The acoustic characteristics of a point-reacting duct liner that consists of a porous facing sheet backed by cellular cavities are derived by examining the wave propagation within the liner. The relation between the derived expression for the liner acoustic admittance and a semi-empirical formula that is widely used in the literature is discussed. The influence of the liner on acoustic propagation in a duct is examined for the case of a plane duct that carries a uniform mean flow. Numerical results for the attenuation rates vs. frequency are presented. These results. are of three types: (1) comparisons with previously published results for no backing cavity and no mean flow are made, and these results are extended to include the effects of the mean flow; (2) results of parametric variations of the liner dimensions are presented to assess the relative influence of the facing-sheet thickness and the cavity depth; (3) results from the derived expression for liner specific admittance and from the semi-empirical formula are compared in order to determine the significance of the wave propagation within the porous material and to determine the range of validity of the semi-empirical formula. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/70568 |
| Date | January 1974 |
| Creators | Shaker, B. S. |
| Contributors | Engineering Science and Mechanics |
| Publisher | Virginia Polytechnic Institute and State University |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | v, 36 leaves, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 33352175 |
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