contributions of individual ships. Indeed, the engineering tools and methodologies to achieve this are currently available, or can be developed with limited effort. For example, one of the main culprits for the noise produced by ships is propeller cavitation. Methods to reduce this cavitation include improved hull form design, improved propeller design and arrangement, wake fieldhomogenizing appendages (e.g., ducts, turbulence generators etc.), and modified propulsion concepts (e.g., twinscrew instead of single-screw. Another source of noise arises from propulsion, auxiliary and other onboard machinery. Currently available methods for reducing noise from these sources are numerous for new construction, such as the use low noise machinery, vibration isolation (also requiring isolation of associated shafting, piping, and sometimes power cables as well), and sound damping. The widespread application of these and other technical measures could easily be incorporated into new ships at a comparatively small additional cost, allowing us to meet the 30-year target. Some operational measures could also be implemented immediately to help meet the 10-year target. Making commercial shipping quieter on a ship-by-ship basis would therefore result in an overall increase in potential communication/hearing ranges for marine mammals. Additionally, there may very well be some associated benefits to the industry in terms of increasing efficiency and reduced maintenance costs from the use of noise-reduction technologies, although it is still too early to be certain. However, shipping noise is a trans-boundary, international issue, and any additional construction costs, although likely to be small, could provide those countries not implementing them with a competitive advantage. The participants of the workshop realized this and called for the coordination of action at the international level, i.e. by the International Maritime Organization and its members. Commercial shipping is the most efficient way of transporting goods in terms of carbon produced per ton moved per mile. Provided that these large vessels can be made quieter without increasing carbon production, which appears to be possible, this would further increase the environmental credentials of the industry. It will also be nice to know, next time you pass a whale, that you're part of an effort to improve their environment and allow them to live literally in peace and quiet.
About the Author
Andrew J. Wright is an independent marine mammal scientist with experience working on noise-related policy within and outside the U.S. Government. Since completing a M.Sc. at the University of Wales, Bangor in 2004, he has consulted for U.S. governmental agencies and non-profits predominantly on assessing the acoustic impacts of human activities on marine mammals. He has coorganized three workshops on the issue in his current role for Okeanos - Stiftung für das Meer (Foundation for the Sea: http://www.okeanos-stiftung.org/) and can be reached at marinebrit@gmail.com.
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Marine Technology Reporter 25
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