how to mute FaceTime ringer

Hi all,

After installing Yosemite and playing around with it a bit one question remains.. is there anyway to mute the ringer from FaceTime ?

Receiving the iphone's calls directly on the mac is pretty awesome but the ringing makes it a pain.. If i'm in front of the screen the notification on the upper right of the screen is enough to realize someone is calling, if i'm not, i probably have my phone with me.. if i m watching a video i'd like to be able to see that someone is calling but i don't need any sound for that... Is there a silence mode for FaceTime somewhere ?

The FaceTime preference's panel allows me to choose a ringtone but not to disable it... any help appreciated !

Have a nice day.