Swedish artist Max Björverud turned the ordinary toilet paper roller into a sophisticated instrument at an installation at the SNASK creative agency in Stockholm. Hack A Day explains how it works:
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Inspired by the way bicycle computers determine your speed, [Max] took a set of toilet paper holders, extended each roll holding part with a 3D-printed attachment housing a magnet, and installed a Hall-effect sensor to determine the rolling activity. The rolls’ sensor data is then collected with an Arduino Mega and passed on to a Raspberry Pi Zero running Pure Data, creating the actual sounds. The sensor setup is briefly shown in another video.
Source: neatorama