heterodyne: To combine by intermodulation (two alternating signals, esp radio signals) to produce two signals having frequencies corresponding to the sum and the difference of the original frequencies

I wanted a way to visualize beating sound patterns
circular one footer bride
Circular “one footed bride” adapted from Harry Partch’s book “Genesis of a Music”

Humans perceive consonant (harmonious) and dissonant (clashing) sounds from the relation of frequency ratios:
2/1 (220/110), 3/2 (220/146.66, 4/3 (220/165), 5/4 (220/176), and 8/5 (220/137/5). On the Heterodynr, the frequencies of two tones are mapped to the position of each arm.

Starting at the 12 o’clock position, the frequency will be the note A (220 hz). As the arm lowers to the 6 o’clock position, the note will also be A, but one octave lower (110 hz). By moving the arms in different positions, one can see and hear ratios of frequencies. The heterodyning beating effect should become more apparent when the arms are very close to each other.

You will also notice the color of lights changing because each arm is mapped to the color spectrum, with C being red at the bottom of the rainbow, continuing up, and eventually repeating.


Tech notes:

  • Each arm contains a particle photon connected to an accelerometer which is constantly sending its Z axis using multicast OSC (Open Sound Control) messages
  • A node.js server converts the OSC messages to the correct frequency and also calculates the correct RGB value for each arm light color which are then re-broadcast as new OSC messages
  • A python script listens for the light OSC messages which in turn controls a lightify gateway
  • To be able to power the particle photons I need to embedded a wire through the base and send power through bearing gears. I designed a special 3D printed hub to use the steel mount post as the common ground and routed the positive 5v through a custom isolated bearing mount.


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