Tasked with capturing an autonomic response, my immediate thoughts went to Marco Donnarumma (Marco’s site ), whose work is in making expressive music using the electrical noise emitted from his muscles. This electrical sound is called MMG (or Mechanomyogram). I took a workshop with him in May of 2012 at Harvestworks. The genius of his sensor-performance lay in the software platform he developed in Pure Data. The sensor itself is a medical grade electret microphone and a simple “amp” of sorts. In an interview in “Create Digital Music” article he states that “I do hope to see the system hacked and extended…” and taught the workshop to share the platform.
I have one of these devices, soldered together from that workshop, and my mind, during the lecture in class, went to trying to hear my muscles twitch.
I had to figure a way to make the sensor useful to Arduino and not the Pure Data platform it is intended for. I had to create an amp that the Arduino could read through Analog In. So I looked at Op Amps and breadboarded one. I used the LM358 Amp (found in the shop) and wired the breadboard for this circuit schematic:
The above is an image of the Op-Amp I made.
The above is my attempt to understand the oscilloscope and use it to better understand my circuit.
I had help, but I believe the resistors the schematic called for to be too large to give the mic the sensitivity I need.
Despite this, I tested the mic on parts of my body. The set-up I have now is would not work on the areas of the arm that had previously registered sounds through the PD environment. I tested several other places, but the one place I feel that I might be successful is in my hand. It was evident -on the oscilliscope- when the readings registered a vibration from a jostle, as they spiked in appropriate ways. However, I had my fist clenched around the mic. The waves of the oscilliscope moved like a calm lake.
I plan on adjusting or remaking the op-amp I breadboarded to give me the sensitivity I need to sense MMGs.
I borrowed a breakout Op-Amp and tried it with the Mic from the X Sense.
I hooked that up to the oscilloscope (and got a lesson from Surya).
It did not work.
I hooked the wires up in a variety of ways, and banged my head against the wall for a while.
So I said enough and ordered myself a new op-amp and several mics.
I got the Breakout board (a preassembled Op-amp and mic). Soldered it up, plugged it in and found that I have no sounds in my arm. Nothing that differentiates it apart from noise.
I did plug in a mic to ableton live and shove it against my skin in various places. The only viable sounds were in my guts.
Even those were not that useable.
So I attached it to my bicep….
I graphed this data while working in the shop.
It looked like this:
525,,525, 528,527,527, 527, 527, 525,528,527,525,526,526,525,525,526,525,
I plan on getting the MMGs later on this week. In conjunction with those readings, I will get data from my google calendar and compare my activities with the flexing of my arms.