At the top right of a chat room, just above the room title, there is a speaker icon. Clicking on this icon brings up the settings for "Sound notifications":
Currently, a change to this setting affects all chat rooms. Selecting "visible room" means that an audio notification is given for any activity in any room that is currently open in a browser tab (regardless of whether that is the active tab).
It would be useful to be able to adjust audio notification settings for individual rooms. For example, The Nineteenth Byte is quite a busy room, so I'd like to be notified only when mentioned. The Cornell Box is a much quieter room, and I'd like to be notified any time there is activity regardless of whether I am mentioned. Currently I can set all rooms to notify me of any activity, or I can set all rooms to notify me only when mentioned, but I can't choose a different setting for each room.
This would also be particularly useful when setting up a room for a very specific purpose, such as discussion of a particular question.