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Explorit: Try this experiment to hear astounding sounds

By From page A7 | February 28, 2014

You hear a sound in the distance and turn your head. Where did it come from? And how did it get from its source to your ears? It’s invisible, after all. Here’s an activity to try at home that just might help you figure it out.

You will need a pair of scissors, some string, a wire coat hanger, a ruler or measuring tape and a table, a wall or a door. Start out by cutting a piece of string about three feet long. Adults should cut a piece about four feet long.

Hold the two ends of the string in one hand so that the rest hangs down and makes a loop. Lay the loop over the hook part of the hanger. Push the two ends through the loop and pull them all the way through to the other side. (This is easier to undo than a knot.)

Wrap the loose ends of the string two or three times around the first fingers on each of your hands. Now swing the hanger so that it gently bumps against the leg of a table or against a door. Did you hear anything? What did it sound like?

Next, put your hands over the openings of your ears. Hold your hands tight to the sides of your head. Lean over and gently bump the hanger again. What does it sound like this time? Is it the same sound as the first time or different?

When the hanger bumps against something, it causes the string to vibrate. The vibrations travel to your hands and then through the bone of your skull directly to the fluid inside your inner ear. In the fluid, cells with tiny sensing hairs transform the vibrations into electrical signals that then travel along the auditory nerve to your brain.

When your hands weren’t covering your ears, the sound was much fainter. The hanger made the same sound in both situations, but in one you provided a path that let more of the sound reach your ears.

Try the experiment again with other kitchen utensils — a metal spoon or fork, a cake rack, etc. What sounds do they make? What might account for the differences in the way the items sound?

Or try some non-metal objects like a pencil or wooden spoon. Do they sound the same as metal ones or different? Why? Also try gently bumping your sound objects against other surfaces like a fabric-covered couch or metal doorknob. Which surfaces make the best sounds?

You can experiment more with the science and art of sound at Explorit’s “Beautiful World: Science and Art” exhibition, open Wednesdays, Saturdays and Sundays from 1 to 5 p.m. and Fridays from 3 to 6 p.m.

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Explorit’s coming events:

* Explorit’s “Beautiful World: Science and Art” exhibition is open to the public every Wednesday, Saturday and Sunday from 1 to 5 p.m. and every Friday from 3 to 6 p.m. at 3141 Fifth St. Admission is $5 per person; Explorit members, teachers and children 2 and under are free.
* Afterschool Science Adventures for students in kindergarten through sixth grade begin Wednesday afternoons at Explorit in March. Call Explorit at 530-756-0191 for more information or to register.
* Birthday parties are back at Explorit: Call Explorit at 530-756-0191 for more information or to book your party.
* Summer Science Camp is coming: Registration opens Monday, March 17. Camp titles, a full schedule and all the details are coming soon to www.explorit.org.
* NanoDays is coming to Explorit for spring break March 24-28. Save the dates!

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Explorit Science Center is at 3141 Fifth St. For more information, call 530-756-0191, visit www.explorit.org or “like” Explorit on Facebook at www.facebook.com/explorit.fb.

Lisa Justice

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