Month: April 2019

Microphone Polar Plots

For a while, I’ve been thinking about noise cancelling microphones. I realized the other day that in order to ever hope to build one, I needed to model it first. What I ended up doing was building a model in matlab (of course), which includes the following simple classes:

  1. A waveform class to allow for quick generation of sine waves.
  2. A wavesource class to allow positioning of those waveforms in space.
  3. A microphone class to generate wave recievers positioned in space, which computes the distance between itself and the source in order to phase shift the incoming wave.

Then, to get waveforms, you can take the output audio from multiple microphones (which is effectively time aligned) and do math with it.

Then, by sweeping the wave sources through space, we can plot the pickup patterns of different wave forms.

By sweeping the frequency of the waveform over successive sweeps, we can see that impact as well.

Fun. More to come?

Get the code here: https://github.com/wespo/DirectionalMicrophone

The Roboticist’s Garden

Just a quick one — I haven’t posted here in forever, and I have lots of things which I really should document. This is one that I finished a few weeks ago but was super quick. Basically, it’s just an artsy-fartsy lamp. I built it using this light bulb, from Amazon, some styrofoam to create the mid-lamp platform. Fake grass from Michael’s Crafts for the grass.

The original bulb for the bottom that inspired the design was a 25W incandescent ‘stained glass‘ bulb, but the heat from that bulb trapped inside the glass cloche would quickly begin to bake the oils out of the fake grass. This was a pretty severe fire hazard, so I took an LED bulb and hand painted it using sharpie paint pens. A little gauche, but it adds a certain wabi-sabi value to the art that matches the hand crumpled copper tape which rings the ‘grass’ platform. All in all, I’m pretty pleased with how it came out.