Some years ago, Michel Andre found himself staring at the body of a dead sperm whale on a beach in the Canary Islands. It was obvious that the animal had collided with a ship – but why? Only later, after methodically surveying the whales which lived in the area and measuring the increase of sound pollution from ships did it become clear that there was a link.
There’s a world of sound and animal communication never observed with such clarity before
The whales had become desensitised to the noise of approaching boats and were being struck by them, often fatally. “We never thought that this could be something that could kill,” recalls Andre, who is the director of the Laboratory of Applied Bioacoustics at the Technical University of Catalonia, Barcelona.
Andre has spent 20 years developing an advanced system for listening to subsea noise in order to better understand why incidents like this happen. His underwater microphones, or hydrophones, have exposed a world of sound and animal communication never observed with such clarity before.
Watch Andre collecting and decoding the sounds in the video below:
The elaborate listening apparatus developed by Andre for detecting sound in the ocean is dubbed “smart ears”. It not only detects the voices of whales, dolphins and other creatures, but also the deafening whirr of boats, propellers and other marine machinery.
It was not an easy task. Sound waves don’t travel through water in the uniform, predictable way they do through the air. Instead, the temperature, salinity and flow of the water column – among other things – dramatically impact their path.
There’s a lot of distortion, so Andre and his team had to develop algorithms that could analyse the sounds in real-time and match them to a database of known ocean noises: everything from whale song to dolphin-speak. No two sounds are the same, but the algorithms are clever enough to pick out similarities in the audio waves and match them with a reasonable degree of accuracy.
Andre’s system can also estimate how far away the sound source is by interpreting how distorted the sound itself has become – partly an indicator of how much water it has travelled through before reaching the hydrophone. The quality of sound, of course, is also dependent on the movement of the animal that made it. “If the animal turns its head you will not get the same sound or the same intensity,” he says.
After taking tissue samples from the ears of beached whales, evidence of harm was found in the cells of those sensory organs
A range of hydrophones, on buoys monitored by Andre, is now picking up audio signals in seas all around the world. And the computer analysis is done extremely quickly – according to Andre there’s just a three-second delay between picking up the sound and predicting algorithmically what it is. Then, the result is transmitted back to the shore.
“We are overloaded with information,” he says. “It’s 24/7 – data coming from over 100 channels around the world.”
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Andre’s team aren’t just listening – they have also studied the physiological damage caused to animals by noise. After taking tissue samples from the ears of beached whales, evidence of harm was found in the cells of those sensory organs. This, then, was why creatures had lost their ability to detect the noise of ships.
“If there are some missing structures of these cells, it means that the animal cannot codify any more the sound that corresponds to this specific cell,” he explains.
The kind of noise that whales and other marine animals have to contend with is not trivial, ranging from ship sounds to loud explosions.
Christopher Willes Clark, a bioacoustician at Cornell University (who is not involved with Andre’s work), says ships easily drown out the noise of whale songs and the animals are also exposed to deafening explosions caused by subsea oil and gas exploration surveys.
“We set off extremely loud explosions every 10 seconds for months at a time such that I can hear a prospecting survey going on near Ireland – I can hear that off Virginia,” says Clark.
One solution is to divert shipping routes to courses where ships are statistically less likely to encounter marine mammals
What can be done? One solution is to divert shipping routes to courses where ships are statistically less likely to encounter marine mammals. It’s also possible, sometimes, to slow down to 10 knots an hour (18km/h) or less, which is less likely to fatally injure a whale. Clark explains that this leads to a “significant” reduction in the chances of an animal collision.
As for tackling the root cause of the problem, the UN’s International Maritime Organisation (IMO) has already published guidelines on how to quieten ships, but it will be a while before the impact of such changes might be observed in the wild. Plus, businesses and vessel operators will have to co-operate.
“The ocean is not our world,” comments Andre. But it is ours to look after. And thanks to his work, we can better understand the impact of subsea sound pollution.
“The fact that now we have access to the sound, it is completing the picture that we have,” he says. “This is the only way we can understand what is going on.”
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