Double-leaf microperforated panel space absorbers: A revised theory and detailed analysis

Abstract

A double-leaf microperforated panel space absorber (DLMPP) is composed of two microperforated panels (MPPs) placed in parallel with an air-cavity in-between, without a back wall or any backing structure. This was proposed as a space sound absorber, which can be used for a sound absorbing screen or partition. A conventional MPP absorber with a rigid back wall is effective only around its resonance frequency, which is usually at middle frequencies, and not effective at low frequencies. However, a DLMPP can be effective also at low frequencies, because an additional sound absorption is produced by its acoustic flow resistance. In the authors' previous work, theoretical analyses on the acoustic properties of a DLMPP were carried out using a simplified electro-acoustical equivalent circuit model. However, the equivalent circuit model includes an approximation, and more sophisticated theory is required for a better prediction and detailed discussion. In this paper, a revised theory for a DLMPP is presented: A Helmholtz integral formulation is employed to obtain a rigorous solution for more precise prediction of the absorptivity of a DLMPP. The result of the present revised theory is compared with that of the equivalent circuit model, and the difference between them is discussed. A parametric survey is made through numerical examples by the present revised theory to discuss its acoustic properties.

Sound absorption of a double-leaf micro-perforated panel with an air-back cavity and a rigid-back wall: Detailed analysis with a Helmholtz–Kirchhoff integral formulation

“…In the present paper, a novel approach to the double MPP absorber by using strict wave theory based on Helmholtz-Kirchhoff integral formulation [15][16][17][18] is proposed. Although ITM and its similar approach can be well used to obtain correct solution for multiple layer absorption structures including double-leaf MPPs, Helmholtz-Kirchhoff integral formulation is more general and expandable, which can be extended to the cases where various other construction (e.g., elastic support, honeycomb in the cavity, etc., that will be dealt with in further studies) are included.…”

Modeling of micro-perforated panels in a complex vibro-acoustic environment using patch transfer function approach

“…The air gap/volume behind the MPP provides an acoustic stiffness, 4 which leads to resonance-type absorption with the perforation. This cavity-backed MPP finds its use in various system configurations and therefore deserves a particular treatment.…”

“…This is done in Fig. 7, in which the impedance of the MPP, @S=W, is compared to that of the cavity Z ii for one particular patch (3,4). It can be seen that, @S=W are generally larger than Z ii , except for frequencies close to the natural frequencies of the cavity.…”

“…Such devices, taking various forms, can loosely be refereed as microperforated structure. Double layer [2][3][4] or multiple layer absorbers 5 using MPPs are typical examples. The insertion of an additional micro-perforated panel increases the acoustic resistance of the absorber and extends the effective absorption band toward a lower frequency.…”

Sound Absorption of Hybrid Passive-Active System Using Finite Flexible Micro-Perforated Panels

“…Thus the total thickness of the absorber can be decreased. There are various types of MPP absorbers designed to improve the absorption performance [12][13][14]. Besides, it is found that sound-induced vibration of MPPs can affect the sound absorption of the systems and many research studies have been carried out on this topic.…”