Abstract
As a trial to improve the performance of passive noise barriers by applying the active control technique, basic theoretical and experimental investigation has been made. At first, the basic conception of the “active noise barrier” is presented, in which an active control system composed of a noise detector, an error sensor, a secondary sound source and an adaptive signal processing unit is attached to a passive barrier. As a preliminary study, a simple numerical calculation was performed according to the Fresnel-Kirchhoff diffraction theory, and the adaptability of the active control has been basically confirmed. Next, 1/2 scale model experiments were performed in a hemi-anechoic room to inve stigatethe effectiveness of the active noise barrier. In this experimental study, the method combining the “filtered x LMS” algorithm and the “block processing technique” was applied as the adaptive signal processing technique. As a result, it has been found that the active noise barrier is effective for sound attenuation in low frequencies.
