Microphone Not Working Macbook Air Yosemite

So I have Yosemite 10.10.4 and my microphone does not work in anything, under the system preferences the volume is set at max and the input source is correct.

The weird part is if I rub the computer with my finger nail the sound input meter goes up and down like its receiving sound.

I have tried doing a coreaudio, PRAM and SMC reset and no luck.