PRELIMINARY INVESTIGATION OF TWO TYPES OF HYDROPHONES UP TO 15 MHZ
In order to answer the question as to which type of hydrophone is to be recommended within the scope of the European Community for the measurements of sound fields, investigation on two different types of hydrophones were carried out: - three units of a polymer needle hydrophone and - three units of a coplanar membrane hydrophone both with an active element 1 mm in diameter. The free field sensitivities of these six hydrophones were determined in the frequency range from 1 MHz to 15 MHz by means of the two-transducer reciprocity technique at the beginning and the end of a four month period. Directional response and frequency response were determined for one device of each type using the TDS technique. Over a four month period the sensitivity measured for both types was stable within +- 0.2 dB referred to the mean value. The frequency response of the membrane hydrophones was very flat within +- 0.3 dB. Between 1 MHz and 3 MHz the needle hydrophone showed a resonance peak of less than +- 2 dB, above 3 MHz the frequency response was flat within +- 0.8 dB. The directional response of the membrane hydrophone showed large side lobes below 3 MHz, the needle hydrophone as asymmetrical main lobe below 2 MHz. Above 3 MHz the directional response of both hydrophones showed a piston-like behaviour.
Bibliographic Reference: EUR 10573 EN (1986) MF, 58 P., BFR 150, BLOW-UP COPY BFR 300, EUROFFICE, LUXEMBOURG, POB 1003
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Record Number: 1989124113300 / Last updated on: 1987-01-01
Available languages: en