Objective – Describe the production of sound in terms of vibration of objects that create vibrations in other
materials.
Sounds – Sound Analysis
Our ears are giving us clues to our surroundings - Are you listening?
JM: If you walk into a room with your eyes closed can you figure out where you are
just by listening? I'm Jim Metzner and this is the Pulse of the Planet. Our ears are
actually finely-tuned instruments, working with the brain to sort and analyze the
sounds all around us.
BH: I've always been amazed at how much information is in sound that we don't tune
into in the same way that we tune into visual information. Sound, it's much more
impressionistic.
JM: Bart Hopkin is an experimental musician in Point Reyes, California and one of the
scientists and engineers in this year's Kid Science Challenge, our free nationwide
competition. He's spent his career building musical instruments out of everyday
objects, making use of our ears' extraordinary ability to discriminate sounds.
BH: It's amazing how much sound information we process without thinking about it.
And so, first of all, you could say, “How did I know somebody was at the door? Oh. I
guess I heard them walking up the steps.” That's one level, but another level you could
say is, “What information about the oscillations in the air that reach my ears even
made me know that that was somebody coming up the steps?”
JM: So if you hear the high-pitched click of high heels, you may just know who's
walking down the hall. Or when you listen to the sound of my voice you know I'm
inside a room, not outside on a mountaintop.
BH: That as I speak, the sound is reflecting off of other interior surfaces and there are
things about how long those reflections take. Do they arrive almost immediately, or do
they take a while to arrive? That tells you a little bit about how big or how small the
room is. Do they favor high frequencies or low frequencies? That tells you a lot about
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Objective – Describe the production of sound in terms of vibration of objects that create vibrations in other
materials.
whether you're in a room with a lot of people or a lot of soft furniture versus a room
that is cavernous with hard walls.
BH: We do some pretty serious analysis.
JM: In this year's Kid Science Challenge, we're inviting 3rd to 6th graders to do some
sound analysis of their own by coming up with an idea for a new musical instrument.
Check out Kid Science Challenge.com. Pulse of the Planet is made possible by the
National Science Foundation.
Ants & Caterpillars: Sound
Sound - and sweet excretions - are ingredients for harmonious behavior between ants and caterpillars.
Caterpillars talking with ants? Sounds like a Disney cartoon, but in Arizona's Sonora
Desert, these two insects really do communicate with each other. I'm Jim Metzner, and
this is the Pulse of the Planet. In a moment we'll hear the sounds of caterpillars, but
let's first set the scene. With the advent of the summer monsoon rains, the Sonora
Desert comes alive. Acacia shrubs are in bloom, and their nectars and flowers attract
both ants and butterflies. The butterflies lay their eggs and when the young caterpillars
hatch, they come under the care of the ants. The ants feed off the nutritious secretions
of the caterpillars and in return defend the caterpillars from predators. It turns out
there are a number of ways that the caterpillars have found to communicate with, and
influence the behavior of the ants. Diane Wagner is an assistant professor in the
department of Biological Sciences at the University of Nevada in Las Vegas.
“Well, the caterpillars have various ways of communicating with the ants. Some are
chemical, some are tactile, we think, some are through sound. The caterpillars have
pores all over their bodies, and we think they secrete some substance that tells the ants
that they're not prey. They have these hair-like glands that they extrude when they're
alarmed, and those seem to get the ants riled up as well. So that may be a way for the
caterpillar to chemically manipulate the ants' behavior. And now recently, people
started paying attention to sound production in these caterpillars. We think that their
signals, that they help the ant localize the caterpillar on the tree. So, the sound is very
soft, and we can hear it if we amplify it.”
Pulse of the Planet is presented by the National Science Foundation. I'm Jim Metzner.
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Objective – Describe the production of sound in terms of vibration of objects that create vibrations in other
materials.
Dwarf Minke Whales-Star Wars Sound
For fifty years, these underwater sounds were an unsolved mystery.
The sounds we're listening to were recorded underwater off the coast of Australia. And
although similar sounds have been heard in the world's oceans for many years, their
identity was unknown until fair recently. I'm Jim Metzner, and this is the Pulse of the
Planet.
“People have recorded their sounds for about 50 or so years. They're described as the
boing, the Boing Fish, the Guitar Fish, the razor, and these were all because people
didn’t know what produced these sounds. When we first recorded it on the Great
Barrier Reef, we called it the Star Wars sound because it sounded like a ray gun out of
a Star Wars movie.”
Jason Gedamke is a Graduate student at the University of California in Santa Cruz. He
thought that the sounds were produced by a species of whale.
“I sent my recordings to some experts in the field of whale acoustics. And one of the
people that responded to me actually sent back the sound, he said 'thank you for your
very interesting sounds. But I don’t believe that anything biological could have
produced them.' And he actually told me to take a look and see if the Australian navy
was running some type of operations in the area.”
Jason Gedamke was ultimately able to show that these sounds were in fact made by a
Dwarf Minke Whale.
“It actually took a very long time to bed able to prove that these sounds do come from
the Minke Whale. Because they are so unusual there was a lot of skepticism out there.
And what we did was essentially locate where a sound was being produced over many,
many hours and hours and many, many different field seasons. We would locate the
sound and look in the area for whales, and we were able to, on hundreds of occasions
at this point, locate sounds and then visually verify that there were whales within
meters of where we located the sounds.”
We'll hear more on Minke Whales in future programs. Pulse of the Planet is presented
by the National Science Foundation. I'm Jim Metzner.
~3~
Objective – Describe the production of sound in terms of vibration of objects that create vibrations in other
materials.
BATS--Use of Sound
Which kinds of bat sounds are used for communication, and which allow them to detect their
surroundings?
We're listening to the sounds of a colony of Mexican Free Tailed bats getting ready for
their nightly flight in search of insects to feed on. Bats use a broad spectrum of sound
to communicate and to find their way. I'm Jim Metzner, and this is the Pulse of the
Planet, presented by the American Museum of Natural History.
We have no idea what the bats are saying, but they're probably holding conversations
not that dissimilar from some we hold: 'Ouch you’re getting too close!' 'I'm sleepy
leave me alone.'“
Merlin Tuttle is the Director and Founder of Bat Conservation International. He tells
us that although it's not known exactly what the bats are saying to each other, it seems
clear that they share information about food sources.
“We know very little about communication in bats, but it's obvious that they do
communicate because they may travel for two or three weeks in a row, exclusively in
one direction and then all of a sudden one night, hundreds of thousands take off in an
entirely new direction. Obviously somebody told them about good dining.”
Bats also produce sounds that human ears can't hear--- high pitched echolocation
signals which enable them to detect objects in their environment.
“Each one of these bats as it flies over is producing about 10 beeps of sound every
second. We call that echolocation. As it detects a moth or another insect to capture, it
then speeds that rate up to about 200 beeps per second. We believe that most bats use
ultrasound primarily to navigate and locate prey and lower frequency sounds to
communicate amongst themselves. But that's simply a scientist's belief. We could be
very wrong.”
Pulse of the Planet is presented by the American Museum of Natural History.
Additional funding for this series has been provided by the National Science
Foundation. I'm Jim Metzner.
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