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

COMPTUEX/JTFEX EA/OEA Final Chapter 4actual impulse value corresponding to the 31-psi-ms index is a complicated calculation. The acousticthreshold is derived from:Again, to be conservative, CHURCHILL used the mass of a calf dolphin (at 12.2 kg), so that the thresholdindex is 30.5 psi-ms.4.3.1.7.18 Criteria and Thresholds: InjuryNon-lethal injurious impacts are defined as eardrum rupture (i.e., tympanic-membrane (TM) rupture) andthe onset of slight lung injury. These are considered indicative of the onset of injury. The threshold forTM rupture corresponds to a 50 percent rate of rupture (i.e., 50 percent of animals exposed to the level areexpected to suffer TM rupture); this is stated in terms of an EFD value of 1.17 in-lb/in 2 , which is about205 dB re 1 Pa 2 -s. This recognizes that TM rupture is not necessarily a life-threatening injury, but is auseful index of possible injury that is well-correlated with measures of permanent hearing impairment(e.g., Ketten (1998) indicates a 30 percent incidence of permanent threshold shift (PTS) at the samethreshold).4.3.1.7.19 Criteria and Thresholds: Non-Injurious ImpactsThe CHURCHILL criteria for non-injurious harassment are temporary (auditory) threshold shift (TTS), aslight, recoverable loss of hearing sensitivity (U.S. Navy, 2001). The criterion for TTS used in thisdocument is 182 dB re 1 Pa 2 -s maximum EFD level in any 1/3-octave band at frequencies above 100 Hzfor toothed whales (e.g., dolphins). A 1/3-octave band above 10 Hz is used for impact assessments onbaleen whales.In Finneran et al. (2002), a watergun was substituted for the ES because it is capable of producingimpulses with higher peak pressures and total energy fluxes than the pressure waveforms produced usingthe ES. It was also preferable to other seismic sources because its impulses contain more energy at higherfrequencies, where odontocete hearing thresholds are relatively low (i.e., more sensitive). Hearingthresholds were measured at 0.4, 4 and 30 kHz. MTTSs of 7 and 6 dB were observed in the beluga at 0.4and 30 kHz, respectively, approximately 2 minutes following exposure to single impulses with peakpressures of 160 kPa (23 psi), pk-pk pressures of 226 dB re 1 Pa, and total EFD of 186 dB re 1 Pa 2 -s.Thresholds returned to within 2 dB of the pre-exposure value approximately 4 minutes post exposure. NoMTTS was observed in the single bottlenose dolphin tested at the highest exposure conditions: peakpressure of 207 kPa (30 psi), 228 dB re 1 Pa pk-pk pressure, and 188 dB re 1 Pa 2 -s total energy flux.NMFS determined in their 2005 Precision Strike Weapon IHA permit that the pressure criterion forexplosions can be amended from 12 psi to 23 psi. It was further noted in the 2005 IHA permit that settingthe pressure metric of the dual explosive criteria at 23 psi is conservative, while setting the pressuremetric at a higher level has not been scientifically validated at this time (NMFS, 2005).Due to an operational re-assessment of the Improved Extended Echo Ranging (IEER) sonobuoy, the Navyhas determined that EER/IEER sonobuoy will not be deployed during Jan 07 – Dec 07 major rangeactivities. Consequently, acoustic exposures associated with IEER have been omitted from underwaterexplosive calculation results. However, EER/IEER may be included in ASW Operations after December2007. Should EER/IEER be introduced into major range events after December 2007, the analysis ofpotential EER/IEER use in the EA/OEA can be used as the basis of regulatory consultation.Models of pressure propagation from underwater explosives predict the distances at which marinemammals may experience acoustic effects, and thus, are important in anticipating and mitigating potentialeffects. Exclusion distances depicted in Underwater Detonation mitigation distances (Chapter 5)4-49 February 2007