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2 TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2 2012

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Feasibility on Infrared Detection of Cetaceans for Avoiding Collision with Hydrofoil

Yonehara Y., Kagami L., Yamada H., Kato H., Terada M., Okada S.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2012

Vol. 6, no. 1

149--154

To achieve safer navigation without sudden collisions with large cetaceans at high speed boats such as the hydrofoil, we examined its feasibility of an installation of the infrared camera. Because any ceta-ceans are of air-breathing animals, it is theoretically expected that they can be potentially detected through imaging of the infrared cameras. Thus, we examined the feasibility of detection with aiming at sperm whales in waters off Chichijima Islands (27°4'N, 142°13'E), Japan. Through the experiment, it was revealed that sperm whales could be detected stably within 200m, and detectable cue were blow, back body and fluke tails. However, boats and waves were also detected as noise images. Especially, waves greatly resemble the whale back bodies. Although potential of the infrared camera was confirmed, there are still necessities of further ex-periments including ones conducting at different temperate waters, to successfully install the infrared camera for earlier finding of large cetaceans.

Estimation on Audibility of Large Cetaceans for Improvement of the Under Water Speaker

Yamada H., Kagami L., Yonehara Y., Matsunaga H., Kato H., Terada M., Takahashi R., Okanoya K., Kawamoto T.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2012

Vol. 6, no. 4

589--593

In order to avoid collisions between the hydrofoil (HF) and cetaceans, the Under Water Speaker (UWS) has been installed on the HF. Because of its potential in utility, we tried to improve the UWS to minimize the risk of the collisions. Under our project, we examined three subprojects; 1) Analyzing the characteristics of the HF underwater noise; 2) Assessing audibility of major large cetaceans by measuring their vocalizations and 3) An anatomical prediction of the audible range by examining the cochlear basal membrane. Through the analyses, it was identified that the noise produced by the HF was a broad-band noise with approximately 150dB re 1μPa-m.That noise level was lower than those of larger boats suggesting difficulties for cetaceans in sensing approach of the vessels. In addition, analysis of their vocalizations and anatomical obervation indicated that dominant frequency of their audible range was lower than signals produced by the existing UWS.