If your microphone is too close to your speakers you may encounter feedback.
Some configurations offer a headphones jack.
Plug headphones into the headphone jack or the sound output jack if you do not have a headphones jack. In either case this should disable the sound output through your connected speakers. This utility has not been tested by us therefore use of this utility is at your own risk. Apple does claim that users have reported this utility works reliably. A download link for this utility is provided in the Apple technote dicussed below.