Best practice for positioning sound absorbers at room surface

Abstract

A method to facilitate the efficient positioning of sound absorbing materials on the walls of an enclosure is proposed by quantifying the contribution of each wall segment to the sound field in a vibro-acoustic transfer matrix. Wall reflections can be considered as secondary sources of radiation, whose strengths depend on the primary source and the amount of absorption by the walls. Based on this idea, the proposed evaluation method to quantify the degree of effectiveness for each wall segment is to quantify the linear independence of the rows or columns in a transfer matrix. The multiplication of quantified linear independence of elements in two transfer matrices consisting of the transfer path of sound is suggested as an observation parameter for selection. The proposed method is verified through numerical simulations and experiments. As absorbing patterns are treated at the surfaces with the highest linear independence in the transfer matrix, the sound pressure at most frequencies decreases for a point receiver or a finite region of receivers. The proposed method has advantages in terms of required effort, because it does not require any iteration process. The proposed method can produce a practically applicable solution without any detailed assumptions about the sound source and boundary conditions which are not clearly known at the design stage.