| 摘要 |
PURPOSE:To improve the efficiency of electroacoustic transducing by providing a signal passing band between two resonance characteristics of an oscillator, and thus obtaining a wide band characteristics. CONSTITUTION:Between a front mass 31 and a rear mass 33 made of a high- rigidity material, annular piezoelectric ceramics members 32 polarized previously in a center-axis direction (as shown by arrows) are connected electrically in parallel and in combination so that the polarization directions of adjacent ceramics members are opposite. Then, a bolt 34 and a nut 35 made of high tension alloy apply a compressive stress to the ceramics members 32. The length (aa'- bb') of the mass 31 should be (C/4f0)X0.8-(C/4f0)X1.2, where when a part bb'- cc' including the ceramics members 32 and rear mass 33 resonates with a half wavelength, the resonance frequency is f0 and the speed of sound in the front mass 31 is C. Further, its acoustic impedance density is limited to 2.1X10<6>- 6.5X10<6>kg/m<2>.sec. |
