Thursday, January 15, 2009

Things We Can't Hear

How long have humans and elephants shared the same geographical spaces? But it wasn't until 1984 that someone finally noticed that there were strange vibrations coming from the elephant cage at a zoo. As it turns out, elephants use infrasonic sounds (sounds lower than the deepest bass note we can hear) to communicate. Researchers have since identified around 300 distinct infrasonic calls that elephants make to each other. Their massive bodies provide the resonance to generate such low frequencies, and these sounds can travel many miles through the earth. Elephants can detect these sounds through the sensitive pads on their feet.

It's also known that another set of massive animals, whales, also use infrasounds to communicate. Their deep sounds, inaudible to us, can travel across an entire ocean in an hour. Not only do they use their ability to hear at these low-frequencies to communicate, but to locate food. Then along comes the US Navy with sonar that uses the same type of sounds. But the Navy sonar emits sounds at 235 decibels--equivalent to the noise from a space shuttle launch! Sounds this loud are not merely noise pollution for the whales, they are unbearable and can even be deadly. Ever wonder why you hear reports of whales beaching themselves? Omitted from the reports is the fact that they are often bleeding from their ears and eyes. They beach themselves to get out of the water that is carrying sounds that torture them, sometimes literally to death.

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