The sound absorption property of microperforated panel with partitioned cavity

Abstract

In order to broaden the sound absorption bandwidth of single-leaf microperforated panel(MPP),The structure of MPP with partitioned cavity is introduced and its sound absorption performance is studied by impedance tube experiment. Results show that the MPP with partitioned cavity has two sound absorption peaks. Meanwhile, the sound absorption bandwidth is broaden and the sound absorption performance of the low and middle frequency is improved. Introduction With the development of economic construction, urban noise is more and more serious; the noise becomes an issue of popular concern. Reduce noise and create a beautiful acoustic environment is an important element to improve the quality of life of the people. A microperforated panel (MPP) absorber has become widely known as the most attractive alternative for the next generation sound absorbing material [1]. The MPP is first proposed by Maa, who has established its theoretical basis and design principle [2-4]. The MPP absorber is a thin panel or membrane less than 1mm thick with perforation of less than 1% perforation ratio with air-back cavity and a rigid backing [5]. The fundamental absorbing mechanism of the MPP absorber, which is typically backed by an air cavity and a rigid wall, is Helmholtz-resonance absorption [6]. This type of absorption is mainly due to frictional loss in the air flow of the apertures [6]. With the rapid development of processing technologies and computational methods, micro-perforated panel sound absorption theory has also been further development [7-9]. But usually the single-leaf MPP sound absorbing structure is generally only one resonance absorption peak. Although, the absorption coefficient of absorption peak is able to control above 0.9, but the sound absorption bandwidth is usually limited to about two octaves [2-4]. In order to broaden the absorption frequency range, Maa has proposed a double-leaf MPP backed by a rigid-back wall with an air-cavity [10]. Recently, Asdrubali and Pispola have studied this type of absorber for its application to noise barriers [11]. This absorber is intended to produce two resonators so that a broader absorption frequency range can be obtained. The acoustical properties of a structure composed of two parallel MPP with an air-cavity between them and no rigid backing is studied numerically by Sakagami [12]. Although lots of researches have been done on broaden the absorption frequency range of MPP, it appears that no relevant reports have been given for the MPP with partitioned cavity. The main purpose of this paper will focus on the acoustic performance studies of MPP absorbers with partitioned cavity. Structure of this paper will be arranged as follows: In Section 2, sample of the MPP with partitioned cavity will be shown. In Section 3, the sound absorption performance of MPP absorber without a rigid backing will be studied. Finally, the conclusions will be given in section 4. Sample construction MPP absorbers with partitioned cavity are constructed by a MPP and a structure of partitioned cavity. MPP used is aluminum panel 100mm in diameter. Thick, porosity and aperture for the MPP are 0.8mm, 1% and 0.8mm, respectively. Figure 1 shows the structure of MPP. The structure of International Industrial Informatics and Computer Engineering Conference (IIICEC 2015) © 2015. The authors Published by Atlantis Press 345 partitioned cavity is added to MPP by attaching. Figure 2 shows the structure of MPP with partitioned cavity. The deep of partitioned cavity is 30mm. Figure 1. microperforated panel Figure 2. microperforated panel with partitioned cavity Impedance tube experiments We study the property of MPP with partitioned cavity by impedance tube experiments. Figure 3 is the test system of impedance tube. Figure 4 compare the normal incidence sound absorption coefficient of the single-leaf MPP and MPP with partitioned cavity. The deeps of backing cavity are 50mm in impedance tube experiments. Through figure 4, we find that the single-leaf MPP has one sound absorption peaks at 756 Hz. However, the MPP with partitioned cavity has two main sound absorption peaks at 536Hz and 1336Hz respectively. In addition, there also exists another peak 0.579 at 936 Hz on the structure of the MPP with partitioned cavity. The reason may be the vibration of partitioned plate. Meanwhile, the maximum sound absorption peak of MPP with partitioned cavity is 0.988 is higher than 0.960 of the single-leaf MPP’s. The sound absorption coefficient of the MPP with partitioned cavity over 0.4 in the frequency range 256-1600Hz, which is much wider than 396-1416 Hz of the single-leaf MPP. If the partitioned cavities are well designed, it will improve the sound absorption performance of the partitioned cavity. Figure 3. The test system of impedance tube