Whether you're talking about the lousy acoustics in your school cafeteria or the reason why the siren sounds different once it's passed you, sound waves are the scientific phenomenon behind the terrible gurgling that the principal makes over the microphone.
No matter whether you're in elementary or middle school, there is an experiment out there to help you grasp the concept of sound waves and perform an experiment that may get you an award — or at least some extra credit.
Sound and the Environment: Noise Pollution
Along with light pollution, noise pollution is one of the most insidious forms of environmental decay out there. While noise pollution doesn't shred the ozone layer, it does inconvenience our neighbors (the furry ones as well as the ones in the neighboring homes). That stereo system that you installed in your outdoor patio can keep you awake — and your neighbors too. By measuring the sound levels coming from several different sources, you can determine which would be the noisiest items to have in and around your yard — and what places would be the noisiest to live.
Any noise source that is annoying, loud and potentially damaging to your ear can be considered noise pollution. Sudden loud sounds, or prolonged exposure to loud sounds, can cause damage inside the year; our addiction to texting and talking loudly means that we are a significant source of noise pollution ourselves.
For this experiment, you'll need a decibel meter to measure the levels of different sounds. If you measure a whisper, you'll get between 20 and 30 dB. Normal conversational levels range around 60. If someone's shouting at you, bump that number up to 80.
Hypothesize about the loudest places you'll see. The school gym during a pep rally? Walking by that city employee using a jackhammer on your street? Carry the decibel meter with you. Measure the levels at different places and make a chart. Evaluate the relative quality of your hypothesis — how many of your guesses were correct?
The Best Soundproofing Materials
So, you want to soundproof your closet, or maybe even your whole bedroom, so you can play your music as loudly as you want to, without your parents popping in and telling you to turn it down — or even off. Having a soundproofing consultant come in and evaluate your space for you is probably going to run a little high, compared to your allowance, but the good news is that you have many items lying around your house that would work quite well for a sound absorption check.
Choose several different materials, such as carpet, cardboard, plywood, foam, and bath towels, to test for sound absorption. Line your closet door with each material after you've placed a noise source inside and shut the door. To ensure uniformity, you probably want to have a prerecorded sound sample that you'll play for each soundproofing material. After you've lined the door, set the noise source to play, and then close the door. Record the noise you hear outside with an MP3 device.
After you've tested all of your materials, download each sound file to your media software. Then, read the results on the audio meters on your software package to find out which material absorbed the most sound — and kept it from coming out in the hall. You'll probably find that your more porous materials work more effectively than smooth ones; the sound just burrows its way into the holes. Smooth, hard surfaces can deflect noise away from the subject, instead of helping to build energy.
Sound and Balance: Testing the Inner Ear
If your balance is off, the culprit might be inside your ear. After all, the tiny mechanism that guides your hearing also can knock you off balance, if the liquid inside gets shaken up. Can sound waves themselves cause dizziness? This experiment will test it. You're going to observe the nystagmus — a twitching movement in your eye, from side to side, that happens while your body is trying to recover its equilibrium.
Do something that will make your test subjects dizzy. Whatever you do, it has to be the same for each participant. You could blindfold them and spin them around, or you could have them ride a merry-go-round, or twist them around in a swing, and let the swing turn back around to its normal position. All of those will work — just make sure you are consistent as far as method and period of time.
Right after you're done making your subject dizzy, play a sound. It could be a recording of the sea, the song "Time Warp" from The Rocky Horror Picture Show, a woman screaming, or water dripping. Record the amount of time it takes for the eyes to stop twitching. Then, put your subject back on the swing, or merry-go-round, and do it again — with a different sound. Repeat for three or four sounds each, for three or four different subjects.
Packaging Your Experiment
Even if you've put together a great experiment with sound results, you need to make sure that it looks professional if you're going to present it in a competition. Everyone's going to have a project board with three sides, but you want to make sure that your section titles are bold and all in the same font. A clean, clear font such as Arial or even Impact (if you're using MS Word) will work. Stencil and Engraver look impressive up close but will be difficult for judges to read, even from a short distance.
Put something out in the center as a visual display. Maybe a model ear, maybe a small radio, perhaps even a sound meter. This will give your experiment visual appeal.
Most importantly, though, present your results in a compelling fashion. Your graphs should be easy to read and in bold color. Even if there is detail to read on later pages, you want the judges to see something that they can understand, and realize the significance of, in the first few seconds. They have a lot of projects to evaluate, and you don't want yours brushed aside in the first look, just because of substandard presentation.
- PASCO: Noise Pollution
- Wheelan, Alexa J."Off Balance"
- Jacquelynne D. Vaughan's Sound Absorption Project