A numerical study of double-leaf microperforated panel absorbers

• Published in: Applied acoustics 2006-07, Vol.67 (7), p.609-619
• Main Authors: Sakagami, Kimihiro, Morimoto, Masayuki, Koike, Wakana
• Format: Article
• Language: English
• Subjects: Acoustics; Applied sciences; Building insulation; Buildings; Buildings. Public works; Computation methods. Tables. Charts; Double-leaf structure; Exact sciences and technology; External envelopes; Fundamental areas of phenomenology (including applications); Microperforated panel; Noise: its effects and control; Physics; Sound absorption; Sound insulation; Structural analysis. Stresses
• ISSN: 0003-682X; 1872-910X
• DOI: 10.1016/j.apacoust.2005.11.001

Microperforated panel (MPP) absorbers are promising as a basis for the next-generation of sound absorbing materials. Typically, they are backed by an air-cavity in front of a rigid wall such as a ceiling or another interior surface of a room. Indeed, to be effective, MPP absorbers require the Helmholtz-type resonance formed with the backing cavity. Towards the creation of an efficient sound-absorbing structure with MPPs alone, the acoustical properties of a structure composed of two parallel MPPs with an air-cavity between them and no rigid backing is studied numerically. In this double-leaf MPP (DLMPP) structure, the rear leaf (i.e., the MPP remote from the incident sound) plays the role of the backing wall in the conventional setting and causes resonance-type absorption. Moreover, since a DLMPP can work efficiently as an absorber for sound incidence from both sides, it can be used efficiently as a space absorber, e.g., as a suspended absorber or as a sound absorbing panel. The sound absorption characteristics of the double-leaf MPP are analysed theoretically for a normally incident plane wave. The effects of various control parameters are discussed through a numerical parametric study. The absorption mechanisms and a possible design principle are discussed also. It is predicted that: (1) that a resonance absorption, similar to that in conventional type MPP absorbers, appears at medium-to-high frequencies and (2) that considerable “additional” absorption can be obtained at low frequencies. This low-frequency absorption is similar to that of a double-leaf permeable membrane and can be an advantage compared with the conventional type of MPP arrangement.