Explorers

“Durn it, this SHOULD work!”

Well, what can you say? Sometimes your science experiments just don’t turn out the way you expect them to, no matter HOW stubbornly you pursue them.

The theory and science behind this activity are fairly simple. The Explorers investigated the nature of sound waves earlier in the year (“Making Waves”), and now sound was again the topic. Sound waves, of course, are disturbances or vibrations in the air (or another medium) that our ears collect and our brains then interpret as noises. Put in the simplest terms, our ears are really just sound funnels. Animals with larger or differently shaped ears have more acute hearing than us—they can hear softer sounds than humans can.

The first question Mr. Ramsey posed to the group was why, though, do we need TWO ears? This is actually related to the reason having two eyes is an advantage—in both cases the spacing between the pair has a purpose. For our eyes it helps with our depth perception. Closing one eye makes it much more difficult to judge how far away various objects are, especially compared with one another.

With our ears, having a pair is crucial to pinpointing the direction of a sound. The key to this is that unlike light, sound travels at a speed that we can actually perceive. (Light also has a certain speed, but it is so fast that it is impossible for us to perceive it under normal conditions.) Sound travels about 1000 feet per second—pretty fast, but not beyond our perception. The best example of this is thunder and lightning: when you see a flash of lightning, start counting. For every five seconds that passes until you hear the thunder, the lightning happened about one mile away.

So what does this have to do with our two ears? Suppose someone claps from across the room directly to your left. The sound from the clap reaches your left ear a tiny split second before it gets to your right ear—a very small difference in time, to be sure, but enough that your brain can tell the difference. You may not actually be conscious of detecting the difference in arrival times between your two ears, but your brain does so whether or not you are aware of it. Lose the hearing in one ear, and it becomes much more difficult to tell what direction a sound is coming from.

The Explorers checked this out for themselves. As Mr. Ramsey moved around the room talking, the students followed his every movement unerringly—with their eyes closed.

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Now it was time to see if we could do two things: first, enhance our hearing; and second, fool it. For both activities the students needed to assemble a special set of “headphones.” To do this, they started with large sheets of construction paper that were rolled into cone shapes. The narrowest ends of these were taped to lengths of plastic tubing. The other end of each piece of tubing was inserted and taped into one side of a set of headphones that Mr. Ramsey had already drilled holes into. When each assembly was all put together, the students had a set of headphones with paper cones connected with plastic tubing to each side.

In theory, now, the students had enhanced sound collectors—bigger ears, to put it another way. Just as an elephant’s hearing is more sensitive due to its larger ears, the students should now have more sensitive hearing with their own larger ears. This was tested by pairing the students and blindfolding one at a time. Did it work? Well, not really, probably in no small part because the paper cones were terribly flimsy—not only did they keep crumbling and not holding their shape, they also did a lousy job of bouncing the sound waves into the tubing and headphones.

Time was up for the first activity (following a cupcake treat to celebrate one of the Explorer’s birthdays). In the time before the next meeting, Mr. Ramsey and Lissa (the trusty club assistant) came up with a Plan B. They ditched the paper cones and replaced them with plastic funnels, in the hope that the sturdier material would do a better job of collecting the sound waves.

Did the funnels do the trick? Umm, sort of. They were definitely an improvement over the construction paper, especially in holding together. Again the students got paired up, taking turns being blindfolded. We again tested our sensitivity and ability to pinpoint sound direction, but this time we also tried “fooling” our hearing. This was done by having the partner reverse the sides of the funnels, so that the sounds going in the left-hand side were actually funneled into the right ear and vice versa. The idea was that this would trick the brain into thinking that the sounds it was hearing were arriving from the opposite direction of where they actually originated.

This worked reasonably well from close up, as the partner (or Mr. Ramsey) spoke nearby or whispered directly into one of the funnels. From a distance, though, the students’ ears were not as easily fooled, although they were generally more hesitant about picking the correct direction. Perhaps with louder sounds at a distance, the headphones were loose enough on the students’ heads that their ears were also picking up the sound waves directly under the headphones, not just through the funnels and the tubing.

In any case, it was a fun activity, and it never hurts to demonstrate that science experiments are under no obligation to go the way you plan. Not to mention that having the kids wear the blindfolds and the headphone/funnel contraptions made for some interesting photos!

To see some pictures from our two sound activity sessions, check out the Gallery.