Influence of Shear Modulus on the Behavior of Acoustically Transparent Materials.
Interim rept. 9 Jan 84-12 Jan 85,
NAVAL RESEARCH LAB WASHINGTON DC
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Materials are under construction that match the density, rho and dilatational sound speed, c as closely as possible to the values of seawater, while maintaining sufficient rigidity to serve for structural purposes. The demand for rigidity implies a larger shear modulus than is typical for the usual rho-c elastomers. Matching of density and sound speed results in transparency for fluids only the finite shear modulus in a solid admits the presence of a shear wave, which causes deviation from ideal rho-c behavior. In this report the effect is analyzed of a finite shear modulus on the reflection of plane waves by an infinite plate of the rho-c material. Examples are given of the reflection coefficient as a function of incidence angle for various combinations of density and sound speed close to ideal, and various ratios of plate thickness to dilatational wavelength. The effect of a finite loss factor in the shear modulus is known. Keywords Reflection of acoustic waves.
- Acoustic Detection and Detectors