AN INTRODUCTION TO THE CONTROL OF SOUND FIELDS BY OPTIMISING IMPEDANCE LOCATIONS ON THE WALL OF AN ACOUSTIC CAVITY

Abstract

The paper presents a possible means of solving the problem of optimizing impedance locations on the walls of an acoustic cavity with rigid walls, when the goal is to reduce the sound level generated by a velocity source inside the cavity. First, an elementary analytical study of an academic situation shows how to deal with the problem. The methodology is then used on a finite element model of the cavity. Severe conditions constitute the framework because the situation is that of a large room (approx. 80 m3) with a low frequency anti-resonance (arbitrarily around 70 Hz), with a limited number of pieces of absorptive material on the walls, called here impedances or impedance patches, and finally because the study begins with the search for optimal locations along a line on a face of the cavity. Under these conditions and until now, an attenuation of only a few dB has been obtained when the sound level minimization occurs at a small number of points, called here microphones, and less than one dB on a large number of microphones. Upon taking into consideration the narrow framework, these results encourage more extensive investigations.