Season 5: Episode 14

Disquieting

Humans have filled the world with so much noise that the only sounds many of us often hear on a daily basis are our own. But all this sound isn’t great for our planet mates, and it isn’t great for us either. In this episode, we look at how human-made sound makes it hard for other creatures to listen and communicate.

Guests

AntoInE Perez Muñoz

Antoine Perez Muñoz is an expert in public and environmental health in Paris.

Christine Erbe

Christine is a John Curtin Distinguished Professor in the School of Earth and Planetary Science at Curtin University and the Director of the Centre for Marine Science and Technology. She is also a Fellow of the Acoustical Society of America, and former Chair of the international conference series on The Effects of Noise on Aquatic Life.

Mette Sørensen

Mette Sørensen is a senior scientist at the Danish Cancer Society,

Valeria Vergara

Dr. Valeria Vergara is co-director of the  Cetacean Conservation Research Program at Raincoast Conservation Foundation. She researches acoustic communication in whales and dolphins, and the effects of noise on these sound-centered species. Her work has shown how beluga calves develop their vocal repertoire, and how noise impacts the contact calls they use to stay connected with their mothers. She has also shown that belugas can exploit ultrasonic signals to maintain communication in noisy environments, and is now co-leading a study that uses drones, hydrophones, and AI to decode killer whale communication dynamics.

Credits

Transcript

[00:00] INTRODUCTION

NOISY MONTAGE SLOWLY BUILDING

AMY: Have you ever been out at a restaurant or a concert, when someone nearby starts to get really really loud…totally disrupting everyone around them…completely clueless about how much their noise is intruding on your experience?

AMY: Well, that’s us. That’s what our species is doing to the rest of life on Earth.

NOISE CREST

AMY: Some of our noise emanates from particular places—factories, construction sites, our own backyards. But it also comes from our movements between places; shipping ourselves and our stuff here and there, day and night. Transportation noise is increasingly relentless and hard to escape, but the birds and frogs and other animals we’re bothering—they can’t tap us on the shoulder and ask us to pipe down. That’s up to us. So I’m going to re-ask a question I posed in the first episode for this season: how many sounds do you hear in a day that are not made by people?

AMY: How many voices of other creatures? How often is it quiet enough for you to hear the wind through the trees, or the sound of falling rain, or whatever the sounds of the more-than-human world may be where you live? What are those sounds? Do you know? Is it possible for you to know?

AMY: After hundreds of thousands of years of attentive listening to our places and all the lives in them, many of us now spend our days with the sounds of just one very loud hominin in our ears. It’s become so normal to us that we don't even think about it. But it's actually a massive change in the use of our acoustic attention. What is it doing to us, to live inside these walls of our own noise? And what is it doing to our planet mates?

AMY: Welcome to Threshold, I'm Amy Martin, and there’s no point in trying to sugarcoat it: the answers to the questions are kind of heavy. But one thing that makes it more possible for me to face the impacts of our noise is when I zoom out and think about how weird this moment in time is. We’re the only species that’s ever filled the world with so much noise, and we haven’t actually been doing it for that long. There’s no rule that says we inevitably have to keep getting noisier and noisier. It’s entirely possible for us to change. And if we want to share the planet with other beings in the future, and keep ourselves healthy, I think we have to.

THEME MUSIC

[03:19] A SEGMENT

AMY: So I want to start by inviting you to step out of a human frame of reference for a minute. Or, swim out of it maybe. Let's say you're an otter on a remote Alaskan island. Look at you, you're adorable. 

GLACIER ICE ON BEACH

AMY: You're out searching for food under the midnight sun, and you pause at the water's edge, listening. What does the world sound like to you?

GLACIER ICE ON BEACH

AMY: There's no wind, the water is still. On land, the only thing you can hear is the trickling sounds of melting ice.

HUMPBACK WHALE TRUMPET

AMY: When suddenly a humpback whale surfaces, and sends a call echoing across the water.

HARBOR SEAL

AMY: Then a harbor seal lets out a little bark, beckoning.

And...you dive into the icy water, protected by your thick pelt. And here under the surface, you're immersed in the voices of your cold-water companions.

Orcas.

ORCAS

AMY: Mighty sperm whales sending out their powerful clicks.

SPERM WHALES

AMY: Narwhals, the unicorns of the sea, whistling, singing, buzzing.

NARWHALS

AMY: You hear a bearded seal.

BEARDED SEAL

AMY: Bowhead whales.

BOWHEAD WHALE

AMY: Humpback whales.

HUMPBACK WHALE

AMY: And the seemingly perpetually smiling, milky white belugas.

BELUGAS

VALERIA: They are an incredibly sociable whale.

AMY: Valeria Vergara studies communication in marine mammals with the Raincoast Conservation Foundation, based in British Columbia, Canada.

VALERIA: A lot of whales and dolphins are very social. But belugas, man, they form long, long term friendships, not just with relatives, but with non relatives as well. And these friendships left a lifetime. A lifetime in beluga society is the same as a lifetime in humans. They can live 70, 80, 90 years.

AMY: Belugas and other whales are mammals whose ancestors started out on land and then moved into the sea. Their migration into the ocean started around 50 million years ago, with a wolf-like animal. Over time, legs transformed into flippers, noses became blowholes, and a diverse group of whales, dolphins, and porpoises evolved, which we call cetaceans. Some of them traded teeth for comb-like structures in their enormous mouths to strain out krill and other food from the water. These are the baleen whales—like humpbacks, minkes, fins, bowheads, and the largest animals ever known to have existed on earth, blue whales. 

BLUE WHALE

AMY: This call has been sped way up to make it audible to us. Blue whales make sounds so low, we usually can’t hear them.

AMY: Other cetaceans kept their teeth – dolphins, porpoises, sperm whales, and belugas. But all cetaceans use sound to communicate. And Valeria says belugas are especially chatty. Some people refer to them as sea canaries.

VALERIA: Whalers used to hear their sounds from the hull of their boats. And they they really do sound like a canary, sort of like you're immersed in a jungle of birds.

BELUGAS

VALERIA: It's probably no exaggeration to say it's one of the most communicative mammals along with humans.

BELUGAS

AMY: Belugas depend on sound because they depend on each other.

VALERIA: So if you think about the need for a social species to communicate, you know, this is a very they have a very complex sociality. They need to somehow maintain those social bonds.

AMY: And they need to maintain them underwater, where light doesn't penetrate very far. If there's any light at all.

VALERIA: Beluga whales live in the Arctic for most of their of their lives. And the Arctic is dark for six months of the year or more. The sun doesn't come out, so the water is completely dark and they don't have the visual senses to stay in touch with one another, to stay near their loved ones, to maintain those very important social bonds. They have to do it through sound.

AMY: One of the most important sounds in the beluga repertoire is what's known as a contact call. It’s especially crucial for mothers and calves.

VALERIA: An adult contact call sounds like a creaky, rusty door, married a chainsaw and produced a hybrid. You know? (laughs)

AMY: (laughter) Sounds lovely.

VALERIA: Yeah, it's it's not an appealing sound at all. It's like, it's just this very loud, very piercing, very broadband pulsed call.

ADULT CONTACT CALL

AMY: This is essentially beluga-speak for: where are you? Stay close to me!

VALERIA: And a calf replies with the equivalent of a sound that's like running your fingers through a comb. It's very soft.

CALF REPLY

AMY: And this is the baby saying, here I am, Mom. Here I am. Right here. It's just one type of beluga call in a vast library of sounds that these animals use to stay in touch with each other in these cold, dark waters.

VALERIA: All species of whales use sound for nearly all aspects of their lives. But this is particularly so for for belugas. They use sound to communicate to, to maintain contact, to navigate through those ice lids in the Arctic, to detect their prey, to avoid predators. All of that important stuff.

AMY: And it's worked well for them. For millions of years, sound has been a crucial, reliable tool. But over the last hundred years or so, it's gotten harder and harder for belugas and other whales to hear each other.

UNDERWATER NOISE (DISTANT)

VALERIA: Sound travels very, very well in water. This means that noise travels very well in water.

AMY: Sound waves travel more than four times faster in water than they do in air, and they can stay loud for a much longer time.

UNDERWATER NOISE

VALERIA: When we hear a noisy boat or a vessel or a cargo ship above water, we can hear its engine, you know, but it's not deafening to a whale the sound can be deafening.

UNDERWATER NOISE

AMY: These are real-world recordings of big ships, small boats, tidal turbines, seismic air guns, and other human-made underwater noises.

VALERIA: And the levels of underwater human generated noise have been increasing at a really staggering rate over the last, I would say, 40, 50 years. And it's not just ships and recreational vessels and ecotourism vessels. It's also military sonar. It's seismic air guns for offshore oil and gas exploration. It's you know, it's all of that.

AMY: Here’s what it sounds like in Glacier Bay, Alaska, with no engines running or other human-made noise closeby. Just a humpback whale making a call known as a “whup.”

HUMPBACK WHUP

AMY: And here's that same bay, with just one outboard motorboat in the water, and a humpback trying to sing.

HUMPBACK SINGING WITH BOAT

MUSIC

AMY: Our noise can be devastating for marine mammals. It can drive them away from their feeding areas, disrupt their migration routes, cost them valuable energy as they try to swim away from our din. Noise can be a factor in mass strandings, although the causes of those are notoriously difficult to pin down. But in addition to sudden, loud, explosive noises, our noise is a chronic problem for marine animals. All day and all night, all over the world, we are forcing ocean animals to shout to be heard—exhausting their resources, intruding on their mating rituals, and making it harder for families and friends to stay together. Sometimes they just give up, and fall silent when loud ships are around.

ICEBREAKER

AMY: This is what an icebreaking ship sounds like underwater as it moves through the Canadian Arctic.

Was it hard to hear me there? Exactly. That's the problem.

ICEBREAKER

AMY: I said, this is what an icebreaker sounds like underwater as it moves through the Canadian Arctic. Belugas have been documented scattering and making erratic dives in response to these kinds of noises. It looks a lot like a stress reaction, which makes sense when sound is the main way that these animals stay connected. Valeria has spent years quantifying the impact of anthropogenic noise on one population of highly endangered belugas in the St. Lawrence Estuary.

VALERIA: What noise does is it masks the sounds that little calves produce, and it prevents mothers from hearing their calves past a certain distance. So basically, noise can reduce the distance that a newborn calf could be heard by the adults in the group.

AMY: Imagine that you're walking through a city with a young child, and someone suddenly puts blindfolds on both of you. Blindfolds that you can't take them off—you just have to try to adapt. That might be how it feels for belugas and other marine mammals when we invade their territory with noise. It's not just an annoyance. It's a life threat.

VALERIA: Bioacousticians have the term acoustic fog, because for whales to exist, and to communicate, and to hunt, and to navigate immersed in underwater noise would be like for humans to try and conduct their lives in a thick layer of fog, because we are as visual as they are acoustic.

AMY:  In addition to their social communication, belugas use echolocation, or sonar, like dolphins do.

VALERIA: They use sonar to eat. They use sonar to navigate. So noise really compromises the ability of these animals to to conduct all of these very essential life functions.

AMY: Sound is important to other marine mammals too, like seals, sea lions, walruses, and manatees. And as we learned earlier this season, many kinds of fish communicate with calls and choruses.

REEF SOUNDS + FISH CALLS

AMY: Even creatures that don't produce sound, like octopuses, are often able to perceive it. We don't actually know how our noise is impacting most marine animals though, because we haven't studied them to find out. But given the power of sound in water, it's probably safe to assume that we are affecting things much more than we realize.

CHRISTINE: Underwater, you can hear things over very, very long ranges. So, for example, ships underwater, you might hear those for tens or hundreds of kilometers.

AMY: Christine Erbe is an expert in underwater sound.

CHRISTINE: So I'm Christine Erbe, I'm the director of the Center for Marine Science and Technology at Curtin University here in Perth, Western Australia.

AMY: I asked Christine which source of noise pollution was causing the most problems—shipping, fishing, tourism, seismic exploration. And she said: all of the above.

CHRISTINE: The big problem is the cumulative noise. If you're doing something on the eastern coast of South America, you might be able to actually even hear it on the western coast of Africa. So the sound might cross the Atlantic Ocean.

AMY: Yes, you heard her right – some sounds can cross oceans.

CHRISTINE: So the ocean is is layered. What that means is that sound propagates at different speeds, at different depths in the ocean.

AMY: These layers are a function of temperature, pressure, salinity and other variables. I'll spare you the physics and cut to the punchline: one of those ocean layers is like a secret passageway for sound—almost like a tunnel that prevents sound waves from escaping up toward the surface or down into the depths. Instead, acoustic vibrations bounce between the ceiling and the floor of this ocean layer, sending the sound waves flying forward over vast distances.

CHRISTINE: So there's a deep sound channel. So it's a channel in the ocean and if you can get sound into that channel, then it propagates over very, very far ranges. It basically crosses entire oceans.

AMY: The deep sound channel flows like an undulating ribbon through the oceans. In warm, mid-latitude waters it's about one kilometer below the surface. In polar regions it rises up to a much shallower level.

CHRISTINE: So that means if you have whales now in the polar regions—let's say you've got some fin whales calling in Antarctica— their sounds will couple right into the deep sound channel because that channel comes up to the surface in Antarctica. So that means if you're now six thousand kilometers away, if you can get your hydrophone now at one kilometer depth, which is where that channel is, you will hear these whales from Antarctica.

WHALE  SOUNDS

AMY: So if we can tap into the deep sound channel, what about the whales themselves? Do they use it to pass messages across the oceans? We don't know many details yet about how far different species of whales can hear, or in what ranges of pitches. The first direct test of baleen whale hearing happened just in 2024. But we do know that humpbacks, bowheads, and many other whales are very vocal, and that do sometimes coordinate their behavior even when they're far away from each other. So it's possible they're using the deep sound channel to stay in touch from hundreds or even thousands of miles away.

HUMPBACK

AMY: The deep sound channel is the original global communications network. All kinds of important sounds are moving through it every day. For example, Christine says there are underwater microphones permanently installed in the warm Indian Ocean…

CHRISTINE: ...and you can monitor individual icebergs calving in Antarctica with those recorders.

GLACIERS CALVING

AMY: So it's possible to monitor climate change at the poles from near the equator, just by listening. And Valeria Vergara says we need to integrate all of these different sounds—animal communication, our noise, and the sounds of a quickly-heating world—in order to really understand where we're at, and what needs to be done.

VALERIA: I cannot possibly be having a talk about belugas and not talk about climate change and about the fact that these are ice dependent species, and we're losing ice at an incredibly fast rate. We're losing key habitat for belugas and other ice-dependent species. And this is dire, and it's happening as we speak. So we stand to lose these animals. We need to, we need to act quickly.

AMY: We're making our oceans hotter and louder simultaneously. And then there's the plastic and chemical pollution we're adding to the waters. Solving any one of these problems won't fix the others, but whatever we can do to reduce stress on the animals that live in the ocean gives them a better chance at survival. And both Valeria and Christine say solutions do exist.

CHRISTINE: I think in general, the key is to make things quieter. Everyone who goes into the ocean produces sound. You just can't avoid it. So I think all of the stakeholders have to do their bit to try and make it quieter.

VALERIA: We can have acoustic sanctuaries, you know, that are off limits to boats and are quiet havens for whales essentially. And there are speed limits. So if you reduce the speed of a boat, it tremendously reduces its noise signature.

CHRISTINE: So the nice thing about sound in comparison to chemical pollution is the moment you switch it off, it's gone. So you don't need to now spend 30 years cleaning it up and, and you know, looking for your microplastics and so totally different problem so sound I always think it actually should be. Comparatively simple to to manage, because if you switch it off, it's gone, right? There and then.

MUSIC

VALERIA: There's all sorts of ship quieting technologies that are becoming better and better. Incentive programs from ports for big ships to be quieter. There's so many things that we can do.

CHRISTINE: Maybe you can move some shipping routes around. If you have critical habitat between islands and the mainland, maybe you need to move the shipping lane to the outside it. There isn't a general solution that applies to all problems. So you have to really look at different environments. What are the issues? What are those sensitive receptors, and what can we do about it? But I totally believe that this can be managed in a sustainable way.

VALERIA: There are so very few things in ecology and conservation that we can do something about very effectively, and with noise and sound we can.

AMY: We have a lot more to learn about how our noise is impacting other beings, in the air, on the ground, and in the water. But we do know two very important things now: noise pollution is serious and it’s solvable. And the research is clear that we need to solve it, not just for the health of other animals, but for our own.

We'll have more after this short break.

Break

[23:26] B SEGMENT

AMY: Welcome back to Threshold, I'm Amy Martin, and I'm standing next to the Arc de Triomphe in Paris, France. Multiple lanes of fast-moving traffic are circling around the huge monument—cars, buses, motorcycles, and occasionally bicyclists, who are giving me minor panic attacks as they navigate through the swirl. Paris is very beautiful. And this spot is very loud.

ANTOINE: In many, many cities around the world, it's the, it's the, what can I say? The legacy of the past. The 20th century was really the one where, urban planning was making more place for the cars.

AMY: Antoine Perez Muñoz is an expert in public and environmental health in Paris.

ANTOINE: Cars was the other word for progress, growth and so on. Now we pay the price.

AMY: When we met, Antoine was with Bruitparif, an agency focused on noise in the Paris region. Twelve million people live in this region, known as the Île-de-France, which includes the city itself, and the surrounding suburbs and countryside.

ANTOINE: Our main role is to document noise in order to tackle noise issues all around the region.

AMY: Paris is an interesting place to think about noise both because it's a real issue here, and also because people are doing things about it. Antoine has agreed to spend some time walking around the city with me, identifying noise problems and showing me some of the ways his group is helping to solve them.

ANTOINE: OK first I apologize, I speak English, maybe twice a year. So I do my best.

AMY: You sound great.

ANTOINE: OK, thank you.

AMY: We met in a neighborhood called Les Halles [lay-AHL], The Halls.

ANTOINE: So here we are in a very, specific area, which is the center of Paris. There was a book of French author Émile Zola, The Ventre de Paris, called The Belly of Paris. So this is the place where, many, major roads, many bus lines, many metro lines are all connected together.

AMY: In previous centuries there was a huge food market here, and a slaughterhouse. Today those things have been replaced by a shopping mall, a Metro station, and a large green space, with benches and wide walkways. Antoinne says a lot of space in this neighborhood that had been ceded to cars has been returned to bikers and walkers over the last several decades, and, unsurprisingly, road noise has gone down.

ANTOINE: Let's say 50 years ago, this was not a pedestrian area.

AMY: But….

ANTOINE: You just have to walk a hundred meters and then you find the cars.

ROAD NOISE

ANTOINE: Here you have the Boulevard de Sebastopol. It's a north-south important road, main road in Paris. And you find here that, noise, road noise is not completely pushed aside.

AMY: It's true, there is road noise here. But there are also frequent crosswalks, a lane dedicated to buses, and a wide two-way bike lane. For a main road in a big city, it doesn't seem all that loud to me.

AMY: There's a nice kind of steady flow of bikes over here and, and people on little electric scooters and things.

ANTOINE: 20 or 30 years ago. Very few people were, brave enough to ride bikes inside Paris.

AMY: But as we walk on through the city, I see a lot of bikers now. Antoine says car-reduction policies have been underway in Paris for a while, but the covid pandemic accelerated the process. As a temporary measure to reduce congestion on the Metro, additional bike lines were created on some major roads, and they proved so popular that they were made permanent.

MUSIC

AMY: People all over the world are trying to make their cities and towns quieter. It's a long term process that requires ordinary citizens pushing  for change, and political leaders willing to take risks. It’s about a lot more than trading out cars for bikes, Antoine says. Cities need to provide a high-quality menu of transport options to meet the needs of a diverse society—trains, buses, car share programs. And, he says, they need data.

ANTOINE: Here you find common sensors just dedicated to measure road noise.

AMY: He's pointing up at a device installed on the side of a building by his organization. It's not that big, and I probably wouldn't have noticed it on my own.

ANTOINE: So it's just one microphone. And this has been implemented maybe ten years ago. So we have a long view of the evolution of the roads and we see it's quieter than it was. We have the data.

AMY: Just like with air pollution or any other environmental problem, there's no way to make progress on noise if we don't measure it. This is one of the ways that Paris is emerging a global leader on noise pollution. The region has installed over 150 noise sensors, allowing them to get detailed information about where and when noise is spiking, and what's causing it. Some of these devices have multiple microphones and a camera, which makes it possible to identify chronic noise offenders, like bars that violate quiet hours, or motorcyclists who jerry rig their bikes to make them extra loud.

ANTOINE: This type of device allows us to locate. And the next step, of course, is to act.

AMY: So making our cities more peaceful requires a combination of all of these different elements, Antoine says: transportation options, data collection, and a lot of green spaces available to anyone looking for respite from noise.

ANTOINE: It's important that next to these commercial areas city planners have not forgotten to add quiet areas, peaceful areas, natural areas where people could just sit, talk, rest.

AMY: Sometimes in the U.S. I've heard the complaint that noise pollution is just a rich person's problem. It's just rich people trying to control everyone, they want to have a perfect little quiet paradise just for themselves. Do you hear that here, and what's your response to that?

ANTOINE: It's partially true. Yes. But, there's no...you can't have a straight opinion about that.

AMY: Antoine says that wealthier people may raise noise issues more often in part because they feel like they have more power to change the situation, where people in poorer neighborhoods might be more likely to feel like they simply have to adapt to noise. But that doesn't mean they're not experiencing the impacts.

ANTOINE: There's a ring road around Paris, which is a highway, and, most people who live around along the Paris ring road are the poorest of the area. You can say the same about the cities, that are close to the airports. Of course they are mainly poor cities, and…

AMY: And they're getting a lot of noise.

ANTOINE: Yes.

AMY: Exposure to noise pollution doesn't track perfectly with socio-economic status, Antoine says. For example, some of the most expensive housing in the city is close to the Champs-Élysées, where road noise is also high. But in general, lower income people are exposed to more noise. Antoine says there are multiple factors behind this. In addition to often being located next to highways and airports, cheaper housing is frequently less well-insulated, which makes a huge difference in terms of how much sound enters peoples' homes, disrupting their sleep and generally raising stress levels. But again, these are solvable problems, he says.

ANTOINE: The municipality of Paris has, decreased the speed limit on the ring road. They have also, they use now, silent coatings for the the asphalt of the, of the road that, can, decrease, the noises of the of the, of the roads and they have the, the plan to turn it from, from a highway to urban boulevard.

AMY: There are solutions for airport noise as well. Airplanes can be built with much quieter and more efficient engines, and landing routes can and are being designed so planes spend less time circling in the air, burning up fuel and spraying noise over a neighborhood. Making these sorts of changes—or failing to make them—has real consequences.

ANTOINE: It has an impact on people's health. It's now well documented, the connection between the exposure to noise and sleep disturbance, diabetes, cardiac diseases, hypertension. There are many studies now that, make the connection between the two. So it has an impact in terms of public health.

AMY: And those impacts are felt by people–especially lower income people—around the world.

METTE: If we look at the data we have, my evaluation is that we can say that road traffic noise increases risk of ischemic heart disease. It increases the risk of stroke. There are also a lot of studies showing it increases the risk for heart failure.

AMY: Mette Sørensen is a senior scientist at the Danish Cancer Society, and one of the world's leading researchers on noise and human health.

METTE: There are also many studies pointing in their exactly same direction with regard to type two diabetes. So I think, we can also say now that road traffic noise is associated with a higher risk of type two diabetes. So you can say this is what we know because you we have a large amount of data already. Then there are this where we need more data.

AMY: Mette says noise pollution has not been studied for nearly as long as other environmental hazards, like air and water pollution. But as awareness grows about the impacts of noise, more research is being done, especially in countries like Denmark with a wealth of robust data on where people live and what their health outcomes are. She's cautious about making any sweeping claims, but she says noise does appear to be an overlooked risk factor in a variety of health issues. She and her colleagues are studying connections between noise and dementia, some types of cancer, and even infertility.

METTE: So there are some there are a number of diseases where we still need more information. Whereas for the cardiovascular disease and type two diabetes, we know now that road traffic noise is a risk factor for these diseases.

MUSIC

AMY: So how much of an impact does noise really have? Like other environmental hazards, it's all about increased risk—we can't say for example “noise causes stroke,” but rather, “noise can increase your risk of stroke.” Mette says in one study of the entire Danish population, she found that a ten decibel increase in road traffic noise increased the risk for having a stroke by around four percent.

And just like with whales and other non-human animals, the link is stress. Noise can trigger flight or fight responses, causing our bodies to release adrenaline and cortisol, hormones that put us into an alarm state. And this makes sense. We evolved in a much quieter world, and we survived by being highly sensitive to the sounds around us. It's very useful to get woken up by noise if it's caused by a hungry bear trampling around outside your cave—less so when it's a highway or an airport that you can't get away from, or do anything about. Even when we're not aware of being bothered by noise, it may pull us out of deep sleep again and again throughout the night.

METTE: We know that disturbance of sleep is really a huge risk factor for diabetes. So we did I think three or four studies. And they really consistently show that road traffic noise is a risk factor for developing type two diabetes.

AMY: And it's not just about sleep. Many of us are exposed to loud sounds throughout the day, and throughout our lifetimes. 

METTE: There are some studies on aircraft noise from the UK where they looked actually in children around the Heathrow airport, and found that aircraft noise at schools were associated with lower reading comprehension, for example.

AMY: We also don't know much yet about what happens when exposure to noise is combined with other environmental risk factors, like air pollution, or heat exposure. And we need to do a lot more research on how much noise in the workplace impacts our health.

METTE: If we work noisy, we sleep noisy, it's noisy all the time. So is it kind of that your body cannot restore at any time during daytime or nighttime because there's always some sort of noise around you.

AMY: Mette and other scientists are doing the crucial work of putting hard numbers on how noise hurts our health. But I think  there’s a whole sphere of damage here that’s much harder to quantify, but no less important. It’s psychological. Spending our lives trapped inside our own noise feels almost like mass psychosis to me, or some gargantuan, collective narcissism. And it’s lonely inside all this noise. We used to move through the world knowing ourselves to be players in a big complex orchestra, members in a choir of life. Now, for the first time in our long evolutionary history, we wander alone, talking and listening only to ourselves.

AMY: I know that depression, anxiety, and other mental health issues are complex, and can never be attributed to just one thing. But I have to wonder if this sonic solitary confinement we’ve condemned ourselves to is part of the reason so many of us feel hopeless and overwhelmed. I think we really need to hear the rest of life to be healthy. I know I do.

FROGS

AMY: And I know I’m not alone. I have hard evidence of that, actually. A few months ago we asked you to send us recordings of frogs and toads, and you delivered. We received around 50 submissions, and we hit our goal of hearing from frog-listeners from every continent but Antarctica. We're going to end this episode marinating in the beauty of these frog songs, with you, our listeners and producer Sam Moore, serving as our guides.

PULCHANA GLANDULOSA

SAM: Amphibians emerged over 300 million years ago, and for a long time they were the top predators on land. Some ancient amphibians grew to be more than three meters—ten feet long.

SAM: Some amphibians, like salamanders, have tails. Others don't. Frogs are anurans, which is Greek for "without a tail."

SAM: The ancient Egyptians associated frogs with fertility because when the Nile flooded, water returned to the land and with it came millions of frogs.

NIGHT CHORUS FROM BORNEO

VINCENT CHANTER: Hi, name is Vincent Chanter. These recordings were recorded in the country of Sarawak on the island of Borneo. At the time I visually identified the Harlequin tree frog, Dark-eared tree frog, File-eared tree frog, Wallace's flying frog, Green paddy frog, and Collette's tree frog.

SAM: There are more than 7,000 species of frogs on Earth, and we're still catching up with the total. The International Union for Conservation of Nature, or IUCN, estimates that about three new species are identified every week, or about 150 every year.

SAM: Amphibians are more threatened than any other vertebrate, and a higher percentage of amphibian species are threatened than even corals. More than 200 species have probably gone extinct in the past 40 years that we know about.

ANTILEAN WHISTLING FROG

AMERICAN TOAD CHORUS

SAM: The thing that makes frogs so vulnerable is exactly what makes them so special. They fully absorb the world around them through their permeable skin. They breathe and drink the world in with their whole bodies. So even though frogs get air mostly through their skin, they still have lungs. Why do they still lungs? Well, a big part of it is so they can make noise and hear their fellow frogs. Frogs' lungs are coupled directly with their ear drums and their mouths, forming one huge resonator.

SAM: Tadpoles have lungs too, a lot of them do, and can make sounds, but we just don't really know what they're saying or what those sounds mean.

IOWA FROG CHORUS

CRAIG: My name is Craig Hemsath, and this is a chorus of frogs, including the Northern chorus frog, American toad, and Cricket frog. It was recorded on a warm April evening in Iowa in the United States.

JENNY: Hi, I’m Jenny Skopliak from BC Canada, and this is my audio of the Pacific chorus frog.

PACIFIC CHORUS FROG

KLAARTJE: Ghent, Belgium. 

MYSTERY BELGIAN FROG

ADRIENNE: Adrienne Van Eeden-Wharton, Clicking Stream Frogs 

CLICKING STREAM FROGS

FIRE-BELLIED TOAD

PABLO: My name is Pablo Disarens. The frogs I have shared with you are the Common midwife toad and the Fire-bellied toad. I have recorded the call of the Common midwife toads in Spain, and I’ve recorded the calls of the Fire-bellied toads in Germany, in the countryside near the city of Karpus (sp?)

SAM: In midwife toads the midwife is actually the male toad. He's the one carrying the fertilized eggs around, and he keeps them safe on his back until they hatch.

GLADIATOR FROG

SMALL-HEADED DWARF TREE FROG

RED-EYED TREE FROG

SAM: Almost half of all amphibians are in Latin America and the Caribbean.

TÚNGARAS

SAM: Túngaras are small frogs that live in Latin America. Female túngaras are attracted to the males with the deepest voices. A deep voice means a large resonating chamber and a large frog. But unfortunately for male tungura frogs, there are other creatures listening to their deep voices too, which include blood-sucking flies and frog-eating bats. Which means that if you're a Tungara frog dude winning the singing contest might mean you get eaten by a bat.

MYSTERY FROG CHORUS FROM MASSACHUSETTS

CURT: My name is Curt Newton. There’s a glorious chorus of frogs in a pond in the Blue Hills Reservation, Milton, Massachusetts.

DIOGO: Hi, my name is Dogo Ferreira Machado Matias. I heard this frog in Italy. And the frog’s common name is the Pool frog. And the Latin name is Pelophylax lessonae.

POOL FROG

BESS: My name is Bess and this is a recording I made of the frogs in my backyard in Huntsville, Alabama in the United States. We believe them to be Cope's gray tree frogs.

COPE'S GRAY TREE FROGS

ECUADORIAN AMAZON FROG CHORUS

MYSTERY FROGS FROM KENYA

SAM: Frogs do hop, but they also swim, they dig, and they climb. And a few of them even glide through the air because they have huge webbed feet that they can use as parachutes.

PINE TOAD

SAM: Making all these sounds costs frogs a lot of energy. Many of them get skinnier and skinnier the longer and louder they call. And they're also devoting a lot of energy to listening. You can see how important hearing is to frogs just by looking at them—some of them have a conspicuous eardrum right behind their eye on the outside of their head.

PULCHRANA BARAMICA

SPRING PEEPERS

AARON: My name is Aaron Jonah Lewis, and I recorded these Spring peepers in Maine, USA.

MYSTERY FROGS FROM WASHINGTON

KIDDO: How’s it in there, in that water?

JOEL: This is Joel Waters recording in Anacortes, Washington.

GREEN FROGS

EDWARD: This is Edward Ruchalski. I recorded at Wave Farm in Accra, New York.

SAM: Human noise can stress frogs out. Traffic noise can trigger stress hormones in some species, just like it does for us. Noise pollution adds one more layer to the threats amphibians face.

SPADEFOOT

SAM: The first global meeting of frog scientists didn't happen until 1989. And when they met, almost every scientist had a story about a common frog that they had studied that was now rare, or a story of a once common frog that had become rare as they were studying it. Today, the IUCN says 41% of all amphibians are threatened with extinction.

MYSTERY FROGS FROM MUNAY SUYU, ECUADOR

MUSIC

AMY: Imagine a world without any of these sounds. Without birdsong. Without whale music. Without any other voices but our own. That’s the world more and more of us are living in. And the more noise we make, the more voices we fail to hear, and the easier it becomes to forget that those voices are even out there—to notice what we’re losing. It's a cascade of increasing disconnection, and it’s threatening to send us over a really scary cliff of mass extinction. 

AMY: But it can work the other way too. The more we listen to our planet-mates, and take in the wonder and mystery of their voices, the more we can feel our connection to them, and—hopefully—get inspired to act.

AMY: What if we insisted on healthy sonic spaces just like we insist on healthy water and air? What if we designed our cities and towns around the idea that all kids need and deserve to have easy access to places where they can hear birds and bugs and the whole mixture of sounds of a place; where our noise doesn't dominate everything? How would they be changed—how would we all be changed—if we lived inside soundscapes that constantly reminded us that we're not the only species in the room? Not the only voices that matter. That we're not alone.

Credits

AMY: This episode of Threshold was written, reported, and produced by me, Amy Martin, with help from Erika Janik and Sam Moore. Sam led Operation Frog Sound as we’ve been calling it here, and wrote all of the frog facts, as well as doing the fact-checking for the whole episode. Music by Todd Sickafoose. Post-production by Alan Douches. 

A lot of people deserve special thanks in this episode. Usually I use only sounds I’ve recorded to create the soundscapes you hear on our show, but in this episode, I drew on libraries of sounds recorded by dedicated marine biologists and other underwater sound lovers who’ve generously made some of their work available online. They include Richard Nelson and Hank Lentfer at the Glacier Bay National Park & Preserve, Thomas Kieckhefer, Denise Risch, Jennifer Miksis-Olds, Peter Scheifele and Sonatech, Inc., at Discovery of Sound in the Sea, the Ships, Whales & Acoustics in Gitga’at Territory Project, the National Oceanic and Atmospheric Administration, the Scripps Whale Acoustics Lab, Aarhus University, the Lofoten-Vesterålen Ocean Observatory, and Brian Miller at the Australian Antarctic Division. Additional thanks to Tim Lamont, Miles Parsons, and Valeria Vergara.

And then, there are all of you who submitted the sounds of frogs and toads. Thank you so much for sharing your amphibian calls with us—there are actually too many of you to name here, but we’re going to list all of you in the show notes. As you can hear, you made this episode so special. And speaking for myself, you also reaffirmed how many people all over the world are hungry to keep the connections with our planet-mates alive. Destruction is not humanity’s destiny, or our only story. We’re capable of profound appreciation for all the life around us. Thank you to everyone who sent in these beautiful sounds for reminding me of that.

Threshold is made by Auricle Productions, a non-profit organization powered by listener donations. You can find out more about our show and support our work at thresholdpodcast.org.

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