Evaluation of a standing wave system for determining the presence and acoustic effect of microbubbles near the sea surface.
Keller, Douglas George
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That bubbles affect sound propagation in the ocean has long been known. However,, quantitative data on the concentrations and distribution of bubbles near the surface of the ocean is not available. A one-dimensional, high Q, standing wave system was constructed and evaluated to determine bubble concentrations by measuring the effect of bubbles on the system Q's. It was tested to depths of 40 feet and in the frequency range of 10-100 kHz. This system used a mylar electrostatic transducer as the sound source and also as one of the reflectors. System Q's of 3500 were obtained. It was possible to measure attenuation to t 0,019 db/m above 20 kHz. Hydrostatic pressure caused variations in the face of the transducer thereby making the system unstable. The mylar transducer is therefore unsuitable for use as both source and reflector. Initial investigations made into using the mylar transducer to externally excite a reflector-reflector system are also described.
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