So the other day I booted up into OS X and was going to make a short video in Photo Booth with my friend. I recorded a video, but when I tried to play it back there was no sound. I tried recording another video, this time yelling at the top of my lungs. This time when I played it back, I could hear my yelling very faintly. I decided to open up the System Preferences to see if the microphone was picking up any sound. The input level showed that there was a little bit of static, but the bar barely moved when I yelled. Here's where it gets weird. I opened up Skype and called "echo123" to see if Skype was picking up and sound. After the call recorded my sound, it played it back and to my surprise it sounded perfect. It was like my microphone didn't have a single problem. I then opened up Photo Booth again and the System Preferences to see if it would pick up and sound from my microphone. And once again it would only barely pick up sound when I was yelling. After a few minutes, I finally decided I'd take my MacBook to the Apple Store. But before that, I decided I'd just try a little trick that worked on my iPod earbuds when one of them wasn't working correctly. I flicked my finger against the plastic right next to where the microphone is above the screen. I opened up System Preferences and to my amazement my microphone was now working perfectly! This is definitely one of the weirdest problems and actually the only problem I've had with my MacBook so far. I just thought I'd share this experience for any other people who might be having problems with their internal microphone.