Go into Tools -> Options -> Notifications. Find the specific notifications you want to disable, double click on the entry and more options within that category will appear. Anything you don't want to receive a notification for ,check/uncheck the boxes. Press Ok or Apply if you want this to be permanent. Alternatively, you can select the "Sounds deactivated" soundpack for complete silence. We tried to make this as customizable as possible, so you can decide for yourself to listen to all sounds, none or only selected ones.