There is an option in the Settings -> Notifications, when. When you go to section "group"Group notifications", there is an option to set the notification tone, vibrate or Popuppopup notification. I did it for
In my "groups" cuz its annoying to have your phone vibrating all the time cuz two from 20 people are using group conversation instead of private one... Socase, I've just turned ofoff the vibration and set tone to "no sound" and itsit's fine for me.