Transcripts
If you stand in front of a classroom full of
Amy Martin:kindergarteners and ask them what an ear is, chances are good
Amy Martin:that they'll think you're kind of silly. Everybody knows what
Amy Martin:ears are, those floppy things on the sides of our heads, the
Amy Martin:things we hear with but what if you were to pose that same
Amy Martin:question to a classroom full of spiders?
Amy Martin:Dr. Natasha Mhatre: So this is going into the fun part of my
Amy Martin:Dr Natasha Mhatre researches how insects and
Amy Martin:research.
Amy Martin:spiders process sound at the University of Western Ontario,
Amy Martin:and she says that scientists used to think that spiders
Amy Martin:couldn't hear airborne sound because they didn't seem to have
Amy Martin:any obvious ear like structures.
Amy Martin:Dr. Natasha Mhatre: That used to be the received wisdom. There's
Amy Martin:now different pieces of evidence from other labs, including some
Amy Martin:evidence we've just collected that suggest that they can hear
Amy Martin:airborne sound.
Amy Martin:Where would their ears be?
Amy Martin:Dr. Natasha Mhatre: So that's the big question.
Amy Martin:Natasha says she and other researchers are now coming
Amy Martin:to understand that it's not necessarily that spiders don't
Amy Martin:have ears. They might just look really different than ours.
Amy Martin:Dr. Natasha Mhatre: Okay, so there's some evidence that one
Amy Martin:of the ways that they hear is when air hits the web of some
Amy Martin:spiders, it makes the web move, and they can sense the vibration
Amy Martin:of the web, so they're kind of making their own ear drum.
Amy Martin:The web is the ear.
Amy Martin:Dr. Natasha Mhatre: The web is the ear.
Amy Martin:How cool is that?
Amy Martin:Dr. Natasha Mhatre: That is pretty neat, because you can
Amy Martin:make whatever ear you want, right? If it gets damaged, you
Amy Martin:can just make yourself a new ear. Really cool.
Amy Martin:Welcome to Threshold, I'm Amy Martin, and
Amy Martin:we're going to hear a lot more from Natasha in our next
Amy Martin:episode. But I wanted to start out with this fun little factoid
Amy Martin:about spiders just to shake up our perceptual framework. We
Amy Martin:think we know what ears are. We think we know what it means to
Amy Martin:listen, but those ideas are usually just drawn out of our
Amy Martin:own very limited experience. And speaking of things we think we
Amy Martin:know but maybe don't, what is sound? Like, if you had to
Amy Martin:define it right now without looking anything up, what would
Amy Martin:you say? Even though I work in audio, I didn't really have a
Amy Martin:clear answer to that question before making this season of our
Amy Martin:show. Sound is one of those things that's so much a part of
Amy Martin:my everyday life that it's easy to forget how mysterious it
Amy Martin:really is. It's everywhere, but it's invisible. It's flowing
Amy Martin:into my brain every waking moment and when I'm asleep it
Amy Martin:turns out, affecting my mood, my energy level, my sense of
Amy Martin:connection to wherever I am and whoever I'm with. But what is it
Amy Martin:actually? The answer to that question is not as
Amy Martin:straightforward as you might expect, so in this episode,
Amy Martin:we're going to press pause on our timeline of listening to
Amy Martin:examine the nature of sound itself, what it is, how it
Amy Martin:moves, and how wildly different our experiences of it can be.
Amy Martin:We're going to tap into a secret communication network happening
Amy Martin:all around us, pay another visit to the dolphins of Shark Bay and
Amy Martin:talk to a world famous composer about how much more there is to
Amy Martin:listening than what meets the ear.
Amy Martin:I'm walking through a Montana forest. The breeze is rustling
Amy Martin:through the trees. There's a creek flowing nearby, and one of
Amy Martin:my favorite birds is unleashing its song again and again. It's a
Amy Martin:Swainson's thrush, and I love its song. I think it sounds like
Amy Martin:a waterfall flowing up. Chances are good that you have a bird
Amy Martin:song you love too, and even if you don't, almost all of us hear
Amy Martin:birds singing every day. So in a way, this experience I'm having
Amy Martin:is completely ordinary. But if I zoom out a bit and think about
Amy Martin:what's actually happening here, it's kind of marvelous.
Amy Martin:Something that originates inside the body of a small bird hidden
Amy Martin:in the branches above me is traveling across the forest and
Amy Martin:landing inside my ears and ultimately in my mind, where it
Amy Martin:becomes this beautiful, melodic thing with the power to change
Amy Martin:my mood and lift my spirits. I'm receiving something from this
Amy Martin:thrush, something is being transferred between us, and it's
Amy Martin:affecting me. But what is that something exactly? What is
Amy Martin:sound?
Amy Martin:Dr. Lily Wang: So at its heart it is an energy in the form of
Amy Martin:vibrational waves in matter.
Amy Martin:Dr Lily Wang is an engineer who teaches and studies
Amy Martin:acoustics at the University of Nebraska in Lincoln. She fell in
Amy Martin:love with sound as a child the way many people do: through
Amy Martin:music.
Amy Martin:Dr. Lily Wang: I love singing. I have loved singing since I was a
Amy Martin:little girl, and I've always been in choirs, and then I did
Amy Martin:also play piano.
Amy Martin:I asked Lily to give me a crash course in the
Amy Martin:fundamentals of sound, and she started with the fact that
Amy Martin:there's a wide range of sound waves, and we can only hear a
Amy Martin:portion of them.
Amy Martin:Dr. Lily Wang: We call it the audible range. The most common
Amy Martin:definition of the audible range is 20 hertz to 20,000 hertz.
Amy Martin:To help make those numbers mean something, here's a
Amy Martin:tone moving across that whole range. It takes about 30
Amy Martin:seconds.
Amy Martin:But this so called audible range should really be called the
Amy Martin:human audible range. Elephants, pigeons and many other animals
Amy Martin:can hear well below what we can detect, that's called infrasound
Amy Martin:and all sorts of other creatures can hear way higher than we can
Amy Martin:in the ultrasound range. Dogs can pick up frequencies twice as
Amy Martin:high as our upper limit. Cats can hear four times higher. And
Amy Martin:many dolphins can hear seven or eight times higher than us, up
Amy Martin:to 150,000 hertz. That's higher than almost all other
Amy Martin:vertebrates on the planet, except bats. Again, humans top
Amy Martin:out at around 20,000 hertz, or for many of us, significantly
Amy Martin:lower.
Amy Martin:Dr. Lily Wang: I really can't hear above 8,000 hertz anymore.
Amy Martin:You know, there are bats in my house at certain times of the
Amy Martin:year, and I cannot hear them. Like I can see my children go...
Amy Martin:woo!..they twist their heads like they can hear that the bats
Amy Martin:are back and they're nesting, sadly, in our house, and they're
Amy Martin:like, squeaking, but it's at like, it's probably at like, 10,
Amy Martin:12,000, hertz. I do not hear it at all.
Amy Martin:Here's what 10,000 hertz sounds like. If you're not
Amy Martin:hearing anything, don't worry. You are definitely not alone.
Amy Martin:Dr. Lily Wang: It's the most common disability among humans
Amy Martin:is that we lose hearing and most often at that higher frequency.
Amy Martin:In fact, some amount of hearing loss is almost
Amy Martin:inevitable as we age and of course, some people don't hear
Amy Martin:any airborne sound at all. We're going to talk to one of those
Amy Martin:people later in this episode, but Lily says this measurement
Amy Martin:of how we hear sound waves moving through the air is really
Amy Martin:just one relatively narrow dimension of our lived
Amy Martin:experience of sound. All kinds of other factors affect our
Amy Martin:listening experience, the temperature and humidity of the
Amy Martin:air, what other sounds are happening at the same time, the
Amy Martin:shape and texture of the space we're in, and that includes the
Amy Martin:most intimate space of all, our own individual bodies.
Amy Martin:Dr. Lily Wang: The shape of your ear, the shape of your head, the
Amy Martin:shape of your body, all these things are affecting how that
Amy Martin:sound wave approaches you.
Amy Martin:This is why our voices sound weird in our own
Amy Martin:ears. When we hear ourselves on recordings, we're actually
Amy Martin:experiencing the sound very differently when it's coming at
Amy Martin:us in the air through a speaker, versus hearing it from inside
Amy Martin:the place it's produced, the resonating chambers of our own
Amy Martin:bodies.
Amy Martin:Dr. Lily Wang: The fact that we are part of this experience does
Amy Martin:actually morph how that wave gets into our head.
Amy Martin:So you and I could be walking right next to each
Amy Martin:other listening to the same Swainson's thrush calling in the
Amy Martin:forest, and the differences in the shapes of our bodies means
Amy Martin:we'll be hearing slightly different things. But however
Amy Martin:the sound waves are ultimately received, they all start the
Amy Martin:same way, with a vibration.
Amy Martin:Dr. Lily Wang: Something that is moving, something back and
Amy Martin:forth.
Amy Martin:From there, a whole lot of things happen one after
Amy Martin:the other really, really quickly. So let's try to follow
Amy Martin:the journey of that Swainson's thrush song step by step, from
Amy Martin:creation to reception. In birds, as with humans, song begins with
Amy Martin:breath. This thrush pushes air out of its lungs and through a
Amy Martin:special organ called the syrinx. It's set up differently from the
Amy Martin:human larynx or voice box, but the basic concept is the same.
Amy Martin:The bird squeezes the muscles around the syrinx, setting air
Amy Martin:molecules into motion, and when it opens its mouth, that
Amy Martin:vibration is then passed through the air, molecule to molecule
Amy Martin:like a baton.
Amy Martin:Dr. Lily Wang: It's pushing these particles, which push the
Amy Martin:next particles, which push the next particles.
Amy Martin:It's an incredibly fast relay race, moving from the
Amy Martin:bird across the forest and into my ears.
Amy Martin:Dr. Lily Wang: But once it gets into the ear, it's traveling
Amy Martin:down and it eventually hits a membrane that is physically
Amy Martin:attached to three of the smallest bones in your body.
Amy Martin:That membrane is called the eardrum, and it is a
Amy Martin:lot like the tight, bouncy top of the drums we use to make
Amy Martin:music, except it's only about a centimeter wide. That's less
Amy Martin:than half an inch, the vibrating molecules of air hit that drum,
Amy Martin:making it shake, and that causes those teeny, tiny bones called
Amy Martin:the ossicles to move, one after the other, which shakes a second
Amy Martin:membrane...
Amy Martin:Dr. Lily Wang: ...that is then connected to fluid inside the
Amy Martin:cochlea.
Amy Martin:The cochlea is a fluid-filled tube coiled up like
Amy Martin:a snail shell or the world's tiniest cinnamon roll, and when
Amy Martin:the vibration that began with the breath of the bird is
Amy Martin:transferred into the cochlea, it sends ripples through the fluid
Amy Martin:inside, almost like waves rolling across a miniature
Amy Martin:ocean. And lining the inside of the cochlea, swaying in the
Amy Martin:fluid, guess what we find? Cilia. Tiny little hairs like
Amy Martin:the ones that grow on the bodies of baby corals. Under a
Amy Martin:microscope, they look like sea grasses, flexing and bending as
Amy Martin:the waves of sound roll over them.
Amy Martin:And as they move in response to the sound energy, the cilia
Amy Martin:perform one of the greatest magic tricks in the human body.
Amy Martin:They transform this physical vibration into a spark of
Amy Martin:electricity, which then shoots off to the brain through the
Amy Martin:auditory nerve, where we process it as a sound.
Amy Martin:Dr. Lily Wang: And all this happens so fast, like, so fast,
Amy Martin:like, in an instant!
Amy Martin:343 meters per second, give or take, that's
Amy Martin:more than three football fields in the snap of a finger.
Amy Martin:Dr. Lily Wang: So quickly. It's just miraculous.
Amy Martin:So to recap the process, the vibration starts in
Amy Martin:the body of the bird. That energy is passed across the
Amy Martin:forest into my ear canals, where it hits the drum that moves the
Amy Martin:bones that hit the other drum that shakes the fluid, which
Amy Martin:bends the cilia that turn the vibration into electricity that
Amy Martin:goes to my brain, in less than a second. And that's the
Amy Martin:simplified version, but as quickly as this vibration is
Amy Martin:transferred from the bird to me as I walk through the forest,
Amy Martin:the movement of sound and air is actually relatively slow. Sound
Amy Martin:moves more than four times faster in water compared to the
Amy Martin:air.
Amy Martin:Dr. Stephanie King: This, this.
Laura Palmer:This is what we do.
Laura Palmer:Dr. Stephanie King: This is it. This is paradise.
Amy Martin:We'll have more after this short break.
Amy Martin:Welcome back to Threshold, I'm Amy Martin, and I'm in Shark
Amy Martin:Bay, Western Australia, scanning the horizon for dolphins.
Amy Martin:I keep seeing something way out there.
Amy Martin:Dr. Stephanie King: Yeah, that was another dolphin. Yeah, yeah.
Amy Martin:That's Stephanie King, co-director of Shark Bay
Amy Martin:Dolphin Research.
Amy Martin:Dr. Stephanie King: So we're approaching what we call glass.
Amy Martin:There's hardly any wind, and then you really see how many
Amy Martin:dolphins there are in Shark Bay, because you just start to see
Amy Martin:them everywhere.
Amy Martin:So cool.
Amy Martin:In our first episode, we met Stephanie and her field team and
Amy Martin:a few of the two or 3000 dolphins that live in these
Amy Martin:waters. Now it's the afternoon of that same day. The heat is
Amy Martin:upon us, the wind has died down, and we're moving slowly across
Amy Martin:the water.
Amy Martin:It's the most beautiful, blue, green water, it's just perfect.
Amy Martin:Up ahead, a small group of dolphins is gathered at the
Amy Martin:surface. They're not swimming or jumping. They're just kind of
Amy Martin:hanging out there in the calm, quiet waters. Stephanie explains
Amy Martin:what's going on.
Amy Martin:Dr. Stephanie King: You'll sometimes see dolphins in Shark
Amy Martin:Bay, what we call snagging. This is when they're resting at the
Amy Martin:surface, so the whole body's just flat on the surface. And it
Amy Martin:was because in Australia, you snag sausages on the barbie,
Amy Martin:like snagging. They're called snaggers on the barbie, and it
Amy Martin:looks just like a sausage lying at the surface.
Amy Martin:But these floating sausages are actually much more
Amy Martin:active than they appear. A dolphin doesn't lose
Amy Martin:consciousness when it rests, or at least not all the way. Half
Amy Martin:of its brain remains engaged in the work of breathing, which it
Amy Martin:needs to come to the surface to do, and stays alert to what's
Amy Martin:happening around it, and that means listening.
Amy Martin:Researcher Laura Palmer flips on the speaker in the boat
Amy Martin:connected to the underwater microphones, and we're suddenly
Amy Martin:dropped into a conversation.
Amy Martin:These are echolocation buzzes, pulses of sound that the
Amy Martin:dolphins send out in order to gather information about their
Amy Martin:world.
Amy Martin:Dr. Stephanie King: They wait for the returning echo, and so
Amy Martin:the closer they get to a fish, the more they are echolocating
Amy Martin:so they can use their returning echo to work out distance and
Amy Martin:shape.
Amy Martin:It's remarkable to be able to listen in as the
Amy Martin:dolphins do this, but it would be even more mind blowing to
Amy Martin:experience these sounds the way they do. Dolphins aren't only
Amy Martin:detecting a much wider range of sounds than we do, the whole
Amy Martin:nature of their sonic experience is something we can only sort of
Amy Martin:guess at. These echolocation buzzes are beams of acoustic
Amy Martin:attention, and they come back to the dolphins packed full of
Amy Martin:information that their brains have evolved to process at
Amy Martin:lightning speed.
Amy Martin:So what sounds to us like a continuous buzz, to them, it's
Amy Martin:like really fast echo locating happening?
Amy Martin:Dr. Stephanie King: Exactly. Really, really fast clicks. So
Amy Martin:they're like pulsed vocalizations, and they produce
Amy Martin:them so rapidly, so sometimes it sounds like it's almost a
Amy Martin:continuous vocalization.
Amy Martin:Dolphins can actually use echolocation to
Amy Martin:perceive the insides of objects. If I jumped in the water with
Amy Martin:this group, they'd be able to sense not just my outer
Amy Martin:surfaces, but my bones and lungs. They would perceive me in
Amy Martin:a way I could never perceive myself, and they'd be doing it
Amy Martin:using sound.
Amy Martin:Dr. Stephanie King: Here we go, snaggers.
Amy Martin:We've come upon another group of resting
Amy Martin:dolphins.
Amy Martin:Dr. Stephanie King: Snagging, see. Just resting at that
Amy Martin:surface, like a...
Amy Martin:Sausage on the barbie.
Amy Martin:Dr. Stephanie King: Sausage on the barbecue. Exactly.
Amy Martin:Stephanie says dolphins use echolocation
Amy Martin:primarily to help them find food and for navigation. But even
Amy Martin:now, when they appear to be doing little to nothing, there
Amy Martin:is some echolocating going on. It's like they're casually
Amy Martin:scanning the environment, just keeping the ear out, except that
Amy Martin:ear isn't where we might expect it to be on their bodies.
Amy Martin:Dr. Stephanie King: They receive sound through the lower jaw, and
Amy Martin:that sound then goes up to the middle and in the ear. So when
Amy Martin:they're snagging like that and resting, you sometimes see them
Amy Martin:their lower jaw is still in the water, and they're kind of
Amy Martin:moving their head side to side, as if they're scanning, right?
Amy Martin:They're not vocalizing. They're actually listening for sounds of
Amy Martin:other dolphins, if you like. So we typically see that when maybe
Amy Martin:they're waiting for a dolphin to catch up, or there's about to be
Amy Martin:a join, and they'll turn around and they're scanning, and
Amy Martin:they've obviously detected something, and then they're
Amy Martin:having a good listen to see who might be close by.
Amy Martin:But with dolphins and other animals that live in
Amy Martin:the water, the whole idea of close by has to be redefined.
Amy Martin:Acoustic vibrations don't only happen faster underwater than in
Amy Martin:air, they also do a better job of holding on to their power as
Amy Martin:the vibration is transferred from molecule to molecule, it
Amy Martin:doesn't lose as much energy with each pass of the baton, and that
Amy Martin:means underwater sounds can stay loud for a much longer time. So
Amy Martin:what feels very far away in human terrestrial life might
Amy Martin:feel quite nearby to a fish or a seal or a dolphin.
Laura Palmer:And Rockette just surfaced 80 degrees.
Amy Martin:There's a little flurry of extra buzzing from the
Amy Martin:group as a dolphin named Rockette pops up and joins them,
Amy Martin:but there's no visible change in the dolphins' faces. It's not
Amy Martin:like they're opening their mouths to echolocate. I asked
Amy Martin:Stephanie how they are producing these sounds, and she says, as
Amy Martin:with our vocalizations, it begins with air pushing through
Amy Martin:tissues in the dolphins' bodies.
Amy Martin:Dr. Stephanie King: They basically have these phonic
Amy Martin:lips, these two lips they can push together and then force air
Amy Martin:through that then causes vibrations of different tissues
Amy Martin:within that chamber. And it's the tissue vibration which
Amy Martin:creates the sound, essentially.
Amy Martin:I love how they're performing, right on cue, as
Amy Martin:you're talking about it, they started doing it.
Amy Martin:Dr. Stephanie King: Yeah!
Amy Martin:That vibration then passes through a pillow of fatty
Amy Martin:tissue in their foreheads called the melon. It acts as a sort of
Amy Martin:acoustic lens, focusing and amplifying the sound, which is
Amy Martin:then project it out through their heads. We think of making
Amy Martin:sound as one thing and receiving it as another, but one of the
Amy Martin:things I find most intriguing about echolocation is that it's
Amy Martin:both at once. It's a way of making sound in order to listen.
Amy Martin:It takes the whole idea of active listening to a completely
Amy Martin:different level. Dolphins can decide to shoot a beam of
Amy Martin:listening toward another dolphin or an approaching fish, kind of
Amy Martin:like the way we might flip on a flashlight in order to see into
Amy Martin:a dark corner of a room. And they can manipulate that
Amy Martin:echolocation beam, they can make it stronger or weaker, wider or
Amy Martin:narrower, and if something attracts their attention, they
Amy Martin:can turn up the dial instantaneously and send out a
Amy Martin:bright, strong pulse of acoustic energy homing in on whatever it
Amy Martin:is they want to investigate. That's what seems to have
Amy Martin:happened with Rockette, because she suddenly left her group and
Amy Martin:zoomed right under our boat.
Amy Martin:Dr. Stephanie King: There we go, Rockette in the bow. Hi,
Amy Martin:Rockette!
Amy Martin:Oh, hi. Hey, beauty. Oh, right underneath us. Oh, my
Amy Martin:gosh. I mean I can reach out my hand and touch her. Wow.
Amy Martin:It's not us she's curious about it's a patch of sea grass below
Amy Martin:us in the crystal clear water, we can see her twisting and
Amy Martin:turning herself through it.
Amy Martin:Dr. Stephanie King: So we saw Rockette just come up and rub
Amy Martin:herself in a sea grass patch. And we see that a lot with the
Amy Martin:dolphins, and we'll call it seagrass play. Or they seem to
Amy Martin:come up and drape it over their body and even rub themselves
Amy Martin:against it, I think just because it feels nice. But you see that
Amy Martin:quite often. And she obviously peeled off from the group,
Amy Martin:spotted that seagrass patch and went over there and started
Amy Martin:rubbing herself underneath it before returning to the group.
Amy Martin:It looked a little bit like a dog growing on a mat.
Amy Martin:Dr. Stephanie King: Yeah, exactly, and you know, they do
Amy Martin:that. It's fun. They enjoy. It feels good. Same for the
Amy Martin:dolphins.
Amy Martin:Lots of animals use echolocation, orcas and sperm
Amy Martin:whales, some small burrowing land mammals, and, of course,
Amy Martin:the most famous echolocators of all, bats. The common
Amy Martin:denominator here is darkness, where vision is diminished, the
Amy Martin:clicks, chirps and buzzes of echolocation can help animals
Amy Martin:navigate their worlds, and humans can learn to echolocate
Amy Martin:too. Many people with visual disabilities become experts in
Amy Martin:it, but even the most highly skilled person can't come close
Amy Martin:to what dolphins can do.
Amy Martin:Echolocation is only one of the ways dolphins use sound in
Amy Martin:future episodes, we'll be coming back to Shark Bay to listen to
Amy Martin:their whistles and pops, sounds they use to communicate with
Amy Martin:each other and even to identify themselves. But now it's time
Amy Martin:for us to return to the terrestrial realm, to meet these
Amy Martin:mysterious creatures that are using sound in yet another
Amy Martin:fascinating way. We'll have more after this short break.
Matt Hurley:Hi, my name is Matt Hurley, and I've been a
Matt Hurley:Threshold listener and donor since season one came out in
Matt Hurley:2017. I was also one of the first volunteer board members of
Matt Hurley:the nonprofit organization that makes Threshold. Over the past
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Matt Hurley:the time, the dedication, the determination that's required to
Matt Hurley:tell these, in depth stories really make people think and
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Amy Martin:Hi Threshold listeners. Do you ever find
Amy Martin:yourself wondering what businesses are doing and what
Amy Martin:more they should do to confront climate change? Then you should
Amy Martin:check out Climate Rising, the award winning podcast from
Amy Martin:Harvard Business School. Climate Rising gives you a behind the
Amy Martin:scenes look at how top business leaders are taking on the
Amy Martin:challenge of climate change. The show covers cutting edge
Amy Martin:solutions, from leveraging AI and carbon markets to sharing
Amy Martin:stories that inspire climate action. Recent episodes feature
Amy Martin:insightful conversations with leaders like Netflix's first
Amy Martin:sustainability officer, Emma Stewart, who discusses how the
Amy Martin:global entertainment giant uses its platform to promote climate
Amy Martin:awareness. You'll also hear from CNN's chief climate
Amy Martin:correspondent, Bill Weir, about the importance of integrating
Amy Martin:climate change into news coverage. Each episode dives
Amy Martin:deep into the challenges and opportunities that climate
Amy Martin:change presents to entrepreneurs and innovators. Listen to
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Amy Martin:Spotify, or wherever you get your podcasts.
Dallas Taylor:I'm Dallas Taylor, host of 20,000 Hertz, a
Dallas Taylor:podcast that reveals the untold stories behind the sounds of our
Dallas Taylor:world. We've uncovered the incredible intelligence of
Dallas Taylor:talking parrots.
Unknown:Basically, bird brain was a pejorative term, and here
Unknown:I had this bird that was doing the same types of tasks the
Unknown:primates.
Dallas Taylor:We've investigated the bonding power
Dallas Taylor:of music.
Unknown:There's an intimacy there in communicating through
Unknown:the medium of music that can be really a powerful force for
Unknown:bringing people together.
Dallas Taylor:We've explored the subtle nuances of the human
Dallas Taylor:voice.
Unknown:We have to remember that humans, over many hundreds
Unknown:of thousands of years of evolution, have become extremely
Unknown:attuned to the sounds of each other's voices.
Dallas Taylor:And we've revealed why a famous composer
Dallas Taylor:wrote a piece made entirely of silence.
Unknown:I think that's a really potentially quite useful and
Unknown:quite profound experience to have.
Dallas Taylor:Subscribe to 20,000 Hertz right here in your
Dallas Taylor:podcast player. I'll meet you there.
Dallas Taylor:Dr. Rex Cocroft: So now we're hearing their mating signals.
Amy Martin:Welcome back to Threshold, I'm Amy Martin, and
Amy Martin:we're back in the United States now with Dr Rex Cocroft and a
Amy Martin:group of wild animals. I'm not going to tell you what they are
Amy Martin:right away, just listen and guess.
Amy Martin:Dr. Rex Cocroft: Two or three different males.
Amy Martin:So cool.
Amy Martin:Here's a hint. These animals are much, much, much smaller than
Amy Martin:dolphins. They live all over the world, and millions of people
Amy Martin:walk by them every day as they make these sounds. But we don't
Amy Martin:hear a thing. This sound is made by a treehopper, a teeny little
Amy Martin:insect about the size of a sunflower seed without the
Amy Martin:shell. It communicates by shaking its abdomen, which sends
Amy Martin:waves of vibrations through its legs and out into the stems and
Amy Martin:leaves of plants. Other tree hoppers can feel those
Amy Martin:vibrations with their legs, and they often respond with their
Amy Martin:own belly shakes.
Amy Martin:Dr. Rex Cocroft: And it doesn't look like they're doing anything
Amy Martin:at all. There's stationary. If you're really close, you can see
Amy Martin:their abdomen moving when they signal. But otherwise it just
Amy Martin:looks like like nothing is happening.
Amy Martin:And ordinarily it also doesn't sound like anything
Amy Martin:is happening. These treehopper calls don't get broadcast out
Amy Martin:into the open air. It's not just that these insects are small and
Amy Martin:their calls are quiet. The vibrations they make don't leave
Amy Martin:the body of the plant. We're only able to hear them now
Amy Martin:because Rex has hooked up a special microphone to the plants
Amy Martin:and connected it to some speakers.
Amy Martin:Dr. Rex Cocroft: If I turn the speaker down, you don't hear
Amy Martin:anything. And we're standing right next to this plant, and
Amy Martin:you could put your ears right next to me, you really don't
Amy Martin:hear anything.
Amy Martin:So these little insects are talking to each
Amy Martin:other through a secret world of sound called the vibroscape.
Amy Martin:Instead of air or water, these acoustic waves are moving
Amy Martin:through the bodies of living plants.
Amy Martin:Dr. Rex Cocroft: It's like they take a different train, sec
Amy Martin:through acoustic space and put together sound in ways that we
Amy Martin:never thought to do.
Amy Martin:So what is going on here? How is it possible that
Amy Martin:these sounds are happening all around us, but we can't hear
Amy Martin:them? and how did Rex break the code? Well, it helps that he had
Amy Martin:an early interest in music like Lily Wang, and later he combined
Amy Martin:that with a love of biology and animal communication. He studied
Amy Martin:frogs at first, but one day in the 1990s, Rex decided to find
Amy Martin:out if treehoppers had anything to say.
Amy Martin:Dr. Rex Cocroft: I just walked out onto a meadow near where I
Amy Martin:lived. I was at Cornell, so this was upstate New York, very
Amy Martin:beautiful place in the summer. I had a tape recorder. It was a
Amy Martin:cassette tape recorder and headphones.
Amy Martin:He found a goldenrod plant with some tree hoppers on
Amy Martin:it, and leaned a microphone right up against it.
Amy Martin:Dr. Rex Cocroft: And immediately I heard these wonderful sounds.
Amy Martin:I'd never heard it before, this tiny insect, this beautiful
Amy Martin:song. And then I was hooked. I never looked back. It was a
Amy Martin:sound that I was completely unfamiliar with, and I could be
Amy Martin:confident that no human had ever heard that sound before, and
Amy Martin:that's still true with most, most insects that communicate
Amy Martin:through plants. You listen to them, and probably nobody's ever
Amy Martin:heard that sound before.
Amy Martin:And that's basically just because we haven't been
Amy Martin:listening. We couldn't hear anything, so we thought there
Amy Martin:was nothing to hear.
Amy Martin:It's almost like the treehoppers turn the plants and their own
Amy Martin:bodies into musical instruments. That's partly what captivated
Amy Martin:Rex about these sounds the first time he heard them.
Amy Martin:Dr. Rex Cocroft: To me, it was totally different when I
Amy Martin:expected, because it had, it was like harmonically structured,
Amy Martin:and it was changing in pitch, and it was very exciting.
Amy Martin:Before we knew anything about their sonic
Amy Martin:lives, treehoppers had attracted attention because of their
Amy Martin:appearance.
Amy Martin:Dr. Rex Cocroft: They look like miniature cicadas, and they have
Amy Martin:a kind of roof over their back that in many cases, is very
Amy Martin:elaborate and whose function we still don't really know in many
Amy Martin:cases.
Amy Martin:The treehoppers that Rex studies the most are called
Amy Martin:thorn bugs, and they look like rose thorns that can walk. Other
Amy Martin:tree hoppers look like they have sand castles on their heads or
Amy Martin:bird droppings.
Amy Martin:Dr. Rex Cocroft: Others have what looks like a little
Amy Martin:Starship Enterprise in their back, a lot of interesting
Amy Martin:forms, and others, it's just a smooth roof.
Amy Martin:So treehoppers are kind of the quirky rock stars of
Amy Martin:the insect world pushing the boundaries of fashion and sound.
Amy Martin:This next one might be my favorite. Its scientific name is
Amy Martin:potnia brevicornis, but I think of it as Rage Against the
Amy Martin:Machine.
Amy Martin:Again, this hidden world of acoustic signaling is called the
Amy Martin:vibroscape, and I love that term, but it also made me
Amy Martin:wonder, since waves of vibration are happening anywhere there's
Amy Martin:sound, isn't the vibroscape sort of everywhere? I put the
Amy Martin:question to Rex.
Amy Martin:Is there a sharply defined line between a sound and a vibration?
Amy Martin:Because my understanding is that all sounds are vibrations. So
Amy Martin:why aren't all vibrations sounds?
Amy Martin:Dr. Rex Cocroft: They're very closely connected, and it
Amy Martin:depends on the sensory structures that you use to pick
Amy Martin:them up and how your nervous system then relays that
Amy Martin:information to your brain.
Amy Martin:We can experiment on ourselves in real time to
Amy Martin:understand this. If you're playing this episode through a
Amy Martin:speaker in your house or your car right now, and you crank up
Amy Martin:the volume, you might be able to feel the music vibrating the
Amy Martin:floor or the steering wheel. If you're a person who hears
Amy Martin:airborne sound, you can also hear those waves as they hit
Amy Martin:your eardrums. The waves of vibration have the same source,
Amy Martin:the music, but they can be perceived through two different
Amy Martin:sensory systems.
Amy Martin:Dr. Rex Cocroft: It's all the same thing. It's all mechanical
Amy Martin:energy that's propagating through an environment, whether
Amy Martin:it's a structure, whether it's the air, whether it's the water,
Amy Martin:but you have to have a different kind of sensor to pick it up. So
Amy Martin:for us, our vibration sensors are totally different from our
Amy Martin:ears and the information from those we feel it different. It
Amy Martin:goes to different parts of our brain, and so that's what makes
Amy Martin:it so different.
Amy Martin:For us.
Amy Martin:Dr. Rex Cocroft: For us, right. For us.
Amy Martin:Our experience of these two waves of vibration is
Amy Martin:bifurcated into two different sensory systems, hearing and
Amy Martin:touch, but that's just a reflection of the way our bodies
Amy Martin:happen to be put together.
Amy Martin:Dr. Rex Cocroft: For other animals, they may be just two
Amy Martin:sides of the same coin, like the ones that I study, these insects
Amy Martin:with their six legs, and they have vibration sensors in their
Amy Martin:legs, but some of those vibration sensors also act as
Amy Martin:pickups for airborne sound. And I don't honestly know how they
Amy Martin:tell the difference sometimes. How do they know if it's a sound
Amy Martin:or a vibration, if they're picking it up through their
Amy Martin:legs? And I'm not really sure the answer to that.
Amy Martin:Or maybe the whole question of what defines sound
Amy Martin:versus vibration only makes sense from within our own
Amy Martin:perceptual framework. Maybe if your senses of touch and hearing
Amy Martin:are more unified, there is no differentiation, really.
Amy Martin:Dame Evelyn Glennie: We're actually incredibly gifted
Amy Martin:listeners. You know that is inherent to being a human being.
Amy Martin:We have the capacity to listen. I think it's a categorization of
Amy Martin:the word "listen" that gets really confused.
Amy Martin:Dame Evelyn Glennie is a world renowned
Amy Martin:percussionist and composer. She's also deaf. She doesn't
Amy Martin:hear airborne sound waves, but she says listening is available
Amy Martin:to everyone.
Amy Martin:Dame Evelyn Glennie: You know, we think about hearing, and
Amy Martin:Evelyn grew up in rural northern Scotland, helping
Amy Martin:that's something that can be measured. That's something that,
Amy Martin:out on her family's farm, and she says the patience that
Amy Martin:you know, medically, we can see whether that person can hear a
Amy Martin:certain frequency at a certain volume. However, listening is
Amy Martin:farming requires gave her some of her first formative lessons
Amy Martin:not something that can be measured medically. Someone can
Amy Martin:be born deaf, but they can be amazing listeners.
Amy Martin:in listening.
Amy Martin:Dame Evelyn Glennie: Because listening is all about patience
Amy Martin:that I have learned over time. So you can't force a field to
Amy Martin:grow corn any quicker than it will grow the corn according to
Amy Martin:the season and the weather. You know, you can't dictate when a
Amy Martin:sheep will give birth to a lamb. It will just naturally give
Amy Martin:birth to a lamb as and when that time is right. You know, there
Amy Martin:are certain things that just need to happen naturally. And so
Amy Martin:I think that is very much to do with listening. You know, is
Amy Martin:that we can control a certain amount, but ultimately, we also
Amy Martin:have to work in partnership with the existence that we're in,
Amy Martin:with the environment that we're in.
Amy Martin:Evelyn had already exhibited a strong interest in
Amy Martin:and talent for music when she began to lose her hearing around
Amy Martin:the age of eight.
Amy Martin:Dame Evelyn Glennie: I realized that one aspect of the body was
Amy Martin:no longer working as it used to work.
Amy Martin:But this change did not stop her development as a
Amy Martin:musician. In fact, it seems to have enhanced it. When she began
Amy Martin:studying percussion at age 12, her teacher suggested she take
Amy Martin:out her hearing aids and tune into other ways of sensing the
Amy Martin:music. That's when she started to learn how to listen with her
Amy Martin:whole body, to pay attention to the vibe escape.
Amy Martin:Dame Evelyn Glennie: It's simply the knowledge that sound is
Amy Martin:vibration, that is what sound is, and therefore our bodies are
Amy Martin:a resonating chamber. So if I'm playing a glockenspiel or cymbal
Amy Martin:or triangle or anything with high frequencies, it's more than
Amy Martin:likely going to touch the face and the upper part of the body.
Amy Martin:However, with low, low sounds, such as playing bass drum or
Amy Martin:timpani, or anything with a really low, resonant sound.
Amy Martin:Obviously the vibration is quite wider and bigger, and that will
Amy Martin:reach a larger part of your lower part of the body. So you
Amy Martin:know, your tummy, your chest, down your legs, your feet,
Amy Martin:through the stage and so on.
Amy Martin:Evelyn has developed her ability to feel differences
Amy Martin:in pitch, tone and musical color at a much subtler level than
Amy Martin:most people, and used those skills to become one of the most
Amy Martin:celebrated percussionists of all time. She composes for the
Amy Martin:concert hall, for films and for television, and she performs all
Amy Martin:over the world. She's won multiple Grammy Awards, the
Amy Martin:Polar Prize, and a long list of other honors. Clearly, she has a
Amy Martin:musical force in her that was not going to be denied no matter
Amy Martin:what. But even though we're not all going to become musicians of
Amy Martin:Evelyn's caliber, she insists anyone can learn to sense sound
Amy Martin:as a whole body experience.
Amy Martin:Dame Evelyn Glennie: You know, the brain is an extraordinary
Amy Martin:thing, and it will re kind of jig itself in so many different
Amy Martin:ways. But it does need time. It really needs time.
Amy Martin:It also needs courage and freedom to explore,
Amy Martin:and Evelyn has cultivated those qualities in herself, along with
Amy Martin:a beautiful sense of play. Despite all of her success and
Amy Martin:expertise, she positions herself as a learner. She greets an
Amy Martin:instrument or a piece of music like she's greeting a friend.
Amy Martin:She doesn't assume anything. She asks questions, starts a
Amy Martin:conversation.
Amy Martin:Dame Evelyn Glennie: I'm very thankful just to have a curious
Amy Martin:take on things, and I think that's really what it boils down
Amy Martin:to. If I'm picking up a, let's say, a waterphone or something,
Amy Martin:you know, the first thing I'll do is look at the object. What
Amy Martin:is it made of? Is it metal? Is it wood? Is it skin? Is it
Amy Martin:ceramic? Is it glass? Is it porcelain? What is it?
Amy Martin:A waterphone looks like the mutant offspring of a
Amy Martin:pie pan and a hedgehog. It has a round base with spiky rods
Amy Martin:attached to it, which can be struck or bowed. The music
Amy Martin:you're hearing is from a video on Evelyn's YouTube channel
Amy Martin:called "Waterphone improvisation."
Amy Martin:Dame Evelyn Glennie: I look at the size of it. Is it hand held?
Amy Martin:Is it something that you have to sit to play? Is it something
Amy Martin:that you stand to play? Is it something that you use mallets
Amy Martin:to play or sticks to play and so on. So immediately, before I've
Amy Martin:even struck something, the whole body is involved. And how you
Amy Martin:can allow the body to be an extension of this object, so
Amy Martin:that there's no longer the player, the instrument, the
Amy Martin:audience, their music, the this, the that. So how is this body,
Amy Martin:sort of merging into this instrument? And then I'm like a
Amy Martin:kid, so I don't go on the internet and find out how to
Amy Martin:play the instrument. I just say, Evelyn, what are you going to do
Amy Martin:with this instrument?
Amy Martin:So there's no boundaries, no expectations, nothing.
Amy Martin:So we as sound creators are sound artists. You know, we're
Amy Martin:painting sound into a space.
Amy Martin:So you just sort of begin to think, oh, yeah, that's a fat
Amy Martin:sound, because it's felt through your tummy or your lower part.
Amy Martin:Oh, that's a much thinner sound, or that's a weak sound, or, oh,
Amy Martin:this is as far as I can go dynamically without maybe
Amy Martin:causing harm to the instrument. These are the different objects
Amy Martin:I can use. And bit by bit, you build up your kind of color
Amy Martin:palette. And so when you're looking at an instrument and
Amy Martin:engaging with that instrument, you're basically finding out all
Amy Martin:of the sign colors you possibly can in the environment that
Amy Martin:you're in that that particular instrument can produce through
Amy Martin:the imagination that you have and that you're willing to
Amy Martin:engage with.
Amy Martin:And that is that.
Amy Martin:Evelyn has become famous as a maker of sounds, but
Amy Martin:she says her primary purpose is to teach the world to listen. In
Amy Martin:fact, she created a foundation to advance that mission.
Amy Martin:Dame Evelyn Glennie: Listening is about being in the here and
Amy Martin:now. It's about living each day and taking the time to
Amy Martin:experience what is right in front of you. So it's kind of
Amy Martin:stripping down all of the complications, releasing all of
Amy Martin:the baggage that's on our shoulders, all of the
Amy Martin:expectations. It is just simply being and that's very
Amy Martin:liberating.
Amy Martin:I wanted to expand the boundaries of my own
Amy Martin:listening abilities and see if I could tap into the secret
Amy Martin:treehopper communication channel that Rex had told me about. So I
Amy Martin:bought a small contact microphone and attached it to
Amy Martin:some plants, a lot of plants, and mostly I heard wind and
Amy Martin:plant stems bumping into each other. But I got better with
Amy Martin:practice, and one day in a park in Iowa City, the magic
Amy Martin:happened.
Amy Martin:I couldn't see who was making this noise or where it was, but
Amy Martin:somebody was talking and kind of humming. I sent this recording
Amy Martin:to Rex Cocroft, and he said it was definitely something in the
Amy Martin:cicada group, probably a leafhopper, but he couldn't say
Amy Martin:for sure which one. He said it wasn't a sound he had recorded,
Amy Martin:and chances were no one else had heard or recorded it either,
Amy Martin:which felt pretty extraordinary. It's not very often that I can
Amy Martin:say I might have recorded a sound that no other human has
Amy Martin:ever heard, and now you've heard it too.
Amy Martin:We don't know what it's like to be a treehopper hearing or hear
Amy Martin:feeling the call of another treehopper through a plant. Just
Amy Martin:like with the dolphins, we can't get inside their experience. We
Amy Martin:can get closer to guessing what our fellow humans are
Amy Martin:experiencing, but even then, we can't really know. Some people
Amy Martin:feel vibrations very sensitively. Other people hear a
Amy Martin:huge range of airborne sound, or none at all, and whatever we're
Amy Martin:hearing and feeling right now, that experience is bound to
Amy Martin:change over time, often in ways we can't control. Sound is
Amy Martin:ephemeral and ever changing, and so is our experience of it. So
Amy Martin:you know that Christmas carol that asks, do you hear what I
Amy Martin:hear? Well, now I know that the answer is probably, no, I don't.
Amy Martin:Or maybe kind of sometimes? but that difference is actually what
Amy Martin:connects us. No one person or even one species can hear
Amy Martin:everything, but together, we are a planetary ensemble of
Amy Martin:listeners, each of us making our own entirely unique
Amy Martin:contributions, the treehoppers and the spiders, the dolphins
Amy Martin:and the percussionists, the corals and the fishes and you
Amy Martin:and me.
Amy Martin:This episode of Threshold was written, reported and produced
Amy Martin:by me, Amy Martin, with help from Erika Janik and Sam Moore.
Amy Martin:Music by Todd Sickafoose, post production by Alan Douches. Fact
Amy Martin:checking by Sam Moore. Special thanks to Stephanie King for
Amy Martin:some of the dolphin sounds you heard in this episode, to Rex
Amy Martin:Cocroft for the use of his treehopper recordings, and to
Amy Martin:Evelyn Glennie for the use of her music. I highly recommend
Amy Martin:that you check out Evelyn's YouTube channel and watch her do
Amy Martin:the waterphone improvisation we played or any of her other
Amy Martin:videos there. Just search for Dame Evelyn Glennie on YouTube,
Amy Martin:or you can find a link on our website or in the show notes.
Amy Martin:Threshold is made by Auricle Productions, a non profit
Amy Martin:organization powered by listener donations. Deneen Weiske is our
Amy Martin:Executive Director. Learn more at thresholdpodcast.org.
