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

COMPTUEX/JTFEX EA/OEA Final Chapter 4μPa 2 -s as a reference point to derive a TTS threshold in terms of EL. A second TTS threshold, based onpeak pressure, was also used. If either threshold was exceeded, effect was assumed.The 192 dB re 1 μPa 2 -s reference point differs from the threshold of 195 dB re 1 μPa 2 -s used in theSCIRC Draft EIS/OEIS. The 192 dB re 1 μPa 2 -s value was based on the minimum observed by Ridgwayet al. (1997) and Schlundt et al. (2000) during TTS measurements with bottlenose dolphins exposed to 1-second tones. At the time, no impulsive test data for marine mammals were available and the 1-secondtonal data were considered to be the best available. The minimum value of the observed range of 192 to201 dB re 1 μPa 2 -s was used to protect against misinterpretation of the sparse data set available. The 192dB re 1 μPa 2 -s value was reduced to 182 dB re 1 μPa 2 -s to accommodate the potential effects of pressurepeaks in impulsive waveforms.The additional data now available for onset-TTS in small cetaceans confirm the original range of valuesand increase confidence in it (Finneran et al., 2001, 2003a; Nachtigall et al., 2003a, 2003b). The SCIRCDraft EIS/OEIS, therefore, uses the more complete data available and the mean value of the entireSchlundt et al. (2000) data set (195 dB re 1 μPa 2 -s), instead of the minimum of 192 dB re 1 μPa 2 -s. Fromthe standpoint of statistical sampling and prediction theory, the mean is the most appropriate predictor –the “best unbiased estimator” – of the EL at which onset-TTS should occur; predicting the number oftakes in future actions relies (in part) on using the EL at which onset-TTS will most likely occur. Whenthat EL is applied over many pings in each of many sonar operations, that value will provide the mostaccurate prediction of the actual number of takes by onset-TTS over all of those operations. Use of theminimum value would overestimate total harassment numbers because many animals counted would nothave experienced onset-TTS. Further, there is no logical limiting minimum value of the distribution thatwould be obtained from continued successive testing. Continued testing and use of the minimum wouldproduce more and more erroneous estimates.4.3.1.7.8 Criteria and Thresholds for Behavioral EffectsThis section presents the effect criterion and threshold for behavioral effects of sound leading tobehavioral disturbance without accompanying physiological effects. Since TTS is used as the biologicalindicator for a physiological effect leading to behavioral disturbance, the behavioral effects discussed inthis subchapter may be thought of as behavioral disturbance occurring at exposure levels below thosecausing TTS.A large body of research on terrestrial animal and human response to airborne noise exists, but resultsfrom those studies are not readily extendible to the development of effect criteria and thresholds formarine mammals. For example, “annoyance” is one of several criteria used to define impact to humansfrom exposure to industrial noise sources. Comparable criteria cannot be developed for marine mammalsbecause there is no acceptable method for determining whether a non-verbal animal is annoyed. Further,differences in hearing thresholds, dynamic range of the ear, and the typical exposure patterns of interest(e.g., human data tend to focus on 8-hour-long exposures) make extrapolation of human noise exposurestandards inappropriate.Behavioral observations of marine mammals exposed to anthropogenic sound sources exist; however,there are few observations and no controlled measurements of behavioral disruption of cetaceans causedby sound sources with frequencies, waveforms, durations, and repetition rates comparable to thoseemployed by the tactical sonars to be used during COMPTUEX/JTFEX. At the present time there is noconsensus on how to account for behavioral effects on marine mammals exposed to continuous-typesounds (National Research Council, 2003).4-31 February 2007