If you mute the chat in the upper right corner it will remember your setting on all future windows/tabs you open. If you are subscribed to multiple services, the mute doesn't carry over from service to service - you have to adjust volume once per service as users may want to get a ping on one service and not another at a given time.
You can also minimize the chat window next to the sound button - though this is required in each window/tab you have open. Many users have indicated that they prefer to have chat open in all their windows by default so 'they don't miss anything'.
Hope this helps.
Customer support service by UserEcho