I have tried using the built in mic as well as my gaming headset, and neither are picking up any sound. Both worked 2 days ago, nothing changed that I am aware of, and I'm certain the headset works (it works on another computer). Anyone able to help?
Double check the setting for Input volume. System Preferences > Sound > Input tab > highlight Internal Microphone. Normal setting is about halfway on the slider. You can snap your fingers or cause other noise and see the reading on the meter.