Music for Oscilloscopes

First, a story:

Many moons ago, before laser pointers were things you could get at your local convenience store for the cost of a few packs of gum, back when lasers were expensive and cool, my friend got a laser. I’m pretty sure it was discarded by some lab. It was a tube about 5 cm in diameter and about 30 cm long and had a large brick-sized power supply. It was fun to play with, but ultimately it’s just a laser making a red dot on the wall. So Phil, for that was my friend’s name, took a speaker from his stereo, and taped a small mirror to the cone. Then, with the lights out, aimed the laser at the mirror and played music. Suddenly, the music came alive on the ceiling where the laser was being reflected. We called it Philsarium, after Laserium, which had been shown in the 1970s at planetariums.

That’s it for the story. Not much of a moral, I admit, but it was more of a trip down memory-lane. Anyway, the reason I bring it up is this week I saw a certain Smarter Every Day video. This video immediately brought that experience back to mind, except this time the laser is replaced by an oscilloscope. Oh, and instead of using regular music, awesome people in Austria craft music specifically to show different things on the oscilloscope. What normally shows sine waves or square waves (or RS-232 signals that Phil and I had to reverse engineer at one point) now shows everything from Tetris blocks to Tyrannosaurus Rexes.

Like Phil’s laser, the oscilloscope also shows a dot. Normally it shows various waveforms for analysis, but really it just shows voltage visually. By splitting the music’s stereo signal into 2 lines (one for the left speaker, the other for the right) and connecting these 2 voltages to the oscilloscope’s two inputs, the oscilloscope’s dot can be moved around the screen based on what the music does. One input (say the left audio channel) controls the horizontal, and the other input controls the vertical, moving the dot around the screen. By adjusting the voltage for the two channels carefully, you can turn the oscilloscope into an Etch-a-Sketch. And by having the sound change the drawing changes, and you can move and change the image. OK, it may be a long way to go for what is today considered mere music visualization, but doing it on a ‘scope is brilliant.

Those wacky Austrians have made albums of music based on this. The music is constrained by it’s primary audience, the oscilloscope, so it sounds somewhat like raw old school synthesizer music.

There’s a lot of trigonometry involved in this, so the next time a student asks a math teacher “when will we use this”, the answer may be “when you form a band.”

Bulletin boards to Whiteboards

My new classroom has one good-sized whiteboard flanked by 2 bulletin boards. The previous teacher used the ends of the whiteboard to write down Objectives, Homework, etc. This took up a lot of the usable space, and I want to be able to use the whole whiteboard during lessons. So I have a plan to turn them into whiteboards. Then I can use one for the 6th grade, and the other for the 7th.

I bought plexiglass and cut it into appropriate sizes. This didn’t work as well as I had hoped, and there are some chips gone from when I was breaking off the extra. *sigh* Then I spray painted them white and mounted them to the existing bulletin board with the white side in, and the smooth side out. I should be able to use them just fine.

Should. You know how that works. It looks like colored dry erase markers erase just fine. But black doesn’t want to erase. Water didn’t work. Isopropyl alcohol didn’t work. Fortunately Acetone did.

So I’ve ordered some white dry erase contact paper from Amazon. It’ll arrive after classes start, but that’s OK. We’ll just have to see how it goes.


[[update 9/24/2013]]

The contact paper arrived and has been working pretty well. It was tricky to install, and there are wrinkles where I didn’t manage to get it just right. There is a bit that doesn’t want to stick on and starts peeling up, but overall it’s holding well. Oh, and all the dry erase colors erase just fine.