digital controller. The controller, based on the filtered-X control algorithm, allows for control over a f requency band and results show sound power reductions of 9 dB over a 6 0 Hz bandwidth. These tests are among the first attempts to use the vo lume velocity control method over a band of frequencies. The experimen tal results are complemented by numerical simulations. The results sho w promise that this methodology is an effective way to control broad b and, low-frequency sound transmitted to enclosed spaces, such as airpl ane or helicopter cabins. (C) 1998 Academic Press Limited.