On the use of the local reflection coefficient to assess the diffuse field sound absorption coefficient of a porous material

Auteurs

Franck Sgard, Direction de la Recherche, Institut de Recherche Robert-Sauvé en Santé et Sécurité du Travail (IRSST), Montréal, H3A 3C2, QC, Canada
Noureddine Atalla, Centre for Research in Acoustics-Signal-Human, Department of Mechanical Engineering, Université de Sherbrooke, Sherbrooke, J1K 2R1, QC, Canada
Olivier Robin, Centre for Research in Acoustics-Signal-Human, Department of Mechanical Engineering, Université de Sherbrooke, Sherbrooke, J1K 2R1, QC, Canada

Type de document

Études primaires

Année de publication

2024

Langue

Anglais

Titre de la revue

Frontiers in acoustics

Résumé

The diffuse field sound absorption coefficient (SAC) of a sound absorber can be obtained from an average over the incidence angles of the oblique incidence plane wave SAC. The plane wave SAC can be derived from the plane wave complex-valued reflection coefficient defined as the ratio of the reflected sound pressure at a given point on the material surface to the incident sound pressure at the same point. In practice, the material is excited by a monopole, and the reflection coefficient becomes a local quantity which is a function of the source height and the radial distance from the source. This local reflection coefficient obtained at various points on the material surface is commonly used to approximate the oblique incidence plane wave reflection coefficient. The error in estimating the diffuse field SAC introduced by this approximation has not been explored in the literature. This paper investigates this error as a function of the material extent, thickness, and source height using an analytical approach to calculate the local reflection coefficient. The calculation is based on Allard’s model which describes the sound propagation above an infinite lateral extent porous material backed by a rigid wall and excited by a monopole. Using finite element simulations as a reference, the analytical model is shown to provide a good approximation of the diffuse field sound absorption performance of sufficiently large material areas. The diffuse field SAC calculated from plane wave reflection coefficients and local reflection coefficient are compared. The limitations inherent in deriving diffuse field SACs from local reflection measurements obtained with a monopole are highlighted.

Mots-clés

Absorption acoustique, Sound absorption, Lutte contre le bruit, Noise control, Conductibilité des matériaux, Conductivity of materials, Niveau de bruit, Noise level, Dispositif acoustique, Acoustic device, Matière poreuse, Porous material, Bruit basse fréquence, Low-frequency noise, Vibration basse fréquence, Low frequency vibration, Transmission du son, Sound transmission, Modèle, Model, Mathématique, Mathematics

Numéro de projet IRSST

2018-0027

Citation recommandée

Sgard, F., Atalla, N. et Robin, D. (2024). On the use of the local reflection coefficient to assess the diffuse field sound absorption coefficient of a porous material. Frontiers in Acoustics, 2. https://doi.org/10.3389/facou.2024.1414356