Composite Training Unit Exercises and Joint Task ... - Govsupport.us

CD-086-06, Navy Training ExercisesSouthern CaliforniaPage 23equipment) occurred. For each frequency, the percentage of sessions inwhich behavioral alterations occurred was calculated as a function ofreceived noise SPL. By pooling data across individuals and testfrequencies, respective SPL levels coincident with responses by 25, 50,and 75 percent behavioral alteration were documented. 190 dB re 1 mPa(SPL) is the point at which 50 percent of the animals exposed to 3, 10,and 20 kHz tones were deemed to respond with some behavioralalteration, and the threshold that the Navy originally proposed forsub-TTS behavioral disturbance.(2) Nowacek et al. (2004) conducted controlled exposure experimentson North Atlantic right whales using ship noise, social sounds of conspecifics,and an alerting stimulus (frequency modulated tonal signalsbetween 500 Hz and 4.5 kHz). Animals were tagged with acoustic sensors(D-tags) that simultaneously measured movement in three dimensions.Whales reacted strongly to alert signals at received levels of 133-148dB SPL, mildly to conspecific signals, and not at all to ship sounds oractual vessels. The alert stimulus caused whales to immediately ceaseforaging behavior and swim rapidly to the surface. Although SEL valueswere not directly reported, based on received exposure durations,approximate received values were on the order of 160 dB re: 1 mPa\2\-s.(3) NMFS (2005) evaluated the acoustic exposures and coincidentbehavioral reactions of killer whales in the presence of tactical midfrequencysonar. In this case, none of the animals were directly fittedwith acoustic dosimeters. However, based on a Naval Research Laboratory(NRL) analysis that took advantage of the fact that calibratedmeasurements of the sonar signals were made in situ and using advancedmodeling to bound likely received exposures, estimates of receivedsonar signals by the killer whales were possible. Received SPL valuesranged from 121 to 175 dB re: 1 mPa. The most probable SEL values were169.1 to 187.4 dB re: 1 mPa\2\-s; worst-case estimates ranged from177.7 to 195.8 dB re: 1 mPa\2\-s. Researchers observing the animalsduring the course of sonar exposure reported unusual alterations inswimming, breathing, and diving behavior.For more detailed information regarding how marine mammals mayrespond to sound, see the Navy's IHA application, the Navy's associatedEA, Richardson's Marine Mammals and Noise (1995), or the referencescited on NMFS' Ocean Acoustic Program website (see ADDRESSES)