I am really confused at this moment. I have the following microphone: http://www.farnell.com/datasheets/1660938.pdf

What I want to do is make a actual dB meter with this sensor. So I would net to know how much the voltage changes for example when the sound changes with one 1dB? How do I calculate that with the above datasheet? It has something to do with the sensitivity but what and how?