Check the volume on the control module. There are two volume controls. One for the game, the other for the chat. Check to make both are turned up. If that fails, there may be something wrong with the control module. Refer to the repair guides and troubleshooting page for this device for more information.

Your right speaker is probably blown. Please refer to the repair guides for this device for information on how to repair it. Following them step by step will make for an easy repair.