The Mute button on the toolbar () turns off sound for all Ascendis Caller ID actions.  Actions that play a sound or speak will do nothing when this is checked.  This applies to use of the 'Test Action' command as well as when Ascendis Caller ID is processing calls.  This has the same effect as disabling sound in the Options window.

When muted, the button on the toolbar changes to .  Click it to re-enable sounds.