Microphone wired up to graph changes in skin surface potential as changes in muscle contraction. Using Audacity(an audio editor that I use for all of my "sick dubstep beats") one can use the amplifier at about X57dB and then use the noise removal tool. Be sure to take a sample of empty electrodes or in other words, electrodes not in contact with a contracting muscle. This will give plenty of noise sampling space for algorithm. The longer incipit section the better.
One can also take an EKG, now remember that you should place the electrodes on the opposite side of the body for each pair, so across whichever line of symmetry, so:
should be wired in the following pattern(same colors means each is an element of the same pair of electrodes):
There are multiples for the black set which is symmetric across the transverse, but that is okay, the resistance of one side should be equal to the other if the path is the same(one cannot use displacement obviously).
Now for the actual measurement system:
The microphone is used only because it has an op amp and USB converter built directly in, which is quite useful, because the data can be easily stored and manipulated. Now I recommend using well insulated cables for the electrodes, perhaps even negative feedback(to a control sample ground) however this is unnecessary if one uses the standard av cables which were all the rage in the 1990's. I then coated the majority of the head in wax leaving only a small point exposed. I recommend keeping the wax at the melting threshold, that way it quickly solidifies on contact with the electrode and then we can build up multiple layers.
Now if you already looked at the eeg project, you could use those wet electrodes, made with a sponge,solution(salt),and wires. For a gel, you could use something with a glycerol like viscosity possibly mixed with an ionic or make conductivity an innate property of the substance a thick polar substance like the mucilage of plants, but very conductive. Any who, this gel issue can be avoided by using these dry electrodes.
One could also modify the electrodes but be careful because the more surface area exposed the more noise. However these electrodes easily mount to the wrists and arm for measuring contractions of the forearm muscle region.
