SURTASS LFASurveillance Towed Array Sensor System Low Frequency Active
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Activists and the Navy disagree as to the subjective intensity of the sound generated by SURTASS LFA. On paper, the numbers are apparently unambiguous.
Acoustic scientists disagree as to what level of sound in air would be the equivalent of a 140 dB pulse from a SURTASS LFA array 300 nautical miles away, but most generally subtract 26 dB from underwater sound intensities to find equivalently loud sounds in air at sea level.
[A] 60 dB difference represents a million-fold power difference; so, [sic] it can easily be seen how misleading it can be to try to compare underwater sound that a system like SURTASS LFA sonar makes with in-air sound that a jumbo jet makes.
Ironically, the best existing set of safety standards for exposure to low-frequency sonar comes from the same institution planning to contravene those standards with SURTASS LFA: the US Navy.
Other SURTASS LFA tests have done damage to whales.
They decry the fact that the Navy's Draft OEIS/EIS claims SURTASS LFA poses no overwhelming threat to cetaceans or other wildlife, despite the fact that the Navy's tests included no long-term monitoring of animals in the test areas.
SURTASS LFA's planned operating intensity, as noted before, is 230 dB: ten million times more intense than 160 dB.
The Navy has responded to concerns about SURTASS LFA's potential for devastation of marine life by agreeing to a couple of mitigations, including attempts to monitor for the presence of marine mammals by high-frequency sonar and shutting down the system in their presence, a proposition of dubious likelihood during hostilities.
Looking at these assurances, and at the map in the OEIS/EIS of SURTASS LFA Sonar Potential Operating Areas (see graphic), one could logically reach the conclusion that SURTASS LFA is intended for use in the open ocean, much as SOSUS was used to detect the Soviet submarines of a generation ago.
Of the many references to SURTASS LFA in defense trade publications throughout the 1990s, none -- zero -- have mentioned a use other than protecting US Navy ships as they enter the littoral waters of hostile foreign nations.
It is possible that the US Navy, out of a deep and abiding respect for marine life and the sanctity of its promises, will refrain from ever using SURTASS LFA in such vulnerable areas.