Close Listening: How Sound Reveals The Invisible
Over the years, scientists have mostly interpreted the world through what they can see. But in the past few decades, a culture of listening has blossomed, especially among biologists who seek to understand how animals communicate. This week Morning Edition embarks on a weekly summer series called Close Listening: Decoding Nature Through Sound. We begin with an innovation that transformed medicine by searching sounds for clues to illness and health.
Microscopes illuminate the invisibly tiny; telescopes reveal the heavens. But sound? Scientists didn't really see it as all that important, until an amazing invention came along that opened new worlds: the stethoscope.
"I think the first time one can see this kind of 'listening culture' is with the development of the stethoscope at the beginning of the 19th century in Paris," says Trevor Pinch, a Cornell University sociologist.
"You couldn't see inside a body back then," Pinch says, "unless of course it was dead, which was a bit late for anyone except a pathologist." But a stethoscope told a living story — of circulating blood, or the seesawing of lungs.
"It was one of the first ways of getting a diagnosis on a patient independent of their own version of what was happening," says Pinch. "In fact, it's become so important that the emblem of the physician is often the stethoscope around the neck — that's how you tell who the doc is."
We asked one of those doctors to help us hear the way he hears. Dr. Adam Law, an endocrinologist and primary care physician in Ithaca, N.Y., was teaching a medical student how to use a stethoscope to diagnose a heart problem in one of his patients, and we brought along recording equipment so we could listen in. Law's student is Nick Maston, in his third year at Weill Cornell Medical College.
Law ushered the patient into the examining room, and turned to his student. "Nick, why don't you examine this patient's cardiovascular system?" We'd already plugged our recorder into the electronic stethoscope, but Law and Maston both warned us — interpreting sounds from inside a body is not for amateurs.
"As a student," said Maston, "it's hard to learn ... you have to listen to thousands of hearts to find that out."
Maston placed the bell of the instrument on the patient's neck — right on the carotid artery — and we all heard this:
It's the sound of the heart pumping blood through its aortic valve and out into the pulsing carotid artery. Then Maston moved the bell to the patient's side, placing it just under the man's armpit. A slightly different sound came through:
Law turned to his student: "Hear the difference in quality?" Maston didn't hesitate: "Yeah; very loud second heart sound."
Law's patient has a heart murmur — a malfunction of the heart valves that control blood flow. Textbooks say you can hear a murmur's "swishing" sound. But if you didn't hear it, don't feel bad — we journalists couldn't make out any swishing sound, either.
Maston apparently could. "So, do you want me to talk about what I heard?" he asked us. "It sounded like a mitral murmur; but I heard it best where I expect to hear an aortic murmur. So ... this is a situation where Dr. Law is going to have to jump in and rescue me."
Law confirmed that Nick had it right. The patient's heart has a little bit of both types of murmur, he said, from the mitral and aortic valves.
We amateurs didn't hear it because we simply didn't know what to listen for. Think of the sound as if it were the audio version of a fossil bone or relic lying in the dirt; a seasoned archaeologist can pick those out more readily than other people because the pros have a sort of "search image" in their brain.
"The musical note of the heart is actually complicated," Law said. "It has harmonics; it has overtones. And that gives the sound — and the murmurs — in the heart a certain quality," he explained. "One has to tune one's ears."
So how do you tune your ears? "Pattern recognition is the key," Pinch told us later.
Some patterns, like the start of Beethoven's Fifth Symphony, are easy:
Easily recognized. But it gets harder as the sounds get more complex. Two moustached wrens singing a duet start as two seemingly random singers. Then they suddenly synchronize their songs, and a pattern emerges:
Pinch has made a career of studying how scientists listen. He notes that listening has certain advantages over vision. "The visual field is kind of in front of us — like a kind of screen," he says, while sound is "all around."
If seeing is like being in an art gallery, hearing is more like being in a swimming pool — where we're swimming all the time. At night, we'll wake up to a baby's cry, or to the sound of danger — a predator, perhaps. Such sounds trigger an ancient alarm system buried deep within our species' brains. Listening, says Pinch, especially at night, "has probably been evolutionarily very, very important."
The problem of using sound to understand physical phenomena — from the weather to animal behavior, to the fact that an engine needs oil — is that sound is ephemeral. It's in one ear and out the other.
An advertisement for Edison's phonograph circa 1900.
That is, until, as Pinch points out, people invented a way to nail down sound. "I think the development of the phonograph, in particular, around 1880 ... really does change how we think about sound," Pinch says. "Because, for the first time ever, sound is really transportable. ... You can store it in a medium."
Once people could capture sound, and really listen, Pinch says, that opened up a universe of new possibilities.
Editor's note: An alert reader reminds us that heart murmurs can arise from other sources, too, and that many such sounds are harmless.
Bill McQuay is an audio producer at the Cornell Lab of Ornithology.
He's on Twitter: @mcquay_bill. Alison Richards, NPR's Senior Editor for science, is the series' editor.
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Transcript
RENEE MONTAGNE, HOST:
Most of the creatures we share the planet with have stories to tell. But you have to know how to listen. MORNING EDITION is going to explain how with our project on Close Listening - Decoding Nature Through Sound. NPR science correspondent Christopher Joyce and audio producer Bill McQuay of the Cornell Lab of Ornithology start us out today with a look at how scientists started learning to listen.
CHRISTOPHER JOYCE, BYLINE: The natural world is noisy...
(SOUNDBITE OF MONKEYS HOWLING)
JOYCE: ...With howler monkeys...
(SOUNDBITE OF WHALE VOCALIZATIONS)
JOYCE: ...Whales in the ocean deep or insects in a backyard tree.
(SOUNDBITE OF INSECTS CHIRPING)
JOYCE: Bill McQuay and I recorded a lot of the natural world for an NPR program called Radio Expeditions.
BILL MCQUAY: That audio is archived at the Cornell Lab of Ornithology, where I work now, in a room stacked with shelves of reel-to-reel tapes and cassettes.
JOYCE: It's the world's largest collection of natural sounds. And Bill and I got to wondering, who captured all that sound and what did they learn from it? So I went to see the collection.
Collection storage room 132.
(SOUNDBITE OF DOOR OPENING)
JOYCE: Let's go exploring.
MCQUAY: Yeah.
JOYCE: What do you call these things?
MCQUAY: A space saver movable shelf.
JOYCE: Do you have any idea how many recordings are here?
MCQUAY: Hundreds of thousands.
JOYCE: There's a lot here. Elephant seals, I remember that.
(SOUNDBITE OF ELEPHANT SEALS BARKING)
JOYCE: This was elephant seals on the coast of California, where they'd pull up onto the beach and basically lie around and make a lot of noise.
(SOUNDBITE OF ELEPHANT SEALS BARKING)
MCQUAY: The sounds that every 10-year-old would love to make.
JOYCE: (Laughter).
(SOUNDBITE OF ELEPHANT SEALS BARKING)
JOYCE: What else do we have? What about the elephant bai in the Central African Republic? There it is.
MCQUAY: That would be up here.
JOYCE: That's one you were on.
MCQUAY: That's right.
(SOUNDBITE OF ELEPHANTS TRUMPETING)
MCQUAY: The sound was the best way to develop a census of how many elephants were in the area because forest elephants, as large as the elephant may be, once it's in the rain forest, you don't see them.
JOYCE: You don't see them. Yeah, you can't see them.
(SOUNDBITE OF ELEPHANTS TRUMPETING)
JOYCE: We realized that this sound tells a story about how science learned to listen. Seeing used to be everything. Microscopes illuminated the invisibly tiny. Telescopes revealed the heavens - but sound, not important until an amazing invention came along.
TREVOR PINCH: The first time that one could see this kind of listening culture developing is with the development of the stethoscopes in the beginning of the 19th century in Paris.
MCQUAY: Professor Trevor Pinch teaches the history of science and technology at Cornell University. He reminds us that you couldn't see inside a body back then.
JOYCE: Unless it was dead.
MCQUAY: Yeah, but that was too late. A stethoscope told a living story of circulating blood or the seesawing of lungs.
PINCH: It was one of the first ways of actually getting a diagnosis on a patient independent of their own version of what was happening. In fact, it's become so important it's kind of - the emblem of the physician is often the stethoscope around the neck. That's how you tell who the doc is (laughter).
MCQUAY: I found one of those doctors in Ithaca, N.Y. He was teaching a medical student how to use a stethoscope to diagnose a heart problem in one of his patients.
JOYCE: We joined them in the doctor's examining room.
ADAM LAW: I'm Adam Law. I'm a physician. I'm both a primary care physician and an endocrinologist.
NICK MASTON: I'm Nick Maston. I'm a third-year medical student.
LAW: OK, so why don't we bring you into the examination room?
Nick, why don't you examine this patient's cardiovascular system?
MASTON: All right.
MCQUAY: Nick has an electronic stethoscope that I plug into my recorder.
JOYCE: So that we can listen too. But they've warned us, interpreting sounds from inside the body is not for amateurs.
MASTON: As a student, it's hard to learn. It takes listening to hundreds - thousands of hearts before you start to figure that out.
MCQUAY: Nick places the bell of the instrument on the patient's neck, right on the carotid artery.
(SOUNDBITE OF HEARTBEAT)
MCQUAY: We could hear the sound of the heart pumping blood through its aortic valve and out into the pulsing carotid artery.
LAW: So this is the second position here.
MCQUAY: Nick moves the bell to the patient's side, placing it just under the armpit.
(SOUNDBITE OF HEARTBEAT)
LAW: Hear the difference in quality?
MASTON: Yeah.
LAW: Yeah. I hear a very loud second heart sound.
JOYCE: The patient has a heart murmur, a malfunction of the heart valves that control blood flow. Textbooks say you can hear a murmur's swishing sound.
MCQUAY: But I sure couldn't hear any swishing sound.
JOYCE: Yeah, neither could I, but Nick apparently did.
MASTON: So do you want me to talk about what I heard?
LAW: Yes, what did you hear?
MASTON: It sounded like a mitral murmur, but I heard it best where I would expect to hear an aortic murmur. So this is a situation where Dr. Law's going to have to jump and rescue me.
LAW: He has a little bit of both. We've learned that you can have - sometimes have two different murmurs in the same heart.
JOYCE: Dr. Law said Bill and I simply didn't know what to listen for.
LAW: The musical note of the heart is actually complicated. It has harmonics, and it has overtones. And that gives the sounds and the murmurs that you hear within the heart a certain quality. And one has to tune in one's ears.
MCQUAY: So how do you tune your ears? We asked Trevor Pinch, the history professor.
PINCH: So pattern recognition is the key.
(SOUNDBITE OF ALEXANDER TITOV SONG, "ALLEGRO CON BRIO")
JOYCE: Yes, that pattern is easy.
MCQUAY: But many are not.
(SOUNDBITE OF MOUSTACHED WRENS)
MCQUAY: Take birdsong. This is a recording of two moustached wrens.
(SOUNDBITE OF MOUSTACHED WRENS)
MCQUAY: The scene appears random until the birds synchronize and a pattern emerges.
(SOUNDBITE OF MOUSTACHED WRENS)
JOYCE: Patterns tell us things, like how birds collaborate.
MCQUAY: Then there's the fact that sound is everywhere.
PINCH: The visual field's kind of in front of us. It's like a kind of screen. And sound is all around.
JOYCE: Seeing is an art gallery. Hearing is a swimming pool.
MCQUAY: And we're swimming all the time. At night, we'll wake up to a baby's cry or to the sound of danger.
(SOUNDBITE OF LION ROARING)
PINCH: And it's probably been evolutionarily very, very important how we become attuned to sound at night.
JOYCE: So OK, interpreting sound has survival value. But to really study it, well, that was a problem.
MCQUAY: In one ear and out the other.
JOYCE: Ephemeral.
MCQUAY: Until another revolutionary invention.
PINCH: I think that the development of the phonograph in particular around 1880 - that really does change how we think about sound because for the first time ever, sound is really transportable. You can store it in a medium.
(SOUNDBITE OF WHALE VOCALIZATIONS)
MCQUAY: When people could capture sound and really listen.
(SOUNDBITE OF WHALE VOCALIZATIONS)
JOYCE: That opened up a whole new world.
(SOUNDBITE OF WHALE VOCALIZATIONS)
JOYCE: That's our next story.
I'm Christopher Joyce, NPR News.
MCQUAY: And I'm Bill McQuay.
(SOUNDBITE OF WHALE VOCALIZATIONS) Transcript provided by NPR, Copyright NPR.
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