Numerical analyses of the sound absorption of cylindrical microperforated panel space absorbers with cores

Abstract

Microperforated panels (MPPs) are next-generation absorption materials because they can provide wideband sound absorption without fibrous materials and can be composed of diverse materials to meet global environmental demands. The fundamental absorbing mechanism is Helmholtz-resonance absorption due to perforations and an air cavity. MPPs are typically backed by rigid flat walls, but to reduce the restrictions on the MPP absorber properties, one of the authors has proposed MPP space sound absorbers without backing structures, including three-dimensional cylindrical microperforated panel space absorbers (CMSAs). Advantages of MPPs without backing structures are design flexibility and ease of use. Besides, the absorption characteristics of a CMSA with a core, which has a rigid cylindrical core inside the CMSA, have been experimentally tested, but a method to predict the absorption characteristics is necessary to design CMSAs with cores. Herein the two-dimensional combined Helmholtz integral formulation method is employed, and its prediction accuracy is evaluated by comparing the measured and predicted absorption characteristics of a CMSA with a core. Furthermore, a parametric study with regard to the core size is carried out to investigate the transition of the absorbing mechanism.

Diffuse-field sound absorption characteristics of a spherical-microperforated space absorber

“…In our previous studies [6][7][8][9], three-dimensional MPP space absorbers (3D-MPAs) were proposed as an alternative use of conventional MPPs. A 3D-MPA is a three-dimensional object made with an MPP in shapes such as cylinder, rectangular, etc.…”

“…By using MPPs in this way, it is possible to add necessary sound absorption to a room without changing its interior design, also enables one to use them as a kind of sound absorbing furniture with attractive design. So far, a cylindrical MPP space absorber (CMSA) [6] and a rectangular MPP space absorber (RMSA) [7], and their variants, e.g., with core and porous filling [8,9], were experimentally and theoretically studied.…”

Acoustic Metamaterials: A Potential for Cabin Noise Control in Automobiles and Armored Vehicles

“…Again, cabin space is affected. The inevitability of a backing air cavity could, however, be potentially minimized or omitted based on the recent work by Toyoda et al [2015] albeit extensive further studies are necessary for such realization in panels. From these works, MPP seems to be an improved concept of HR albeit the minute orifices may likely trap dust particles.…”