I made an update on this last week which should mean that sounds are working again more frequently in the browser:
https://github.com/discourse/discourse/commit/de08ce8f7b2d446511f12adee3b0f5495d37cf42
I still plan to make some enhancements around chat sounds. I think only having chat sounds when there is badge (green/blue dot) on the chat icon would be an improvement, as currently chat attempts to play sounds any time a new message is posted in channels or DMs you are in.