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Repellence Effect of the New Sound for Underwater Speaker of Hydrofoil

Nakashima T., Kobayashi N., Yamada H., Katsumata T., Yoshida R., Kato H., Okabe H., Kawazu I., Yanase Y., Omine M., Terada M., Sugioka H., Kyo M.

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

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2015

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Vol. 9, no. 2

207--211

EN

In order to prevent hydrofoil colliding with cetaceans, the underwater speaker (UWS) has been installed to repel cetaceans. Yamada et al. (2012) analyzed and devised the UWS sound as it fits the cetaceans' acoustic properties to prevent the collision furthermore. The new UWS sound was devised and synthesized by Yamada et al. (2015) with expectation of avoiding collision with large cetaceans (Patent applied for, JP2014-171411). In this research project, the new UWS sound was investigated by the playback experiment on humpback whale (Megaptera novaeangliae) and by sighting survey in the actual hydrofoil shipping service route. As a result, a physiological and behavioral change of the humpback whale was observed in the playback experiment of the new UWS sound, and the chance of hydrofoil encountering cetaceans of the new UWS sound was smaller than that of the previous UWS sound. Therefore, the improvement of the new UWS sound was confirmed. Lastly, we wish this research project would contribute toward the safer cruise of hydrofoil in the future.

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Towards Safer Navigation of Hydrofoils: Avoiding Sudden Collisions with Cetaceans

Kato H., Yamada H., Shakata K., Odagawa A., Kagami R., Yonehara Y., Terada M., Sakuma K., Mori H., Tanaka I., Sugioka H., Kyo M.

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

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2012

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Vol. 6, no. 1

143--147

EN

Recently, sudden collisions between large cetaceans and high-speed hydrofoils have become problematic to Japanese sea transport in some localities. We therefore initiated a project to investigate ap-proaches for minimizing risk to both ships and cetaceans. Under the present project, the following three sub-projects are underway: clarifying which whale species are found near sea routes and determining their season-al variations; identifying whale species that have a high collision risk; and determining the unique acoustic characteristics of high-collision-risk cetaceans for the improvement of underwater speakers (UWS). By con-ducting acoustic surveys using novel methods, including an anatomical approach based on characteristics of the inner ear, the aim of this project is to accurately estimate the audible range of species with a high collision risk and improve the sounds generated by the UWS. Thus far, we have identified the cetacean species at high-risk in two major sea routes. In the next phase of the study we plan to develop an imaging system that recog-nizes a cetacean's unique blow using an infrared camera, in an attempt to warn of the approach of high-collision-risk whale species at an early stage by sounding an alarm.

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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

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2012

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Vol. 6, no. 1

149--154

EN

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.

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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

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2012

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Vol. 6, no. 4

589--593

EN

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.