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 treated and controlled separately. The basic acoustic equations governing volume velocity control are presented and it is shown that, at low frequencies, this method achieves global sound power reductions in the far-field. Further analysis shows that this method will achieve significant sound power reductions (10 dB or more) for values ofkLof 3·0 or less, whereLis the characteristic dimension of each control segment. Tests conducted in a transmission loss chamber verify the efficacy of volume velocity control using a digital controller. The controller, based on the filtered-X control algorithm, allows for control over a frequency band and results show sound power reductions of 9 dB over a 60 Hz bandwidth. These tests are among the first attempts to use the volume velocity control method over a band of frequencies. The experimental results are complemented by numerical simulations. The results show promise that this methodology is an effective way to control broad band, low-frequency sound transmitted to enclosed spaces, such as airplane or helicopter cabins.