Publications

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2013
Roth, EH, Schmidt V, Hildebrand JA, Wiggins SM.  2013.  Underwater radiated noise levels of a research icebreaker in the central Arctic Ocean. Journal of the Acoustical Society of America. 133:1971-1980.   10.1121/1.4790356   AbstractWebsite

U.S. Coast Guard Cutter Healy's underwater radiated noise signature was characterized in the central Arctic Ocean during different types of ice-breaking operations. Propulsion modes included transit in variable ice cover, breaking heavy ice with backing-and-ramming maneuvers, and dynamic positioning with the bow thruster in operation. Compared to open-water transit, Healy's noise signature increased approximately 10 dB between 20 Hz and 2 kHz when breaking ice. The highest noise levels resulted while the ship was engaged in backing-and-ramming maneuvers, owing to cavitation when operating the propellers astern or in opposing directions. In frequency bands centered near 10, 50, and 100 Hz, source levels reached 190-200 dB re: 1 mu Pa at 1m (full octave band) during ice-breaking operations. (C) 2013 Acoustical Society of America.

2012
Roth, EH, Hildebrand JA, Wiggins SM, Ross D.  2012.  Underwater ambient noise on the Chukchi Sea continental slope from 2006-2009. Journal of the Acoustical Society of America. 131:104-110.   10.1121/1.3664096   AbstractWebsite

From September 2006 to June 2009, an autonomous acoustic recorder measured ambient noise north of Barrow, Alaska on the continental slope at 235 m depth, between the Chukchi and Beaufort Seas. Mean monthly spectrum levels, selected to exclude impulsive events, show that months with open-water had the highest noise levels (80-83 dB re: 1 mu Pa-2/Hz at 20-50 Hz), months with ice coverage had lower spectral levels (70 dB at 50 Hz), and months with both ice cover and low wind speeds had the lowest noise levels (65 dB at 50 Hz). During ice covered periods in winter-spring there was significant transient energy between 10 and 100 Hz from ice fracture events. During ice covered periods in late spring there were significantly fewer transient events. Ambient noise increased with wind speed by similar to 1 dB/m/s for relatively open-water (0%-25% ice cover) and by similar to 0.5 dB/m/s for nearly complete ice cover (> 75%). In September and early October for all years, mean noise levels were elevated by 2-8 dB due to the presence of seismic surveys in the Chukchi and Beaufort Seas. (C) 2012 Acoustical Society of America. [DOI: 10.1121/1.3664096]

McKenna, MF, Ross D, Wiggins SM, Hildebrand JA.  2012.  Underwater radiated noise from modern commercial ships. The Journal of the Acoustical Society of America. 131:92-103.   10.1121/1.3664100   AbstractWebsite

Underwater radiated noise measurements for seven types of modern commercial ships during normal operating conditions are presented. Calibrated acoustic data (<1000 Hz) from an autonomous seafloor-mounted acoustic recorder were combined with ship passage information from the Automatic Identification System. This approach allowed for detailed measurements (i.e., source level, sound exposure level, and transmission range) on ships of opportunity. A key result was different acoustic levels and spectral shapes observed from different ship-types. A 54 kGT container ship had the highest broadband source level at 188 dB re 1 mu Pa@1m; a 26 kGT chemical tanker had the lowest at 177 dB re 1 mu Pa@1m. Bulk carriers had higher source levels near 100 Hz, while container ship and tanker noise was predominantly below 40 Hz. Simple models to predict source levels of modern merchant ships as a group from particular ship characteristics (e. g., length, gross tonnage, and speed) were not possible given individual ship-type differences. Furthermore, ship noise was observed to radiate asymmetrically. Stern aspect noise levels are 5 to 10 dB higher than bow aspect noise levels. Collectively, these results emphasize the importance of including modern ship-types in quantifying shipping noise for predictive models of global, regional, and local marine environments. (C) 2012 Acoustical Society of America. [DOI: 10.1121/1.3664100]