j-ivan -
There are a couple of things you can do.
1) The Touchscreens have buttons for volume control on the right side of the unit - turning the volume down might be a better option than muting it altogether.
2) Tap on the Settings App from the main screen, enter your passcode and select Touchscreen > Sound Configuration > Hometone Configuaration. From here you can change the sounds or select the silence option for each of the items in the list.
