Dear MARMAMers, For those interested, we wish to draw attention to a recent paper in the Journal of the Acoustical Society of America on high frequency ship noise and the potential effects on small toothed whales. We show that a broad range of vessel types produce substantial levels of noise at high frequencies, and that smaller toothed whales therefore must be considered in impact assessments of ship noise. We also show that low frequency noise bands are poor proxies for noise loads at higher frequencies, and that current low frequency indicators, such as those in the European Marine Strategy Framework Directive (MSFD), are insufficient when it comes to assessing noise effects on small toothed whales.
*"High frequency components of ship noise in shallow water with a discussion of implications for harbor porpoises (Phocoena phocoena)"* Line Hermannsen, Kristian Beedholm, Jakob Tougaard and Peter T. Madsen J. Acoust. Soc. Am. 136, 1640 (2014) URL: *http://scitation.aip.org/content/asa/journal/jasa/136/4/10.1121/1.4893908 <http://scitation.aip.org/content/asa/journal/jasa/136/4/10.1121/1.4893908>* DOI: http://dx.doi.org/10.1121/1.4893908 *Full abstract* Growing ship traffic worldwide has led to increased vessel noise with possible negative impacts on marine life. Most research has focused on low frequency components of ship noise, but for high-frequency specialists, such as the harbor porpoise (Phocoena phocoena), medium-to-high frequency noise components are likely more of a concern. To test for biologically relevant levels of medium-to-high frequency vessel noise, different types of Automatic Identification System located vessels were recorded using a broadband recording system in four heavily ship-trafficked marine habitats in Denmark. Vessel noise from a range of different ship types substantially elevated ambient noise levels across the entire recording band from 0.025 to 160 kHz at ranges between 60 and 1000 m. These ship noise levels are estimated to cause hearing range reduction of >20 dB (at 1 and 10 kHz) from ships passing at distances of 1190 m and >30 dB reduction (at 125 kHz) from ships at distances of 490 m or less. It is concluded that a diverse range of vessels produce substantial noise at high frequencies, where toothed whale hearing is most sensitive, and that vessel noise should be considered over a broad frequency range, when assessing noise effects on porpoises and other small toothed whales. A pdf version of the paper can be requested from [email protected] Best regards, Line Hermannsen
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