The Journal of the Marine Acoustics Society of Japan
Online ISSN : 1881-6819
Print ISSN : 0916-5835
ISSN-L : 0916-5835
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Volume 19, Issue 3
Displaying 1-2 of 2 articles from this issue
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  • Piezoelectric rubber transducer
    Part2 Suppression of side lobes using shape shading.
    Akio HASEGAWA, Toshiaki KIKUCHI
    1992 Volume 19 Issue 3 Pages 133-146
    Published: July 01, 1992
    Released on J-STAGE: March 02, 2011
    DOIhttps://doi.org/10.3135/jmasj.19.133
    JOURNAL FREE ACCESS
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    Suppression of side lobes can be accomplished by utilizing Dolph-Chebyshev amplitude shading. Research on shape shading is seldom found because of the great difficulty in cutting of PZT ceramics. Recently, a piezorubber sheet consisting of piezoelectric ceramic particles and chloroprene rubber has been developed. Since this material is quite soft compared with PZT ceramics, it is very useful for research in shape shading. In this paper, aperture functions, originally applied to the design of FIR digital filters, are shown to also be successfully applied for suppression of side lobes in hydrophones. Test hydrophones are constructed by shading a piezorubber sheet in the form of the aperture functions. It is clarified both experimentally and theoretically that some hydrophones such as Hamming and Hamming-like Kaiser windows suppress side lobes to less than -30dB.
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  • Separation into incident and reflected waves using two-hydrophone and three-hydrophone methods.
    Satoshi YOSHII, Akio HASEGAWA, Toshiaki KIKUCHI
    1992 Volume 19 Issue 3 Pages 147-155
    Published: July 01, 1992
    Released on J-STAGE: March 02, 2011
    DOIhttps://doi.org/10.3135/jmasj.19.147
    JOURNAL FREE ACCESS
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    The separation of a standing wave field in air into incident and reflected waves is possible with a wave separator, employing two-microphones and some delay units. This separation technique is called a two-microphone method. The two-microphone method is shown to also be successfully applied for water-bone sound waves. A new three-hydrophone method which does not need to consider the sound velocity factor is proposed. In this method, it is sufficient to measure only complex sound pressures at three points. Experimental results have verified the theoretical predictions on the separation of the standing wave in water.
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