Defence: Active Sonar

Senator Bartlett asked the Minister for Defence, upon notice, on 12 February 2002:

1. Is research into active sonar a research priority of the department.
2. (a) What is the decibel range of the low frequency active sonar (LFAS); and (b) in the marine environment, how far can that sound travel.
3. Have any active sonar tests been conducted by the Australian Navy; if so, where, when, and what permits were: (a) applied for; and (b) received.
4. If tests were conducted in the marine environment: (a) what impact assessment was undertaken; and (b) can those documents be provided.
5. What mitigation measures were imposed.
6. What information does the Navy have regarding the impacts of LFAS on marine mammals and other marine life.
7. (a) What distance/levels of exposure to underwater noise are considered safe for: (i) humans, (ii) different species of whales found in Australian waters, (iii) different species of dolphins found in Australian waters, (iv) dugong, (v) different species of seals found in Australian waters, (vi) fish, with particular reference to threatened species, (vii) different species of turtles, and (viii) different species of marine birds; and (b) can details of the scientific basis for these assessments be provided.
9. Is the Navy currently conducting any research into the impacts of LFAS on any species of marine life found in Australian waters; if so, can details be provided.
10. Why did the Navy recently withdraw an application for a test of LFAS in the Rottnest Trench.
11. Are any other tests planned; is so, can details be provided.

Senator Hill - The answer to the honourable senator's question is as follows:

1. Yes. Active sonar is the principal technology used by naval surface platforms worldwide to detect hostile underwater platforms and weapons (submarines, torpedoes, mines, etc.). Active sonars in the form of sonobuoys are also used by maritime fixed and rotary wing aircraft to detect and localise submarines. Warships are also usually fitted with underwater telephone, which emits active transmissions for voice communication with submerged submarines. Most ships also use high frequency active sonar in echo sounders used for navigation. Research into techniques for improving the ability of active sonar systems to detect underwater threats and so protect and preserve the ships and personnel of the Royal Australian Navy (RAN), and those put in its charge, is therefore a priority and necessity for the Department of Defence.
2. Low frequency active sonar (LFAS) is a generic term. It is generally used to identify a sonar system that emits sound at a frequency of 1 kilohertz (kHz) or less. The particular type of LFAS that has been linked in the media to environmental impacts on whales and dolphins is the Surveillance Towed Array Sensor System (SURTASS LFA sonar) used by the United States Navy (USN). SURTASS LFA is not a system used by the RAN and it has not been deployed in Australian waters.
   1. It is understood that the source level of SURTASS LFA is such that the intensity received by a whale, diver etc. at a distance of 10 meters from the source is approximately 215 decibels, relative to one micro Pascal (215 dB re 1 µPa). At a distance of 100 meters, the received sound intensity would be one one-hundredth, or 20 dB less, of the received sound intensity at 10 meters, i.e. 195 dB re 1 µPa. The received sound intensity will continue to decrease as distance to the source increases. To help place these numbers in context, it should be noted that common occurrences such as lightning strikes on the ocean produce received sound intensities approximately three hundred times this level (approximately 240 dB re 1 µPa at 10 meters) and sperm whales, in communicating, regularly produce total received sound intensities of 215 dB re 1 µPa at a distance of 10 metres.
   2. The distance any sound can travel (be detected) in the marine environment is highly variable and depends on numerous, changeable ocean characteristics such as salinity and temperature profiles. With respect to the impacts that arise from underwater sound propagation it is considered that the most relevant distance is that at which the received sound intensity is safe for the sensitive hearing possessed by marine mammals etc.
      
      
   For marine mammals (whales, dolphins, dugongs and seals), it is generally accepted by scientists that a received level of 178 dB re 1 µPa for intermittent or pulsed sounds is considered to be the best estimate of a safe exposure level. In the deep water in which the USN SURTASS LFA system would operate, a conservative estimate of the distance corresponding to this received sound level would be approximately one kilometre.
3. Yes. Testing mid-range frequency active sonar equipment onboard warships is a routine practice common to Navy's around the globe, to ensure correct system functioning and to train operators in the use of the system. The RAN has routinely tested equipment installed on its ships since the advent of sonar during World War II.
   
   Because testing mid-range frequency active sonar equipment is a routine practice, specific records of individual equipment tests are not kept in any consolidated form. Routine mitigating strategies are being put in place on RAN ships that ensure the use of sonar equipment does not have a significant impact on the environment. Where it is considered that the use of sonar has, will have or is likely to have, a significant impact on the environment, or where such operation might cause interference with a cetacean, then all relevant environmental approvals will be sought and obtained. To date there has been no requirement to seek such approval for the use of active sonar by Defence ships or aircraft.
4. 1. Impact assessments have been conducted into sources of underwater noise. These are:
      
      Environmental Impact Assessment of Underwater Acoustic Noise Trials, Timor Sea. PPK Environment & Infrastructure Pty Ltd. October 1998.
      
      Environmental Impact Assessment of Underwater Sonar Operations and Mitigation Procedures. PPK Environment & Infrastructure Pty Ltd. September 2000.
   2. Yes. In light of the continual worldwide development in understanding the impact of anthropogenic noise on marine creatures, the most recent of these assessments is under review. This updated report is likely to be released to the public when complete.
5. See response to Question 3.
6. The RAN does not use low frequency active sonar (LFAS) (that is, the USN SURTASS sonar), nor is any information held on its impacts on marine mammals and other marine life. Information on this equipment is available on the USN website at http://www.surtass-lfa-eis.com/.
7. As noted in question 2b, "safe distances" for exposure to underwater sound are highly dependent on the conditions prevailing in the marine environment. The most meaningful quantitative measure for assessing safety is the received sound intensity ("level of exposure").
   
   For marine mammals (whales, dolphins, dugongs and seals), a received level of 178 dB re 1 µPa for intermittent or pulsed sounds is considered by scientists to be the best estimate of a safe exposure level in general, although significantly higher levels might apply to some species, such as dolphins.
   
   For humans, a conservative estimate of the safe level is 150 dB re 1 µPa. A safe exposure level for fish is considered to be 170 dB re 1 µPa, and turtles 175 dB re 1 µPa. No information is available for marine birds, however, since their ears have developed for sound in air it is expected that safe levels would be higher than those of marine animals, because of their insensitivity to sound under water.
9. No.
10. No application to test LFAS (the USN SURTASS LFA) in the Rottnest Trench has been made. An application to test the medium frequency RAN Australian Surface Ship Towed Array Sonar System (ASSTASS) was made in December 2001 (EPBC Referral 2001/538) when trial assets became available at short notice. The RAN ASSTASS receives across a wide spectrum but has an active mode, which transmits at 1.5 kHz. A series of test sites, south of the Rottnest Trench were selected and mitigation procedures developed. It was intended to scientifically validate these proposed environmental mitigation procedures in conjunction with an independent Blue Whale Research Project Team from Curtin University. Internal Defence environmental consideration concluded that there was not sufficient certainty that the activity could be undertaken in a way that would not interfere with the Blue Whale population resident in the area at that time. The test therefore did not proceed.
11. The RAN has no planned tests for the USN SURTASS LFA. Further tests of the Australian ASSTASS system are intended; details of all Department of Defence active sonar tests covered by the EPBC Act (1999) will be publicly obtainable from the Environment Australia website. RAN ships will continue to test their mid-range frequency active sonars as operational circumstances dictate and consistent with newly implemented mitigation procedures.

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