Sounds from the depths of the ocean
Dr Doug Cato has been studying the sounds of the sea and is assisting the navy to minimize their impact on marine mammals.PT2M34S http://www.canberratimes.com.au/action/externalEmbeddedPlayer?id=d-2aqut 620 349 December 3, 2012
BOTH are big and slow, but warships and whales are best kept far apart.
The din of aircraft carriers, submarines and destroyers rumbling through the water has been known to lead some reclusive pods of whales to beach themselves, while their cries may drown out the navy's sensitive sonar equipment.
That's where Doug Cato comes in. The adjunct professor from the Defence Science and Technology Organisation received the 2012 Minister's Award for achievement in defence science on Tuesday for a career spent listening to the sounds of the sea.
Before each naval exercise sailors use a computer to check their ''Cato Curves''. This is an equation considering factors such as wind speed, nearby marine life, rain and the drone of distant ships to predict the background noise faced by sonar operators.
The calls of the humpback whale can be heard tens of kilometres away and from a distance Dr Cato said the nattering teeth of ''fish choruses'' sound a mighty roar.
But for the sonar operators these are red herrings. They are listening instead for propellers, periscope movement and the ominous sound of a torpedo door opening.
''Obviously that's not good to hear unless it is your own boat,'' said Chief Petty Officer Robert Pringle, chief instructor of anti-submarine warfare at the School of Maritime Warfare in Sydney.
He said although Cato Curves are no longer plotted manually, they remain essential to navy operations. ''Back in my day you would get the paper graph out and see the effect of biological noise on your sonar,'' he said. ''It's now integrated into a computer system but it still provides the answer based on some of the research Doug has done.''
Yet for all our modern tools, Dr Cato said marine life still has the superior technology. ''Their sonar is better than ours,'' he said. ''That's why the US Navy uses dolphins to find mines in much the same way they use sniffer dogs.''
Dr Cato, 71, joined the Royal Australian Navy Research Laboratory in the 1960s, fresh from a degree in geophysics, and said he became fascinated by the beauty and complexity of ocean sounds.
''When you hear the humpback whale song you wonder why an animal would be producing something as spectacular as that,'' he said.
The song, about 10 minutes long, is used to attract a mate and is a series of phrases and themes delivered in order. On the east coast every whale sings from the same song sheet with only minor variations, while off the west coast of Australia and across the Pacific the song is different.
Dr Cato said though he marvels at the aquatic soundscape, where noise travels better than it does through air, he remains ''a dispassionate scientist who is trying to understand what's going on''.
He recalled that humans are still yet to attribute every sound from the deep. ''It's very difficult. You hear a sound but the source might be quite a distance away. You might see a whale close by, but it might not be the one. There still remain some mysteries.''