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Technical Brief

Investigation of a Compound Perforated Panel Absorber With Backing Cavities Partially Filled With Polymer Materials

[+] Author and Article Information
C. Q. Wang

Department of Mechanical Engineering,
The University of Hong Kong,
Pokfulam Road,
Hong Kong, China
e-mails: cqwang@hku.hk; chunqi76@gmail.com

Y. S. Choy

Department of Mechanical Engineering,
The Hong Kong Polytechnic University,
Hung Hom,
Hong Kong, China
e-mail: mmyschoy@polyu.edu.hk

1Corresponding author.

Contributed by the Noise Control and Acoustics Division of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received November 17, 2014; final manuscript received February 4, 2015; published online March 13, 2015. Assoc. Editor: Liang-Wu Cai.

J. Vib. Acoust 137(4), 044501 (Aug 01, 2015) (6 pages) Paper No: VIB-14-1438; doi: 10.1115/1.4029771 History: Received November 17, 2014; Revised February 04, 2015; Online March 13, 2015

The paper concerns the sound absorption performance of a compound absorber which consists of a parallel arrangement of multiple perforated panel absorbers of different backing cavity depths partially filled with poroelastic polymer materials. Three polymer materials are considered: expandable polystyrene (EPS) foam, polymethacrylimide (PMI) foam, and polyester fiber. The normal incidence sound absorption coefficients of the compound panel absorber are tested experimentally. Results show that the former two foams can achieve similar absorption performance to the rigid cavity configuration, while the resonances shift to lower frequencies due to the changes of effective cavity depths. It is also found that the additional attenuation by polymer foams may improve sound absorption, but the effect is marginal. For polyester fiber, results show that it performs more like a single perforated panel absorber. Finite element simulation of the compound panel absorber is also discussed, and good agreement is observed between simulated and experimental results.

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Figures

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Fig. 1

Schematic of the compound perforated panel absorber with different cavity depths. (a) Rigid configuration and (b) Polymer-based configuration.

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Fig. 2

Photo of the prototype compound perforated panel absorber

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Fig. 3

Comparison of the measured and predicted normal incidence sound absorption coefficients of the compound absorber with rigid configuration

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Fig. 4

Measured normal incidence sound absorption coefficient of the compound absorber based on EPS foam. Default cavity: D1= 48 mm, D2= 98 mm, and D3= 24 mm; shallow cavity: D1= 42 mm, D2= 98 mm, and D3= 14 mm. Results of the corresponding rigid configuration are also shown for comparison.

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Fig. 5

Measured normal incidence sound absorption coefficient of the compound absorber based on PMI foam. Results of the corresponding rigid configuration are also shown for comparison.

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Fig. 6

Measured normal incidence sound absorption coefficient of the compound absorber based on polyester fiber. Results of the rigid-configuration are for comparison. The cavity geometry is specified in Eq. (8). The uniform cavity has a constant depth D = 98 mm.

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Fig. 7

Comparison of the measured and predicted normal incidence sound absorption coefficients of the compound absorber based on polyester fiber

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Fig. 8

The measured acoustic impedance at the surfaces of two pieces of EPS foam backed by rigid walls

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Fig. 9

The predicted normal incidence sound absorption coefficients of the compound absorber based on EPS foam. (a) Comparison of the measured results and numerical predictions and (b) variation of the predicted absorption performance by neglecting the acoustic resistance of the EPS foam.

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