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By humming, singing, or talking into the Vocal Visualizer, you’ll be able to see sound as vibration (or pressure waves) and experience Lissajous patterns and resonant vibration modes.
Make the vibration chamber:
Make the frame:
Make your final assembly:
Important safety note: Never point a laser into anyone's eyes, including your own!
While your device is on a table, carefully aim the laser beam at the mirror on the membrane. You may need to adjust either the laser pointer or the vibration chamber to get it just right. Use the T-joint to tilt the laser pointer up or down. You might also need to rotate the vibration chamber to line up the laser and the mirror perfectly.
Once the laser is hitting the center of the plastic mirror, check to make sure that a crisply reflected laser spot is visible.
Aim your Vocal Visualizer at a wall, screen, floor, or other flat reflective surface. Again, never aim the laser pointer or the reflected beam directly at your own or anyone else’s face or eyes.
Hold the Vocal Visualizer’s vibration chamber close to your mouth. Hum, sing, speak, or make weird noises into it. As you vocalize, try changing your pitch (frequency) and your volume (amplitude) and take note of the different results.
When you vocalize, you cause air molecules to vibrate. These vibrating molecules strike the rubber balloon membrane. The membrane vibrates, causing the mirror to wiggle in turn. The laser light bounces off this wiggling mirror, tracing out various shapes and patterns that you can see. (That’s why we call this the Vocal Visualizer!) The different amplitudes and frequencies of the sounds emanating from your mouth cause different shapes and patterns.
The harmonic motions traced out by the moving laser beam are called Lissajous patterns. The combination of the mirror moving in an up-and-down direction (along the y-axis) and the side-to-side direction (along the x-axis) create the patterns you see on the screen.
Some shapes will look chaotic while others will be more regular and repeating—circles, ovals, figure eights. Various frequencies will cause the rubber membrane to dance around in resonant vibration modes—standing waves of fluctuating hills and valleys on the membrane’s surface.
Your mirror and laser also act as an optical lever. If you change the distance from which you broadcast the laser’s reflection, you’ll also change the size of the image that’s projected. Stand closer to your flat surface and the reflected image will be smaller; stand back and the reflected image will be larger. You can achieve a similar effect by experimenting with the volume of your voice—speak or sing loudly into the device and your patterns will be large; speak or sing softly and your pattern will be smaller.
What kinds of patterns can you create with your voice and the laser? Which sounds make which patterns? What makes your pattern bigger or smaller? Experiment to see what you can do.
Try swinging your Visual Vocalizer quickly back and forth while you sing or hum and see if you can make a wave pattern.
Hold your Vocal Visualizer up to a stereo speaker and play your favorite song. What kinds of patterns and rhythms does it make on your wall?
Invite a friend who also has a Vocal Visualizer over and make a laser light show together.
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Attribution: Exploratorium Teacher Institute