| 摘要 |
PURPOSE:To improve the SN ratio of transmitting and receiving signals, by providing a shield wall for underwater noise due to a propelling mechanism on the outer surface of a ship bottom between an ultrasonic transmitter/receiver and the propelling mechanism. CONSTITUTION:The bottom 4 of a fishing boat 1 is provided with a shield wall 3 made of metal, a synthetic resin, wood or the like as located on a keel 6 in the outer surface of the bottom between a propelling mechanism 5 and an ultrasonic wave transmitter/receiver 2. This shield wall 3 is so arranged as to be almost triangular viewed from the side thereof with the top of the triangle thereof most separated from the outer surface 4 of the bottom and connected successively to the ultrasonic transmitter/receiver 2. Thus, underwater noise due to the propelling mechanism 5 and vibration noise or the like of other engines are propagated underwater and intercepted with the shield wall 3 to be prevented from propagation direct to the ultrasonic wave transmitter/ receiver 2. This process improves the SN ratio.
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