APPARATUS FOR THE MEASUREMENT OF THE SCATTERING OF SOUND.
HARVARD UNIV CAMBRIDGE MA ACOUSTICS RESEARCH LAB
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This report describes apparatus built to measure the scattering of sound by objects of size comparable with the wavelength of the sound, and of acoustic constants comparable with those of the medium. For experimental convenience, it was decided to make the measurements in water, and the method of using short pulses of sound is employed in order to make the measurements in the confined space of a tank without interference from sound reflections at the walls of the tank. The measurements are made at a frequency of 1 mcs, using pulses from 16 to 64 microseconds in length. A method of frequency-modulating the pulse repetition rate is used to prevent interference with the measurements by sound reverberating in the tank. The hydrophones, the tank and the apparatus for supporting the hydrophones, and the electronic equipment are described herein, and some remarks are included on the performance of the apparatus, based on preliminary measurements. A few scattering patterns are included as examples of the measurements made so far. Author
- Test Facilities, Equipment and Methods