Australian Deputy PM criticises the ‘unsafe and unprofessional’ conduct of a Chinese warship ignoring warnings to stay clear of divers
Australian Defence Minister and Deputy Prime Minister, Richard Marles, said that he has raised ‘serious concerns’ with the Chinese government after members of a team of Royal Australian Navy Divers were injured by sonar pulses broadcast from a Chinese warship.
HMAS Toowoomba, an ANZAC-class frigate, was operating in international waters near Japan when its propellers became entangled in fishing nets. A team of divers was deployed to free the propeller when the ship was approached by the Chinese People’s Liberation Army Navy (PLA-N) destroyer DDG-139.
Toowoomba’s crew broadcast a warning to the Chinese vessel, which acknowledged the communication but continued its approach. Mr Marles said that the PLA-N destroyer was detected operating its hull-mounted sonar shortly afterwards, forcing the Australian divers to leave the water.
Mr Marles said the divers ‘sustained minor injuries likely due to being subjected to sonar pulses from the Chinese destroyer.’
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‘This is unsafe and unprofessional conduct,’ Marles wrote in a post on X. ‘The safety and wellbeing of our ADF personnel continues to be our utmost priority. Australia expects all countries, including China, to operate their militaries in a professional and safe manner.’
Can sonar be dangerous?
Sonar – sound navigation and ranging – was developed during the early 20th Century by the US Navy, and uses sound waves to measure distance and communicate underwater, as sound travels much further through water than electromagnetic radiation such as light, or the radio waves used by radar.
By broadcasting a sonic pulse underwater – known as ‘active’ sonar – and analysing the properties of the echo that is received, terrain, marine life, objects and other vessels can be detected. Many boats, from recreational craft to oil tankers use active sonar with little to no adverse effect, but military sonar is much stronger, transmitting at up to 230 decibels or more at the source.
Although it is not accurate to compare sound waves underwater with sound waves in air, to put some context around the number, the average rock concert is around 120dB. Sound, however, is a pressure wave, and underwater, the pressure wave generated by a 230+ decibel sonic blast would be – like the shock wave from an explosion – enough to kill a human being if they were close to the source of its transmission.
The pressure wave created by such a blast rapidly deteriorates to safe levels over quite a short distance from the source. Nevertheless, divers within a few hundred metres’ proximity to an active military sonar pulse may experience hearing loss, dizziness and disorientation.
While there is little research into the effects of sonar on humans, there have been studies into the effects of sonar on marine mammals. In 2002, The US Navy admitted that its high-intensity sonar system led to the deaths of several whales, and studies carried out since have found that certain species seem particularly sensitive to mid-range frequencies, resulting in disruption to their movements, depth of their dives and feeding behaviour.
If you want to know what sonar sounds like when you’re diving, take a look at this video of divers in the Bahamas being ‘pinged’ by a passing submarine.
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