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Experimental estimation of in vacuo structural admittance using random sources in a non-anechoic room

TitleExperimental estimation of in vacuo structural admittance using random sources in a non-anechoic room
Publication TypeJournal Article
Year of Publication2017
AuthorsWilliams E.G, Tippmann J.D, Rakotonarivo S.T, Waters Z.J, Roux P, Kuperman WA
JournalJournal of the Acoustical Society of America
Date Published2017/07
Type of ArticleArticle
ISBN Number0001-4966
Accession NumberWOS:000405656700026
Keywordsimpedance; scattering

Identification of unexploded ordinance buried in the sediment in the littoral waters throughout the world is a problem of great concern. When illuminated by low-frequency sonar some of these targets exhibit an elastic response that can be used to identify them. This elastic behavior is embodied and identified by a quantity called the in vacuo structural admittance matrix Y-s, a relationship between the sonar-induced forces and resulting vibration on its surface. When it is known it can be combined with surface impedances to predict the three-dimensional bistatic scattering in any fluid-like media and for any burial state (depth and orientation). At the heart of this is the measurement of Ys and it is demonstrated in this paper that this can be accomplished by studying the target in a simple (acoustically unaltered) in-air laboratory environment. The target chosen in this study is a thick spherical shell that was illuminated by a nearly spatially isotropic array of remote loudspeakers. Ys is constructed from ensemble averages of the cross-correlations of eight collocated accelerometers and microphones placed on the surface of the object. The structural admittance determined from the data showed excellent agreement with theory.

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