Scientific Article

Characterization of acoustic materials at arbitrary incidence angle using sound field synthesis

¹ Laboratoire d’Acoustique de l’Université du Mans (LAUM), UMR 6613, Institut d’Acoustique – Graduate School (IA-GS), CNRS, Le Mans Université, 72085 Le Mans Cedex 9, France
² Centre de Transfert de Technologie du Mans (CTTM), 20 Rue de Thalès de Milet, 72000 Le Mans Cedex 09, France
³ Centre de Recherche Acoustique – Signal – Humain (CRASH), Université de Sherbrooke, 2500 Bd de l’Université, Sherbrooke, QC J1K 2R1, Canada

^* Corresponding author: Manuel.Melon@univ-lemans.fr

Received: 5 August 2022
Accepted: 15 November 2022

Abstract

Standardized methods for measuring sound absorption such as the impedance tube and reverberation chamber methods are limited to normal or diffuse incidence, respectively. Two research axes have been generally followed in the literature to develop alternative techniques, the first one focusing on the measurement part, that is from the two-microphone technique to the use of microphone arrays or pressure-velocity sensors. The second axis focuses on the excitation part with for instance the use of sound field synthesis techniques. Since acoustic impedance and sound absorption coefficient of materials are classically defined under normal and oblique plane wave excitation, synthesizing an “ideal” plane wave using a loudspeaker array would allow measuring these acoustics quantities using a simple microphone pair. In this article, the effect of the different parameters of a loudspeaker array on acoustic plane waves reproduction on a material’s surface is first numerically studied. Then, numerical and experimental results for the estimation of both impedance and absorption coefficients are reported. These results show that sound field synthesis allows to characterize a material for arbitrary incidence angles over a wide frequency range, thus offering an alternative method to standard techniques and an improvement over existing works.