SIMULATION STUDY OF A SYSTEM FOR MEASURING DIRECTIVITY INDEX.
NAVAL RESEARCH LAB WASHINGTON D C
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In a proposed directivity-index-measuring system, a semicircular array of hydrophones samples the acoustic power output of an underwater electroacoustic transducer associated analog electronic circuitry and a digital computer yield a number representing the directivity index. The response of such a system to changes in geometric distribution of sampling points, number of points sampled, and complexity of directivity pattern has been studied by means of a computer-simulated model. Results show that the specified accuracy can be exceeded by using 11 hydrophones arranged to sample 396 equal areas of a spherical surface when the source is a plane, circular piston ka or 10 radiating in an infinite baffle. Limits consistent with the required accuracy also were established for potential sources of error within the system projector misalignment, finite sampling time, dynamic range, and conversion nonlinearity. Author