Hybrid passive–active absorption using microperforated panels

Abstract

A theoretical and experimental study of a proposed hybrid passive–active plane-wave system to provide broadband acoustic absorption is presented. The passive absorber consists of a microperforated panel (MPP), used in place of conventional fibrous materials, in front of an air layer. The active system uses an active transducer (a loudspeaker), an error sensor (a microphone), and an adaptive controller. MPPs are thinner than fibrous materials and provide a better solution in hygienic environments. For two such systems, the dependence of performance on MPP parameters is studied for two control strategies: impedance matching and pressure release. The first condition is found to be better for cases where the acoustic impedance of the system approaches that of air. Otherwise, the pressure-release condition is better, and a wideband solution is the implementation of the active control system up to a frequency where the natural band of the passive system provides higher absorption. Therefore, the use of a low-pass filter in the error signal is implemented to afford hybrid passive–active wideband absorption. The control effort of active system is also considered. Experimental verification shows good agreement with theory, and an average absorption coefficient of 0.82 in the frequency bandwidth 100 to 1600 Hz was achieved.

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

“…Compared to the impedance-matching condition, there is no cavity absorption. That means the absorption performance is sensitive to the properties of the MPP [9]. Thus, the parameters of the MPP should be carefully selected when applying the pressure release condition, otherwise the system would yield low sound absorption.…”

“…The panel vibration effect is considered here, unlike the previous works [8][9][10]. A theoretical model is presented for predicting the impedance of the flexible MPP.…”

“…control conditions theoretically and experimentally, and proposed a thinner hybrid system using MPPs instead of typical sound absorption materials [9]. However the MPP were thought to have no flexible effect in the system.…”

An Experimental Study of a Multi-Size Microperforated Panel Absorber

“…So far, however, most of these efforts resulted in thicker sound absorbers because the panels were arranged in series or because porous absorbers were placed behind the panel [5][6][7][8][9][10][11]. Another idea was to employ active control using a loudspeaker or thin actuator as a secondary source in place of the rigid back wall [12,13]. However, the methods proposed by Cobo et al [12] and Cuesta et al [13] seem to be impractical in real applications.…”

“…Another idea was to employ active control using a loudspeaker or thin actuator as a secondary source in place of the rigid back wall [12,13]. However, the methods proposed by Cobo et al [12] and Cuesta et al [13] seem to be impractical in real applications.…”