Look here
http://en.wikipedia.org/wiki/Microphone/
there is also information about, Electret condenser microphone, maybe you can combine them.
These values are very beautiful in German. http://de.wikipedia.org/wiki/Mikrofon.    http://de.wikipedia.org/wiki/Elektretmikrofon

A similar picture can be found at

http://commons.wikimedia.org/wiki/File:Mic-condenser.PNG