If your presentation includes computer audio, make sure the volume control on your computer is not turned all the way down or muted. In Windows, you may be able to check this by clicking the volume control in your Windows system tray (lower right corner of the screen). On a Mac, you may be able to adjust the volume from your menu bar (top right corner of the screen) or via the volume control function keys.
If you’re using a computer audio cable, make sure it is connected to your computer’s headphone jack or audio out jack. Connect the other end to the projector’s Audio port (beneath the Computer2 port) when the computer’s video cable is connected to the Computer1, Computer2, or BNC ports.