A failed attempt to use sound to help track the currents and movements of ice sheets in Lake Superior has turned into a new type of audio study for a researcher who studies the large lake.
"We had this experiment and we had some issues with data corruption because there's all this natural sound ... in Lake Superior," said Jay Austin, a professor at the Large Lakes Observatory, at the University of Minnesota Duluth.
"It got me thinking about ... what is the acoustic environment of the lake?"
Using a hydrophone — basically an underwater microphone — to record sound below the lake's surface, Austin said he was able to do similar work that oceanographers have been doing for decades in the world's oceans, namely mapping the underwater soundscape.
"There are good reasons for that," he said of why underwater sonic studies are carried out in the ocean. "Largely tied up with submarine warfare and understanding that defence environment."
"There's no such threat in lakes and so they've sort of gone unnoticed."
'The song of the lake'
Two of the sounds detected below the lake surface were wind, and the rumble of passing ships. But the tape also picked up a number of unexpected clicking or light thumping sounds.
"The song of the lake," Austin said, chuckling.
Existing research suggests they could be caused by burbot — a form of freshwater cod, he said.
"It's not clear to me that the noises they're making are actually communication," he said. "The clicks are sort of boring, to be perfectly blunt, and I don't think that they can encode a lot of information in that."
Rather, Austin figured the sounds could be made by a part of the fish's anatomy while they're swimming.
One oddity the researchers noted, however, was that the fish appeared to stop making the sound when ships were passing by. It wasn't a case of the sound of the vessels drowning the clicks out either, Austin said, as they would be loud enough to be heard over the din.
"I'm looking forward to starting to work with biologists to understand a little more about what these clicks might suggest," he said.
As for what application this could have, Austin pointed to taking stock of fish populations.
"Making measurements of fish abundance is a very difficult thing: you have to go out with boats and nets," he said.
"If there were ways that we could use sound to monitor fish abundance ... there might be a way to make those abundance measurements much more efficiently."
The sound of the wind underwater might also be useful for tracking wind speed, he said, especially in the winter, when ice cover prevents researchers from placing buoys on the water to record that information.
The applications of the sounds may also go beyond science. Austin said experimental musicians have also expressed interest in using the Lake Superior sounds.