Mute or change the volume for FaceTime calls on Mac
There are several ways to control the volume of calls in FaceTime on your Mac.
On your Mac, do any of the following:
Mute yourself: In the FaceTime app
, move the pointer over the call window, then click the Mute button 
(or use the Touch Bar). You can still hear the other person on the call, but they won’t be able to hear you.To unmute yourself, click the Mute button again.
Change the volume of your microphone: Choose Apple menu
> System Preferences, click Sound, click Input, then drag the “Input volume” slider.Change the volume you hear: Change your computer’s volume. See Turn your Mac volume up or down.