| 摘要 |
PURPOSE:To form a wide-band and horizontally nondirectional ultrasonic transmitter-receiver by providing at least one cylindrical or annular synthetic resin member whose thickness is about a quarter as large as the wavelength of underwater sound to the outer periphery of piezoelectric ceramic. CONSTITUTION:The cylindrical piezoelectric ceramic 6 is clamped with flanges 8a and 8b across spacers 7a and 7b and the cylindrical resin member 9 is provided to the outer periphery. The synthetic resin member 9 is about a quarter as thick as the wavelength of underwater sound, and its acoustic impedance is larger than the acoustic impedance ZL of water and smaller than the acoustic impedance ZO of the piezoelectric ceramic 6. Namely, when the acoustic impedance Z is the geometric mean (ZL.ZO)<1/2> between the acoustic impedance ZO and acoustic impedance ZL, the piezoelectric ceramic and water are matched with each other completely and wide band frequency characteristics are obtained.
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