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Article for: The Davis Enterprise
Date: July 11, 2003
Author: Tom Wickersham
Contact: Tom Wickersham

SOUND OFF AT EXPLORIT

Explorit's current exhibit examines patterns and numbers found in the natural world. Most are easy to see with the naked eye, but what about patterns in sound?

Visitors to Explorit can delve into the math and geometry of such things as human growth, crystal shapes and magnetic fields in the exhibit "Count on It: Numbers in Nature." Children and adults are often surprised at the sheer volume of patterns - both in numbers and in shapes - that are in our world.

Honeycombs use hexagons, temperature is measured with mercury, and the age of a deer can be identified by examining its teeth. (You might not be able to do this in nature, but the teeth on the jawbones at Explorit are a bit easier to count!)

The sound of our voices can be quantified as well. With the help of an oscilloscope, visitors can sing, whistle or play an instrument and can see the resulting sound waves.

What is a wave? Essentially, waves are energy vibrations that travel through some medium such as air or water. When a wave travels through a medium, only the energy itself moves. The particles of the medium are not permanently displaced. (Light, however, can travel through a vacuum and does not need a medium for propagation.)

Sound waves travel at different speeds through different media. Sound travels slowest through gases (like air), faster through liquids (like water) and fastest through solids. The denser the medium, the faster sound travels.

Every passing wave can be described as regular rises and falls of energy. We measure these rises and falls in terms of wavelength, frequency and amplitude. Frequency is the number of wavelengths that pass a given point per second, and is measured in hertz (Hz), after Heinrich Hertz, a German scientist who discovered radio waves.

Humans typically hear sounds between 20 and 20,000 Hz. Some of the most intense frequencies of an earthquake produce sound well below our hearing range, much of it below 1 Hz. The sounds of a dog whistle fall above the human hearing range at 30,000 Hz.

Sound pitched higher than humans can hear is called ultrasound. Some animals depend on ultrasound. Bats, for example, use ultrasound to "see" in absolute darkness. They make ultrasonic squeaks - around 120,000 Hz - as they travel in darkness.

Although visitors won't be able to make ultrasounds themselves, they will be able to compare sound waves by using different tuning forks or by singing at different pitches. Who knows? You might find yourself headed towards a lucrative musical career as you investigate the sound waves of your voice.


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Explorit Science Center is at 3141 5th Street in East Davis. The current exhibition is "Count on It: Numbers in Nature," which continues through Sept. 27. Public hours are Saturday from 11 a.m. to 4:30 p.m., Sunday from 1 to 4:30 p.m., and Tuesday through Friday from 2 to 4:30 p.m. For more information, visit www.explorit.org or call Explorit at (530) 756-0191.