| 摘要 |
PROBLEM TO BE SOLVED: To provide a receiving device excellent in noise resistance by arranging a recess/projection part in either of both vibrating plates, and setting an angle to a vibrating plate surface of respective inclined faces to the outer periphery from the surface center of the vibrating plates to an angle unreceivable to a receiver even if an ultrasonic wave from a transmitter is reflected by the receiver and is also reflected by the transmitter. SOLUTION: A recess/projection part 11 is arranged on one surface of vibrating plates 1b, 2b. An angle to a surface of the vibrating plates 1b, 2b of respective inclined faces 111 turning in the outer peripheral direction from the surface center of the vibrating plates 1b, 2b is set to an angle unreceivable to the vibrating plate 2b of a receiver 2 even if an ultrasonic wave transmitted from a transmitter 1 is reflected by the receiver 2 and is also reflected by the transmitter 1. Actually, when a distance between the ultrasonic wave transmitter and receiver is denoted by L and a radius of the ultrasonic wave transmitter and receiver is denoted by R, an angle of the inclined faces 111 to the surface of the vibrating plates 1b, 2b is set toα=174 tan-1 (L/R), thereby reduces a reflected wave to reduce noise.
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