The Acoustic Wave Guide. II. Some Specific Normal Acoustic Impedance Measurements of Typical Porous Surfaces with Respect to Normally and Obliquely Incident Waves
作者:
E. A. G. Shaw,
期刊:
The Journal of the Acoustical Society of America
(AIP Available online 1953)
卷期:
Volume 25,
issue 2
页码: 231-235
ISSN:0001-4966
年代: 1953
DOI:10.1121/1.1907026
出版商: Acoustical Society of America
数据来源: AIP
摘要:
The experimental techniques described in Part I have been applied to the measurement of some acoustic properties of specimens of rockwool, hairfelt and acoustic tile, backed by a rigid wall. The more porous surfaces show substantial increases resistance at oblique angles of incidence, an increase of nearly 100 percent at 80° a incidence being observed in one case; smaller changes in reactance also occur. The absorption coefficients corresponding to impedance measurements at oblique incidence are compared with those “predicted” from normal incidence impedance measurements and significant differences are found. The measurement of surfaces having structure of finite dimensions is discussed with particular reference to an acoustic tile specimen, the impedance of which varies only slightly with angle of incidence. In some cases slight scattering of acoustic energy from one mode to another provides evidence of lack of uniformity of impedance over the surface of the specimen.
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