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Course: Exploratorium > Unit 1

Lesson 2: Vocal Visualizer
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Exploratorium
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Vocal Visualizer
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Vocal Visualizer: Complete activity guide

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Croon a tune, croak like a frog, hum, hoot, or holler—you don’t need to be Pavarotti to transform laser light into dazzling shapes and patterns with the power of your voice.

By humming, singing, or talking into the Vocal Visualizer—a simple sound oscilloscope—you’ll be able to see sound as vibration (or pressure waves) and create a variety of cool laser-light patterns that are reflected on a wall or any other flat surface. It’s a fun and slightly psychedelic introduction to concepts such as Lissajous patterns and resonant vibration modes. A Pink Floyd soundtrack is entirely optional.

Tools & materials

  • A laser pen/pointer with low power output. Try to find the common variety of laser pointers that are about the diameter of your pinky finger (approximately 1.4 cm or 9/16 inch diameter).
  • Rubber bands
  • One 11 inch diameter balloon
  • Double-sided tape
  • Small plastic mirror
  • Various lengths of PVC pipe: one 6 foot (approximately 2 meter) length of half-inch diameter pipe; two half-inch diameter “elbows”; three half-inch diameter T-joints; and 10 cm length of 3 inch diameter solid, smooth-walled drainpipe
  • Safety goggles
  • Measuring tape with both English and metric units
  • Permanent marker
  • Scissors
  • Pliers
  • Hacksaw
  • PVC cutter (optional)

Assembly

Vibration Chamber Assembly:
  • If your 3 inch diameter, smooth-walled drainpipe is longer than 10 cm, use the hacksaw or PVC cutter to cut it down to 10 cm.
  • Use the scissors to snip off the neck of the balloon, cutting about halfway between the opening and the widest part of the balloon.
  • Stretch the balloon over one of the open ends of the 10 cm-long segment of drainpipe from step 1. This is your balloon membrane.
  • Don your safety goggles. Wrap a corner of the plastic mirror in a piece of folded paper and grip the corner with the pliers; use the pliers to break off an approximately 1 cm2 piece of mirror (it’s okay if the piece is irregularly shaped). If the mirror has a protective film on it, peel it off.
  • Place a small piece of double-sided tape on the balloon membrane somewhere between the membrane’s center and its outer edge.
  • Affix the piece of mirror—shiny side up—to the membrane by sticking it onto the exposed side of the double-sided tape.
Well done! You just made your vibration chamber.
Frame Assembly:
  • Using a hacksaw or PVC cutter, cut the half-inch diameter pipe into the following lengths: two pieces, each 3 cm long; one piece, 5cm long; three pieces, each 12 cm long; and two pieces, each 50 cm long.
  • Arrange your half-inch pipe, elbows, and T-joints as laid out in the image below (or watch the "Build Your Own Vocal Visualizer" video):
Vocal visualizer PVC pipes
  • Insert the pieces together, making sure your connections are snug. The frame will form a trapezoid. The narrowing of the pipes helps to better support the vibration chamber.
Final Assembly:
  • Place the vibration chamber atop the two 12 cm-long pieces of PVC pipe with the membrane and mirror facing towards the trapezoid. The membrane can touch the T-joints but shouldn’t sit on top of them. The open end of the vibration chamber should extend a little beyond the ends of the pipes.
  • Secure the vibration chamber to the frame by looping two rubber bands around both the two 12 cm-long pipes and the chamber (see image below). ​
Vocal visualizer vibration chamber
  • Insert the laser pointer into the 12 cm length of half-inch pipe located inside of the trapezoidal area. If the diameter of the laser pointer and the pipe match up, inserting the laser into the tube fully will turn it on. If the pocket clip gets in the way, remove the clip with pliers. If the pipe’s diameter is larger than the laser pointer, bulk up the diameter of the laser by wrapping some masking tape around it until you get a good fit.
Vocal visualizer completed build

Things to do and notice

Safety note: Never point a laser into your or someone's eyes.
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 rotate laser pointer in the pipe 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: be sure to never aim the laser pointer or the reflected beam directly at your 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.

What’s going on?

When you vocalize sounds, you cause air molecules to vibrate. These vibrating molecules hit 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.

Going further

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 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!

Resources

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