Small Hydrophone that is Directional at Low Frequencies.
DEPARTMENT OF THE NAVY WASHINGTON DC
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This document discloses a small hydrophone that is directional at low frequencies. Directional characteristics are achieved by making the device small compared to the wavelength of the wave detected by exploiting the directionality of Rayleigh scattering. The hydrophone includes two small-diameter piezoceramic shells, one larger than the other, mounted in rubber rings a fixed distance from each other with their centers on the same horizontal plane within a long, expanded-metal cylinder. The metal cylinder is covered by a rubber boot to ensure a water tight housing. Both hydrophones are omnidirectional in the horizontal plane and each has a sensitivity that is constant over the desired frequency range. The device can be used for detecting low-frequency sound waves in a fluid medium. A similar arrangement of antennas can be used to detect electromagnetic waves in free space or a dielectric medium. Author
- Acoustic Detection and Detectors