| 摘要 |
PURPOSE:To attain broad band for the sensitivity frequency characteristic by forming a recessed part to a face opposite to a face bonded with a piezoelectric ceramic acoustic matching layer so as to form the piezoelectric ceramic as a planoconcave shape. CONSTITUTION:One side of a circular piezoelectric ceramic 7 is made flat and the opposite side to the flat face is shaped as a planoconcave formed with a recessed part 7a and the thickness of the peripheral part and the center is decided so that the resonance frequency reaches a prescribed frequency range. The acoustic matching layer 2 is bonded to the falt face of the piezoelectric ceramic 7, and the piezoelectric ceramic 7 and the acoustic matching layer 2 are contained in the sound absorbing member 3 whose one face is opened and a container 4 and the entire part is molded incorporatedly by a mold member 6.
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