OSX 10.6.8 internal mic does not register voice in PhotoBooth but registers in system preferences I am having issues where so far PhotoBooth video recordings and flash based web applications do not register my voice using the internal mic.

I have also tried with and without plugging in headphones (no mic on head phones).

System Preferences -> Sound -> Input however does register my voice as well as System Preferences -> Speech -> Speech Recognition -> Calibrate
I know this is a stupid question but it just caught me when I was looking into your problem. Are you sure you have output set to Internal Speakers not something else like an Airplay device?

When you set the "Sound Effect" do you get noise out of the speakers