Underwater Anechoic Tank Linings
NAVAL ORDNANCE LAB WHITE OAK MD
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An investigation of structured linings employing the principle of a gradual impedance transition from water to a sound-absorbent material has been made. Prototype metal-loaded butyl rubber linings have been developed which consist of a molded panel of closely-packed right circular cones and an integral backing layer. Reflection characteristics were measured for three samples having this structure but differing in the type of metal loading. In addition, measurements were made on plane samples of each type of rubber, and also on samples of Fafnir, Insulkrete, and canvas. The technique consisted of subjecting the test panel to normally incident pulse-modulated sound and measuring the reflected sound pressure with a rotating probe hydrophone. The test panel was backed by a perfectly-reflecting flat plate which also was used as a reference reflector. By this method it was possible to obtain the reflected sound intensity as a function of polar angle reflectivity pattern and from this the scattering and absorption were computed.
- Test Facilities, Equipment and Methods