STUDY OF ANECHOIC WEDGES FOR IMPROVED LOW-FREQUENCY SOUND ABSORPTION

Abstract

Anechoic chamber are rooms / enclosures that designed to create acoustic free-field conditions for many standard acoustic and sound measurements, such as, sound source localization tests, machinery noise rating, etc. To achieve this free-field condition, the anechoic chambers have their walls, roofs and ceiling covered with materials that can absorb sounds completely with negligible reflection. One of the most widely used technology for this anechoic chamber is to cover all reflecting surfaces with anechoic wedges. This research project is aimed at designing anechoic wedges for high sound attenuation in a broad range of low to mid frequencies. Therefore, a parametric study was done using FEM simulations in COMSOL to understand the effect of various geometrical features of the anechoic wedges in an anechoic chamber on the sound absorption performance of the chamber. Impedance tube method was used for finding the Sound Absorption Coefficient of various configurations of the anechoic wedges. Common findings of this research are:  Harvard Linear Structure of wedges gives the best sound absorption coefficient in a broad range of low frequencies (<500 Hz).  Perpendicular arrangement of wedges has higher sound absorption coefficient than parallel arrangement.  Reducing wedge gap increases sound absorption coefficient. The learning from this study paves the way for design of optimum anechoic wedges within the dimensional constraints.