I got my Macbook Pro 17inch (early 2011) back from Apple (they had to replace the logic board) 3 days ago, I had a terrible experience as the genious who gave me my solid state disk for safekeeping lost my disk's brackets thus I had to wait 2 more hours in the store until they find one from another machine, so they can put my SSD back. All these after 10 days of waiting for the repair. Today however I finally found time to use it and I noticed some weird sounds, like somehting is moving within the mac 1-2 times, even if I have no mechanical parts other than the fans, but my real issue at the moment is that my microphone is not working. I can see the mic in the System Info however and in Audio Midi Setup. In the Audio Midi Setup I see that the master chanel is turned off and I can't turn in on. Ch 1 and 2 are on full. I also noticed the first seconds after the comp. boots the blue bar goes to the middle in the System Preferences -> Sound -> Input. Any ideas what to do or try? I do not want to go back to the apple store as it is more than 50 minutes away from here and I need my laptop as a computer science student, so RMA it is out of the question until my exams are done. Everything else is working perfectly, in fact better than before (temps and noise level of fans).