Microperforated panel absorber design: A tutorial

A microperforated panel absorber is best thought of as a noise control system consisting of both the panel itself and the air space behind the panel. This work looks at practical design aspects related to both the panel and the air space. The work by Maa for determining the transfer impedance of the panel is relied on heavily, and it is shown that his equations are useful for characterizing microperforated panels consisting of slit type perforations and for non-uniform hole diameters. Because panels are often placed in dirty environments, the effect of contamination is discussed and it is noteworthy that performance of a panel can sometimes be improved when polluted. The second part of this paper will focus on the design of backings behind the panel. It has been shown that both partitioning and varying the backing cavity depth can greatly improve microperforated panel performance. A number of schemes that Wirt suggested over 30 years ago are used to enhance both the low and broadband frequency sound absorption.