They are the hulking giants of the sea, able to send their songs thousands of kilometres under the waves, but researchers still have little idea of how much whales can hear — and they are determined to find out.
Scientists from the University of Queensland have spent the past two whale migration seasons armed with a long pole, which they use to stick a small sucker-covered box to the side of humpbacks as they pass the coastline south of Noosa.
Associate Professor Rebecca Dunlop said it could be daunting reaching out a stick towards a creature weighing 30 tonnes.
"It can be confronting — that's a good way of putting it," Dr Dunlop said.
"You need to get extremely close, and you put a suction cup acoustic tag on using a long pole."
They're famed singers, but what can they hear?
The trackers sit on the side of the whale, while a second group of scientists dip a specially-designed speaker into the water, then watch to see how the whale reacts.
Without the tag, Dr Dunlop relies on a team of volunteers on a nearby hilltop watching and tracking the whale from afar, and updating the scientists on the water.
"The good thing about humpbacks is that they're migrating," she said.
"They tend to pick a direction and pick a speed, so you can quite accurately predict where they're going to end up six kilometres down the coast."
Each test is different, with sound frequencies ranging from between 62 hertz — akin to the deep rumble of an elephant — and 22 kilohertz, which is too high-pitched for humans to hear.
Is the ocean too noisy for our whales?
Dr Dunlop said scientists know that under-sea oil and gas drilling, naval sonar and other background noises are having some impact on whales.
"It's no new news that we're putting a lot of noise into the ocean," she said.
"We've got oil and gas industry with seismic surveys, we've got wind farm developments with pile driving and we've got shipping."
But they can't know how whales are being impacted until they know what they can and can't hear.
"That's the very piece that we're actually missing," Dr Dunlop said.
The research is paid for with $800,000 from the United States Navy's Living Marine Resources program, which funds studies into the under-sea environment to ensure it is not doing harm.
No music for the giant mammals … yet
Professor Michael Noad, also from the University of Queensland, is often on the boat that plays the sound in the whale study, known as the source vessel.
He said the sounds were played well ahead of the whale so that researchers could see how it responded once it came into range.
"Nine times out of 10, after they've worked out what the sounds are, often they just swim past the boat anyway," he said.
"They're almost curious as to what the sounds are."
He said the team played long tones of sound to the whales, rather than any chart-topping hits.
"We haven't played any music at them to see what they do to that," he said.
"They'd probably hesitate, wonder what on Earth it was, then just ignore it and swim straight past anyway."
The team will head out on the water for next year's whale migration, before publishing its findings.
