I got the new iMac G5, but unlike the old G4 iMac that has the microphone on the front panel, the new iMac's is located right next to the fan. This causes a " hissing " sound when I audio chat using iChat. I want to use an external mic, any recommondations?? I have a couple if those clip-on mics, that you use at meetings and conferences but they didn't work?? how come??