Creating an electromagnet and sound wave learning environment
I’ve been meaning for a while to write more about one of my recent projects, Catch the Wave!. Originally it was made for last year’s Oregon Science Festival and since I’m exhibiting again at the festival this year (this weekend, in fact!) I thought now was as good a time as any.
What is it?
Catch the Wave! is a public science education project, with the side goal of bettering my own ability to make a museum-caliber interactive experience.
The project is a series of four small, colorful, table-top wooden cabinets with physical controls and screens, each of which explores a concept related to electromagnets and sound waves and how they are used for audio recording and playback.
Catch the Wave! has been a personal challenge and a labor of love. Aside from the building of it, I’ve staffed several full days’ worth of events at multiple locations in order to benefit the community at large in an educational way.
Why?
The main prompt for this project was an opportunity to submit a proposal for my local science museum’s inaugural STEM event — the Oregon Science Festival.
Beyond the initial event, I’ve been wanting to work on something for the public that is more portable than, say, an eight-foot xylophone, more directly learning-oriented, and something in line with my continued interest in synthesized audio and waveforms.
The four stations
The exhibit is meant to be approached in order, each station building upon previous stations’ concepts.
Station 1: What is an electromagnet?
What is an electromagnet? Turns out, if you wrap some lightly-insulated wire around a metal core and then run electrical current through it, you create a magnet. Turn the current on, it’s a magnet. Turn it off, it’s just a coil of wire. You can directly experience the connection between electrical current and magnetism.
Participants can push a button to run current through a professionally-wound electromagnet and get paper clips to stick when it’s on. Jaws typically drop when this is demonstrated and it’s begging for hands-on fun as people attempt to see how many they can get to stick.
Station 2: Changing magnetic polarity
If you run current through the coil in one direction, the magnet’s polarity is aligned a certain way (you can read more about the right-hand rule). If you reverse the current, you reverse this alignment. So the second station is a larger version of the first station’s electromagnet hooked up to a two-way toggle switch. Suspended above the electromagnet is a permanent, regular magnet on a swing which can be attracted and repelled as the magnetic forces change. So now you can see how electrical current and physical motion are related! Folks seem to also have a lot of fun with this one as they attempt to get the swing to move the most distance or to see how fast they can switch the current’s direction.
Station 3: Fast changes make sound
Imagine if you could flip that switch, as well as the magnetic polarity, hundreds or even thousands of times per second. Or imagine it more like a slider, controlling how much current flows in a direction. A computer or a synthesizer is able to do this electronically. If you then have a thin membrane like paper or plastic that can be moved by this physical interaction between the permanent magnet and the electromagnet, the vibrations of the membrane vibrate the air around it. If your ear is close enough, and the number of vibrations is in a certain range, the vibrating air also vibrates your eardrum and you can hear a sound! This is what we call the frequency of a sound.
The station lets you play with a knob to adjust the frequency in the audible range, as well as the waveform.
You can think of the waveform as the pattern of movement of the membrane. Quickly switching between fully one direction and fully the other is a square wave. Switching more slowly in one direction, but quickly in the other could be described as a sawtooth wave, rising before sharply dropping.
These waveforms sound different to our ear. And you can even feel the sound by touching the center of the speaker at the lower frequencies, much like how you can feel a subwoofer’s sound. This is because the membrane vibrations are moving the tissue in your body as well as the air around you.
Even at its most basic level, people have fun with this station since it makes noise and has very hands-on controls.
Station 4: Complex waves
The last station lets you record your own voice into a microphone, then play it back, optionally with effects applied like pitch shifting, reversing, and echoing. The same electromagnetic principles are at work in this system, but here you can just focus on the fun of sound.
The everyday sounds around us like speech, music, or nature rarely sound just like synthesized sound coming from a computer. This is because they are formed of many overlapping and interacting waves to add richness to the patterns. Using electromagnets, we can record the electrical signals made by sound and then computers can alter these signals before playing them back.
People love hearing their own voice in “chipmunk style” or a lot higher or lower frequency than their normal speech. It’s a very concrete way to see how these concepts apply to everyday life and to practical effects.
Reactions to the project
I’ve gotten a lot of feedback from kids and adults alike about how much they like the progression of concepts in the project. People range from having no idea about how any of this worked to being involved directly with some of the concepts — musicians, equipment builders, teachers, and others — but still taking something away from the stations’ hands-on nature. It’s been very gratifying for me to give something to people in this way.
Future installments
In future posts, I’d like to talk about some of the build details as well as some of the educational considerations and takeaways that went into and resulted from this project.
- Chromebooks are amazingly hackable!
- They don’t have to even look like Chromebooks!
- Table saws are wonderful tools for repetitive work!
- Sanding, priming, painting, and clearcoating is a laborious process!
- Some kids have never seen an audio speaker!
- Kids can have fun with tech that isn’t a touchscreen!
And speaking of kids and having fun, I knew this already in the abstract, but kids can always educate you very directly when it comes to user interfaces and the gulf between their intended and real-world uses. I feel like as with many projects, I’ve learned a lot myself even with this project that was intended as a teaching experience.
As with all of my projects, please get in touch if you’d like to talk about Catch the Wave! or get more info.