Sounds Mirrors & Lasers

Have you ever wondered what shapes sounds can make? After a night of research, I decided to experiment using a roll of tape, a small mirror, a balloon, a laser pointer, and a Python program I had coded and modified from a YouTube video. I put the balloon over the tape roll like a drum head and put the mirror in the middle of the balloon head. I pointed the laser to reflect off the mirror, and I put a speaker under the balloon head, and I played tones through the speaker. Much to my disappointment, the shapes projected by the laser were small and had almost no shape. After time had passed and the balloon stretched out and became looser, I tried again and was able to replicate the shapes I had seen during my research. With this experiment, I began to wonder about how I will be able to conduct research using this apparatus.

My questions were, how do sounds affect the shapes that are created using this experiment? Do higher notes make faster-moving shapes, or vice versa, to lower notes making slow-moving shapes? Do harmonious chords that sound good have better shapes than dissonant chords that sound bad?

I hypothesized that chords with less dissonance reflect a more uniform and symmetric pattern, while Chords with more dissonance reflect a more bizarre and unsymmetric shape.

In the first few experiments, I had trouble with the tension of the balloon, which continued to be an issue throughout the tests. Only when I let the balloon loose tension and re-tried the test, did I realize that it needed to be loose, but if it was too loose, it wouldn’t vibrate at all.

To create the best results I could get, I designed three drums (see 1A), 2in high, and 2-4in wide, for different tests, so I could find the best to use.

Using my 3D printer, I printed the 3 drums and attempted to stretch balloons over the rims of the drums. I quickly ran into a problem with the tension of the heads. After trying different kinds of materials like latex gloves, I decided that balloons are the best kind because they vibrate evenly and absorb the most sound. I got the 2in and 3in drums to work, but the 4in was too tight because the balloons were not big enough (see 3A). However, the only difference between the 2in and the 3in was the size of the shape, but the original 3in drum broke (see 2A), and the tension was too high on the other 3in drum, so I went with the 2in drum because it gave the same results and was more manageable.

once I had an operational drum, I switched my computer to an electric piano. Using a specific setting on the piano to produce pure tones, I hooked it up to a speaker and started making observations. I even tried hooking it to my guitar, which worked, but to keep things simple, I kept it on the piano.

However, I still had a problem. I wanted to be able to show the electrical wave that the speaker was getting, and I wanted to show the shape that it was producing at the same time. To do this, I first took apart the speaker to attach my 20$ amazon oscilloscope to the positive and negative ends of the speaker (see 4A).

Once that was working, I needed to redirect the laser projection that it made. To do this i redirected it with large mirrors I was able to find around the house. What this did was amplify the size of the projection and have it appear behind the oscilloscope. The oscilloscope was especially useful because I was able to visualize the waves, so I could see the wave variable in case the projection started changing unpredictably. With this setup (see 5-5.2A), I was able to record my experiments.

I have maybe spent 6 hour or more hours playing music into this thing! its really fun and cool to see the shapes that chords and sounds make!

I found out that two of any note played together, no matter the dissonance, always look like the two single tones added together. Which shows that playing two tones simultaneously adds them together.

I also hooked it up to my guitar and was able to have fun playing my favorite songs and see how it looked in the oscilloscope and the laser projection.

With this apparatus I was able to prove that the shapes produces by thing rely on the harmony of the notes played creating more bizarre or clean shape depending on its dissonance.

an Example is I played a G with every note up till the next G and I saw that the cleanest shapes were produced by C and D and looking at the harmonic series C and D are the perfect 4th and 5th of G