House of cards

Over at DIY Life and Boing Boing, they've been discussing a mysterious bike noisemaker spotted on the streets of Chicago. The device is apparently a battery-driven alternative to the old playing-cards-and clothes-pins-in-the-spokes trick. Small metal clips are attached to the spokes, and they pass by some sort of sensing device which is attached to a power supply and a speaker. The idea is intriguing, but the physics appear to be beyond the author...

Something electromagnetic is probably going on with this bike noisemaker. I'm not sure exactly what. I suspect that the things wired to the spokes are indeed magnets, and electromagnetic waves, sort of like radio static, are generated as they pass by the needle that's wired to the battery, then sent to the speaker and broadcast... but I don't know for sure. Any other ideas?

Eric Clapton, guitar and bike enthusiast, would surely jump in here and say that the mystery component at the heart of this invention is undoubtedly an electromagnetic pickup, of the kind you'd find on any dimestore electric guitar.

You might ask why or how this dingus is any improvement over the playing card approach. Well, that's a dangerous game, my friend. You're talking about extinguishing the human spirit that brought us the banana seat, the sissy bar, the ape hanger handlebar, and the folding bike -- great tonsils on the corpus bicicleta. (By the way, check out Turbospoke -- an all-analog spoke-card amplifier with a bitchin' "muffler"-- that's it in the picture up there. It's really more of an inflamed appendix than a tonsil.)