Whales struggle to hear each other. Guess whose fault that is

New research into how baleen whales make low, vibrating sounds is also highlighting the serious dangers these animals face from ocean noise pollution.

These bristle-mouthed animals include some of the world's most recognizable species, including the blue, humpback and bowhead whales, among others. 

"They make sounds of very low frequencies very close to the surface," said Coen Elemans, study author and professor of bioacoustics at the University of Southern Denmark. 

"And that's exactly where we make boating noise, in exactly the same frequency range and also on the surface." 

Compared to their toothed cousins like orcas or belugas, baleen whales use a novel method to make these rumbling baritones, essentially taking their vocal organs and rotating them to vibrate against an inner "cushion," researchers say.  

"It makes a Harley-Davidson sound like a child's toy," said Tecumseh Fitch, co-author and cognitive biology professor at the University of Vienna. 

The study, published in the journal Nature, focuses on low-frequency sounds made by these animals — around the 10 to 30 hertz range. Researchers suggest those sounds can't be made for prolonged periods of time in deeper parts of the ocean because of the whales' physiology. Farther down, the air is just too compressed to use their vocal organs effectively.

"In other words, they can't escape the surface noise created by ships, by human noise, by going way down," Fitch told CBC News from Sanibel Island, Fla. 

"It'd be like if you're in a very crowded bar and you need to sing to find your mate and everybody else is making all this noise." 

Beyond mating, it's long been known that ship noise impacts whales — both baleen and toothed — and their ability to orient themselves, locate prey and avoid dangers. 

"These animals perceive danger by hearing," said Hussein Alidina, lead specialist for marine conservation with WWF Canada. "So if that aspect is getting masked or interfered with, then it poses a danger to them." 

His organization recently called out delays to the federal government's Ocean Noise Strategy, which was supposed to come out in 2021 but has yet to be drafted. Alidina's hope is that a comprehensive strategy will co-ordinate what he refers to as a "fairly piecemeal and geographically separated" current approach to underwater noise. 

Alidina says it's important the paper highlights the limitation of whales' bodies to make these sounds.

But just how researchers figured that out involved what Fitch describes as the "ugly business" of whale research: cutting out vocal organs of dead whales.