Journal
APPLIED ACOUSTICS
Volume 159, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.apacoust.2019.107119
Keywords
Micro-perforated panel; Grazing flow; Experimental study; Impedance formulae validation; Sound absorption behavior
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Funding
- Research Grant Council of the Hong Kong SAR [PolyU 152036/18E]
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Micro-perforated panels (MPPs) are widely used for broadband sound absorptions. In the presence of flow, MPPs exhibit complex behavior, which can be characterized by their surface acoustic impedance. Compared with no-flow conditions, studies on MPPs in low-speed grazing flow, especially experimental ones, are scarce. This paper reports an experimental study on the acoustic impedance of MPPs inside a flow duct with grazing incident waves. Through comparisons with experimentally educed impedance data under various flow velocities, the full set of acoustic impedance formulae proposed in our previous work is validated, which is further used to investigate the sound absorptions of a MPP liner with honeycomb backing. Analyses on the sound absorption coefficient curves show that the presence of the grazing flow shifts the absorption peak to a higher frequency, widens the bandwidth and alters the maximum absorption value. Different from the no-flow conditions, however, the peak frequency is found to be less sensitive to the variation of the hole diameter when a flow is present. (C) 2019 Elsevier Ltd. All rights reserved.
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