過去の学会誌一覧

Vol.31 No.3 通巻115号 (2004年/平成16年)

表彰 7(133)
研究 Design of a Small Fisheries Research Vessel with Low Level of Underwater-Radiated Noise
Yasuo YOSHIMURA (Graduate School of Fisheries Sciences, Hokkaido University), Yasunari KOYANAGI (Division of Fisheries Consultant, Kyokuyo Co., Ltd.)
Abstract:
It is important for a fisheries research vessel to reduce the underwater-radiated noise. In 1995, the International Council for the Exploration of the Sea (ICES) firstly recommended the maximum noise level for research vessels to ensure the acoustic research works and to prevent the fish reaction against the noise 1). Since then, it has been the world standard for the design of fisheries research vessels. For a small size vessel, however, it is very difficult to achieve the recommendations because of not enough space or capacity to make sound insulations. Moreover, the Froude number (Fn) of such small vessels tends to be higher than that of the larger vessels. Since the higher Froude number of the operating condition causes the large wave-making resistance, both propeller thrust and occurrence of cavitation increase, which tends to result in the higher level of underwater-radiated noise. Meanwhile, the fisheries research-cost can be reduced by using a small vessel, because not only the construction and operation cost, but also maintenance cost become lower than those of a large vessel. It would be desirable and efficient if a small vessel could satisfy the ICES's recommendation in place of a large research vessel.
In this paper, the authors propose a design method for a small research vessel to reduce the underwater-radiated noise level. Utilizing this method, a small fisheries research vessel whose capacity is 290 GT and length is 33.5 m has been designed. From the sea trials after the construction, it has been proved successfully that the underwaterradiated noise level is the world lowest class at 10 knots (Fn=0.28) of researching speed and still satisfies the ICES's recommendation even in 11.6 knots (Fn=0.33) of the high-speed region.
Yasuo YOSHIMURA, Yasunari KOYANAGI 11(137)
ウェーブレット・インテンシティ法によるソーナー流体雑音の方向性の解析
Analysis of Sonar Flow Noise Directivity by the Wavelet Intensity Method
*1 Takaaki MUSHA (5th Research Center, TRDI, Japan Defense Agency)
*2 Tatsuya KUMAZAWA (Technical Department, TRDI, Japan Defense Agency)
Abstract :
In the field of acoustic intensity measurement, the two microphone measurement technique by using the FFT method is widely used for obtaining time averaged sound intensity. However this method can not be applied for measuring time-dependent process of energy transfer in an acoustic field of flow noise due to its nonstationary characteristics. In this article, we propose the instantaneous intensity analysis method by using the harmonic wavelet transform. The analysis result of the data obtained by the measurement on ship reveals that the direction of flow induced sonar noise shows strong fluctuations but most of them are arrived from both directions of up and down quarters of the sonar array at high speeds.
武捨 貴昭,熊沢 達也 20(146)
2003年度第2回シンポジウム発表要旨 2003年水中防衛技術学会(UDT)報告
(その1)UDT Europe 2003(UDT Korea 2002を含む)の概要
水野 鉄臣 28(154)
(その2)ソーナーシステムについて 深見 明久 33(159)
(その3)UUVについて 後藤 英親 38(164)
(その4)海洋音響環境について 尾崎 俊二 43(169)
レポート 第13回技術講習会報告 松廣 紀夫 48(174)
第18回国際音響学会議概要報告 鎌田 弘志 49(175)
随想 水産音響黎明期の思い出 間庭 愛信 53(179)
Paper Index 土屋 健伸 57(183)
海洋音響学会資料 59(185)
会記事 81(207)