Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/6615
Title: Sound propagation in and low frequency noise absorption by helium-filled porous material
Authors: Choy, YS 
Huang, L
Wang, C
Keywords: Acoustic wave absorption
Acoustic wave propagation
Acoustics
Biological materials
Gas absorption
Helium
Hydroxylation
Porosity
Porous materials
Radioactivity
Sound insulating materials
Thermal noise
Issue Date: Dec-2009
Publisher: Acoustical Society of America
Source: Journal of the Acoustical Society of America, Dec. 2009, v. 126, no. 6, p. 3008-3019 How to cite?
Journal: Journal of the Acoustical Society of America 
Abstract: Low-frequency noise is difficult to deal with by traditional porous material due to its inherent high acoustic impedance. This study seeks to extend the effective range of sound absorption to lower frequencies by filling a low density gas, such as helium, in the porous material. Compared with conventional air-filled absorptionmaterial, the helium-filled porous material has a much reduced characteristic impedance; hence, a good impedance matching with pure air becomes more feasible at low frequencies. The acoustic properties of a series of helium-filled porous materials are investigated with a specially designed test rig. The characteristic of the sound propagation in a helium-filled porous material is established and validated experimentally. Based on the measuredacoustic properties, the sound absorption performance of a helium-filled absorber (HA) of finite thickness is studied numerically as well as experimentally. For a random incidence field, the HA is found to perform much better than the air-filled absorber at low frequencies. The main advantage of HA lies in the middle range of oblique incidence angles where wave refraction in the absorber enhances sound absorption. The advantage of HA as duct lining is demonstrated both numerically and experimentally.
URI: http://hdl.handle.net/10397/6615
ISSN: 0001-4966
DOI: 10.1121/1.3257182
Rights: Copyright 2009 Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.
The following article appeared in Choy, Y. S., Huang, L., & Wang, C. (2009). Sound propagation in and low frequency noise absorption by helium-filled porous material. Journal of the Acoustical Society of America, 126(6), 3008-3019 and may be found at http://scitation.aip.org/content/asa/journal/jasa/126/6/10.1121/1.3257182.
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