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Increase in effectiveness of low frequency acoustic liners by use of coupled Helmholtz resonatorsCoupling of Helmholtz resonators in a low-frequency absorber array was studied as a means for increasing the effectiveness for absorbing low-frequency core engine noise. The equations for the impedance of the coupled-resonator systems were developed in terms of uncoupled-resonator parameters, and the predicted impedance for a parallel-coupled scheme is shown to compare favorably with measurements from a test model. In addition, attenuation measurements made in a flow duct on test coupled-resonator panels are shown to compare favorably with predicted values. Finally, the parallel-coupled concept is shown to give significantly more attenuation than that of a typical uncoupled resonator array of the same total volume.
Document ID
19770036928
Document Type
Conference Paper
Authors
Dean, L. W. (United Technologies Corp. Pratt and Whitney Aircraft Group, East Hartford, Conn., United States)
Date Acquired
August 9, 2013
Publication Date
January 1, 1977
Subject Category
ACOUSTICS
Report/Patent Number
AIAA PAPER 77-19
Meeting Information
Aerospace Sciences Meeting(Los Angeles, CA)
Funding Number(s)
CONTRACT_GRANT: NAS3-18552
Distribution Limits
Public
Copyright
Other