Science Diary: Volcano - Array: The Pulse of the Planet daily radio program offers free legal online mp3 downloads, exploring the world of sound in nature, culture and science, with audio adventures, world music, extraordinary sound portraits, science diaries, and nature ring-tones; an amazing sonic experience.



Airdate: Jul 08, 2008
Scientist: Milton Garces, Ph.D.

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 EARTH SCIENCE ,Volcanoes ,Acoustics ,sound


Science Diary: Volcano - Array

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Our ears are not the best tools for eavesdropping on a volcano's sonic secrets; that's where microphone arrays come in handy.
Transcript:

music; ambience volcano

Whenever you go service an instrument near a volcano, you put yourself at substantial risk, because it can erupt, or there can be an excess of corrosive gasses around it.

Milton Garces is a researcher at the University of Hawaii who studies volcanoes. And in order to avoid the dangers of getting blasted or burnt, he records them from a distance. Welcome to Pulse of the Planets Science Diaries, a glimpse of the world of science from the inside. Up to now, weve been listening to explosions recorded at Stromboli volcano. But volcanoes also produce sounds we cant hear infrasounds, vibrations so so low in frequency, theyre actually below the range of human hearing. We have to speed up infrasonic recordings to hear them. Like this.

ambience: volcanic infrasounds sped up

With infrasound, we try to capture sounds that are below the hearing threshold of the human ear. Although we cannot hear infrasounds, we can perceive it. If you are standing close to an open volcanic vent, you will actually feel in your bones low frequency vibration as it passes through you.

Milton Garces operates three infrasound arrays on Hawaiis Big Island. These arrays are clusters of microphones placed miles away from the volcanos danger zone. But greater distance introduces additional sounds: an ocean surf, shipping lanes, and nearby cities.

We use a carefully positioned cluster of microphones to create an infrasound array. The arrays help us distinguish the sounds from the volcano, from the ambient sound field that exists at every site.

To learn more about Milton Garces research, check out his blog on pulseplanet.com.

Pulse of the Planets Science Diaries are made possible by the National Science Foundation. Im Jim Metzner.







 
Science Diary: Volcano - Array