Post originale di: Chris Green ,
I've read a few comments on different forums, such as [https://discussions.apple.com/thread/2373443?tstart=0|this one], about the microphones in these computers, and I wouldn't be so sure that the issues are your fault. Microphone problems seem to be pretty common on these machines. Some can be solved by a reboot, PRAM reset, or even unplugging and reconnecting external speakers or other peripherals. Try the PRAM reset on the next one that you fix and see if that fixes it. You should be able to easily test the microphone in the audio settings menu.