Hello there! Sounds like the mic is not being detected please follow the steps below to reset the sound system that should bring mic back.
1. Shut down the computer.2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.3. On the keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.4. Release all the keys and the power button at the same time.5. Press the power button to turn on the computer.6. Press and hold the Command-Option-P-R keys before the gray screen appears.7. Hold the keys down until the computer restarts 3 times ( you will hear the chime 3 times).8. Release the keys.
Hello again. I am posting back because i have not heard from you hopefully this a good thing as your problem is possibly fixed. Please either post back if your still having problems or just rate this reply