Instructions
Turn on your Xbox 360.
Press the "Guide" button--the large button in the center of the controller--to bring up the guide menu.
Select "Preferences" from the menu, then select "Voice."
Highlight the "Mute" option and press the "A" button on the controller. Highlight the "Volume" slider bar and slide it all the way to the left. This will mute all the headset functions.
Insert your Xbox 360 game disk into the disk tray, then start the game as normal. From there, select the "multiplayer" option, followed by the "Online" or "Xbox Live" option. You will now be able to play the game without any noise or interference from another person's headset.