PCmount condensor microphone
Audio is a somewhat difficult input to use unless you have an amplifier to make your values usable. The “Super Snooper Big Ear Audio Amplifier Kit" from Jameco ($10.95) proved to do the trick for me. It was able to give me a basic reading which I was able to decipher. In my case, the original microphone was lost and I had to replace it with a "PC-Mount condenser Microphone Element"
Model: 270-090 | Catalog #: 270-090 " from RadioShack, ($2.59)
This worked pretty well, except that the read-outs on the serial com were in a different range. All this did was caused me to alter the values in my Arduino code.
*Attached is the data sheet for the kit
super snooper