Kenna's (and my) Science Fair Project

Yesterday was the Science Fair for Kenna's school. For a couple of reasons, I had high hopes that her project would do well. The first reason was that Todd did very well when he was that age, going on to win first place at the district fair. The second reason was that I was the one that thought of her experiment and am very proud of myself for thinking of it...probably a bit too proud.

As you know, I have a degree in Physics. It's something that I enjoy, but it won't surprise you to learn that I don't get to use it much. On the rare occasion I get to apply my skills, I really get into it. So when I first learned about the science fair, I started thinking pretty hard of the perfect experiment.

Originally, I had wanted to measure the speed of light. I thought that would be about the coolest experiment that I could pull off. I even thought of a way to measure it using a laser pointer, a mirror, and a spinning bicycle tire. But after a few calculations, I realized that either the mirror would have to be a couple of miles away from the laser pointer or else the bicycle tire would have to be spinning a few hundred miles per hour. I decided to settle on something a bit less ambitious: measuring the speed of sound.

Before formally proposing to Kenna that she use my idea for her project, I decided to do a proof-of-concept experiment to make sure it was even possible to measure the speed of sound using household items. So one night after the kids went to bed, I got my Physics on.

My initial tests went very well. I won't bore you with the details, but I was able to measure the speed of sound using only my laptop computer. Okay, it was so cool that I have to bore you with the details. First I installed a free software application called Audacity that allows recording and editing audio. Then I created a sound file that would play a loud click on just the right audio channel. My laptop has stereo speakers and also stereo microphones. These features allowed me to start recording, play the audio file out of just one speaker, then visually examine the recordings of both the left and right audio channels. Because the microphones are about two inches apart, the right microphone picks up the sound slightly before the left microphone. The time difference is only 1/6700 of a second, but the standard recording takes a sample every 1/44100 of a second. So, the difference is about six or seven samples in length. Using a bit of algebra and arithmetic I was able to measure a speed of about 700mph, which is within 7% of the expected value. Not too shabby.

Measuring the speed of sound using Audacity

The next day I excitedly proposed to Kenna that she use my idea for her project. She certainly didn't get as excited as I was, but she did agree. We knew the final experiment would need to be more scientific that just a single measurement of the speed of sound. After some thought, we came up with the idea to measure the speed through different materials.

Kenna got the idea approved by her teacher and then started doing all the necessary research. You already know that Kenna is great at doing any kind of project. The science fair project was right up her alley. She was in charge of creating the report and the display board. She also came up with a list of materials she wanted to measure the speed of sound through. I was in charge of performing the actual experiment.

My initial measurement had gone so well that I assumed other measurements would be simple. Boy, was I wrong. I was ultimately able to devise a simple way to measure sound through other materials, but it sure took me a lot of time to get there. I spent hours and hours over the Christmas break trying to measure the speed of sound through water. I tried what felt like a million different methods, but finally had to scrap that idea. My final solution required two microphones that I bought for $5 each at Walmart. I connected them with a y-adapter and plugged them into the microphone jack of my computer. I then placed them both on the floor and hit the floor with a hammer. The microphones picked up the sound as it traveled through the flooring. We repeated the experiment for wood, tile, and cement flooring.

I learned from Todd's science fair successes that the key to doing well is the ability to clearly explain the scientific concepts involved. So I made sure Kenna understood the nature of sound waves and why they travel at different speeds through different materials. Of course, my efforts were unnecessary because she did such a good job with her research. She also made a great looking display. I went to the awards night fully expecting her to be a winner.

There were about 80 entries in the school fair. They chose 25 First Place winners and then they narrowed it down to seven Best in Show projects that would go on to the district fair. When they announced the First Place winners, they had them all come up on stage. We were not surprised at all when Kenna was selected. Then they started announcing the Best in Show winners. There was excitement and anticipation, but not any suspense as they announced the winners. They made it to the last two names and I still had full confidence the entire time.They finally announced her name second-to-last. She had a big smile on her face when they gave her her ribbon.

The district fair is February 22. I'm sure she'll do very well.