title: Enhancing the absorption properties of acoustic porous plates by periodically embedding Helmholtz resonators.
abstract: This paper studies the acoustical properties of hard-backed porous layers with periodically embedded air filled Helmholtz resonators. It is demonstrated that some enhancements in the acoustic absorption coefficient can be achieved in the viscous and inertial regimes at wavelengths much larger than the layer thickness. This enhancement is attributed to the excitation of two specific modes: Helmholtz resonance in the viscous regime and a trapped mode in the inertial regime. The enhancement in the absorption that is attributed to the Helmholtz resonance can be further improved when a small amount of porous material is removed from the resonator necks. In this way the frequency range in which these porous materials exhibit high values of the absorption coefficient can be extended by using Helmholtz resonators with a range of carefully tuned neck lengths.
authors.affiliation: Laboratoire d'Acoustique de l'Université du Maine, L'Université Nantes Angers Le Mans, Université du Maine, CNRS, UMR-6613 CNRS, Avenue Olivier Messiaen, 72085 Le Mans, France.
authors.forename: J-P
authors.initials: JP
authors.lastname: Groby
authors.affiliation: Laboratoire d'Acoustique de l'Université du Maine, L'Université Nantes Angers Le Mans, Université du Maine, CNRS, UMR-6613 CNRS, Avenue Olivier Messiaen, 72085 Le Mans, France.
authors.forename: C
authors.initials: C
authors.lastname: Lagarrigue
authors.affiliation: Laboratoire d'Acoustique de l'Université du Maine, L'Université Nantes Angers Le Mans, Université du Maine, CNRS, UMR-6613 CNRS, Avenue Olivier Messiaen, 72085 Le Mans, France.
authors.forename: B
authors.initials: B
authors.lastname: Brouard
authors.affiliation: Laboratoire d'Acoustique de l'Université du Maine, L'Université Nantes Angers Le Mans, Université du Maine, CNRS, UMR-6613 CNRS, Avenue Olivier Messiaen, 72085 Le Mans, France.
authors.forename: O
authors.initials: O
authors.lastname: Dazel
authors.affiliation: Laboratoire d'Acoustique de l'Université du Maine, L'Université Nantes Angers Le Mans, Université du Maine, CNRS, UMR-6613 CNRS, Avenue Olivier Messiaen, 72085 Le Mans, France.
authors.forename: V
authors.initials: V
authors.lastname: Tournat
authors.affiliation: Laboratoire d'Ingénierie des Systèmes Mécaniques et des Matériaux, EA 2336, Supméca, 3 Rue Fernand Hainaut, 93407 Saint-Ouen Cedex, France.
authors.forename: B
authors.initials: B
authors.lastname: Nennig