How the invisible powers of sound shape our lives and world

When a baby cries, it’s doing what babies do: wailing to be fed, burped, changed or out of fear of being alone. But there’s another message embedded deeply within the whining — something hardwired and unseen — that jerks parents awake at night to rush to the crib.

There are endless sounds competing for our attention, so why is it that a cry cuts through and demands we not only listen, but do something about it?

CBC Radio’s Hidden Frequencies explores the sounds around us — from the unheard and unnoticed to the absent or loud.

Whether it’s a bird call, an explosion or a baby’s cry, the show delves into how these sounds can help us learn more about ourselves as humans, our impact on the environment and even how to better care for kids.

What’s in a cry?

For ages, scientists have understood that the distressing cries of babies produce the love and stress hormones oxytocin and cortisol in caregivers, and that powerful cocktail helps jolt them into action.

Susan Lingle wasn’t expecting to put that knowledge to the test, but it crept into her animal behaviour and ecology research on the windswept prairie about two decades ago.

Evolutionary biologist Susan Lingle scans the windswept Alberta field site where she studied predator-prey interactions between coyotes and deer. That led her back into the lab in Winnipeg to see if some of the same processes she observed on the prairie held true in human parents of newborns. (Submitted by Susan Lingle)

The University of Winnipeg associate professor was spying on the closely-related mule deer and white-tailed deer and the coyotes that hunt them in southern Alberta when she noticed the deer behaved differently when attacked.

Mule deer appeared to be more bold and would band together and fight back. Meanwhile, white-tailed deer would disperse and flee.

While studying these predator-prey interactions, Lingle also noticed mule deer would sometimes help orphaned white-tailed fawns crying out in distress.

“It’s kind of weird because in evolutionary biology we think something has to be in it for the animal … to be able to pass on its genes,” she said. “I haven’t heard of any other cases in which an animal from one species will defend an animal from another species against a predator.” 

An adult mule deer and its fawn forage in a southern Alberta grassland. Mule deer will rush in to protect orphaned and distressed white-tailed deer fawns, but the adult white-tailed deer don’t seem as interested in returning the favour. (Submitted by Susan Lingle)

Curiously, this only went one way: the flighty white-tailed deer weren’t tending to baby mule deers left in similar situations, Lingle said.

Mule deer babies cry in a higher pitch than white-tailed deer, which gave her a wild idea.

Lingle’s research team toyed with the pitch of recorded mule deer cries, lowering it to the same range as white-tailed deer. They also did this with the cries of fur seals, bats, kittens and even human babies to test the limits of their hypothesis.

CBC Radio Specials2:31The trick of pitch: toying with evolutionary wiring in deer

Susan Lingle, an animal behaviour, ecology and evolution expert at the University of Winnipeg, explains how a wild idea led her to uncover some hard-wired biological processes in deer — and sparked questions of how similar they may be in humans. 2:31

When they went back out on the prairie and played the altered cries, the altered recordings managed to pull the white-tailed deer in — no matter the species — as if they were bounding to the rescue of one of their own.

This hinted that basic human responses could be shared with other animals, Lingle said.

“I think a lot of work in animal behaviour … has highlighted many sources of commonality and certainly that has an affect on the way we treat animals, whether it’s for livestock or other purposes,” she said. 

Something fishy about dynamite rules

Vince Palace is another researcher whose curiosity led him to look into animals — specifically, how the ripple effect of underwater explosions harm fish.

Palace is the head research scientist at the Experimental Lakes Area (ELA), a cluster of fresh water basins nestled in the boreal forests of northwestern Ontario.

Vince Palace is head research scientist at the Experimental Lakes Area in northwestern Ontario. (Bryce Hoye/CBC)

Scientists at the ELA have been doing whole-ecosystem freshwater research for half a century, including one unconventional study that started with a bang.

Researchers wanted to know what impact the hunt for oil and other natural resources was having on fish. 

Seismic exploration, the industry practice of detonating charges beneath the ice, is used in northern lakes that don’t freeze to the bottom. The detonation sends shock waves into the Earth at the lake bottoms, Palace said, allowing geologists to assess whether there are oil or gas reserves below.

CBC Radio Specials1:08How underwater detonations by industry served a serious kick in the guts for fish

Vince Palace, head research scientist at the Experimental Lakes Area, explains how the hunt for gas and oil beneath lake bottoms in the north was harming fishing. 1:08

To replicate those shock waves, Palace’s team drilled big holes through lake ice, then put fish in cages and lowered them into the cold water. In a different ice hole a ways away, they set off dynamite charges underwater. The force of the distant detonations was in line with what industry standards at the time suggested was safe for aquatic life to withstand. 

Afterwards, they euthanized the fish and opened them up. Autopsy results showed pressure from the blast resulted in internal bleeding and organ damage. The findings quickly led to policy changes that halved the force allowed for this kind of seismic exploration. 

“I’m more driven to see what application does the science have and how will this better our world or better our management of natural systems, if in fact we are managing them,” said Palace. “It was really cool to see your science impact policy immediately and so profoundly.”

Using AI to listen to birds

Elly Knight is another researcher hoping to see her science make an impact — not in the water, but in the sky. 

The University of Alberta graduate student studies common nighthawks. Despite what the name suggests, the species is at-risk in Canada.

The boomerang-shaped birds can be elusive, and that’s made tracking them and understanding how vulnerable they are a real challenge.

Knight and her colleagues placed hundreds of bioacoustic recorders in wetlands and forests near Fort McMurray, Alta., to capture sounds of the wild. Her research took place between 2015 and 2019.

Elly Knight holds a common nighthawk captured in the darkness at one of her field sites in Alberta. (Submitted by Elly Knight)

The challenge became sifting through it all to find the nighthawks.

“I think we’ve got something like two to three hundred terabytes of acoustic data at this point,” said Knight. “It would take you between one and two lifetimes to listen to all of that.”

CBC Radio Specials1:15‘The cocktail party problem’: Challenges training AI to identify individual species amid cacophony of nature sounds

Elly Knight explains how artificial intelligence has enabled her lab to pore over lifetimes worth of bird sound data in a jiffy — and some of the limitations the technology faces. 1:15

Knight’s solution: voice recognition artificial intelligence programmed to pore over all that data and flag the signature “peent,” “beerb,” and “vroom” sounds of the nighthawk. The resulting analysis will help shed light on the darkness-loving nighthawk’s population numbers and how it’s faring.

Cries predict development

Like Susan Lingle, Stephen Sheinkopf’s research dives deep into baby cries.

Sheinkopf is an associate professor of psychiatry and pediatrics at the Brown Center for the Study of Children at Risk in Rhode Island.

He’s spent his entire career looking for early signs of autism in infancy, and suggests how high or low a baby’s cries sound could be a clue. 

“Children who have a family history of autism and then subsequently develop autism produced cries that were higher in pitch,” Sheinkopf said of one of his older studies.

CBC Radio Specials2:27What the ‘fundamental frequency’ of baby cries tells us about autism

Stephen Sheinkopf’s research on cries in infants suggests there are signs in a cry that hint at the likelihood of whether a baby will go on to develop autism later on. 2:27

He is also looking at what the timing and resonance — how the vocal chords vibrate — of the cries could tell us about the minds of these infants.

Adults may also perceive the cries of babies who later develop autism differently. 

Sheinkopf invited parents to his lab to listen to cries and fill out a survey about how typical, distressed and painful they perceived the cries to be.

“The ratings resulted in a description of the autistic cries as sounding less typical, as sounding to the parents [as] more in distress, as sounding to the parents who rated them as being more in pain,” he said. 

“What might be the result if a parent was experiencing that for their own child? Might that impact how they are responding to their child in terms of their caregiving strategies?” he said.

His research didn’t dig into those questions, but Sheinkopf hopes his work could one day help identify children who may need extra monitoring. 

“That might be the long-term impact of this work, but we have some steps to go through before we get there,” Sheinkopf said. 


Written by Bryce Hoye. Hidden Frequencies was produced by Bryce Hoye, Danelle Cloutier and Molly Segal.

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