200kc音響測深機の装備に関する研究(日本航海学会第24回講演会)

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タイトル別名
  • Study on the Installation of 200 kc Echo-sounder
  • 200kC音響測深機の装備に関する研究
  • 200kC オンキョウ ソクシンキ ノ ソウビ ニ カンスル ケンキュウ

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It is often observed that some decrease occurs in the sounding capacity of echo sounder when a shen runs at fast speed. The main reason of such decerase is thought that the ultrasonic wave transmitted from the transducer installed on the bottom is disturbed by the bubble layer occuring under the ship bottom. The ultrasonic wave is attenuated by the bubble layer, and its attenuation decreases as the frequency of ultrasonic wave increases, as clarified by the Laboratory as well as by field experiments. In order to obtain data for a actual ship, we installed two types of echo-sounder of 13 kc. and 200 kc in frequency in a 220 ton steel fishing research boat and observed the influence of bubble layer on the echosounder. The transducers of echo-sounders were installed in the same condition at ship bottom as shown in Fig.2. The result shows that the 200 kc echo-sounder was not affected by the bubble layer under the condition of slight sea and ship speed at 11 kt. But in the case of 13 kc echo-sounder under the same coditions, attenuation was observed in the ultrasonic wave by more than 10 db and the increase of noise reached as much as 30 db. In this way it has been found that the sounding capacity of a 13 kc echo-sounder falls as low as 400 meters even though it registers at 4, 000 meters when the ship is in stop. From these data it may be concluded that a 200 kc echo-sounder is sufficient for the echo-sounding up to 500 meters and that for the echo-sounding abovs 500 meters it is necessary to use an echo-sounder of lower frequency, such as 13 kc. In the latter case, a great care must be taken for the selection of position where the transducer be installed and for the technique of such installation so as to avoid the harmful influence of bubble layer.

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