when you unmute the mic, anything said into the mic will come out the speakers. When you place a mic too close to the speakers it is outputting to, you get feedback. Adjusting the volumes "may" have fixed the issue, but really, (if the mic was built in) sony placed the mic too close to the speakers... also taking the 20 db boost off of the mic may have fixed the problem as well. I'm a fan of Toshiba laptops these days, they seem to work excellent...except all the pre-loaded software crap they have.