Its just a chat sound you can turn off. But it has made the chat significantly more active since putting it in. It makes it easier for people to bump into each other and makes it much more likely you will get a response if you say hi.
It can be seen on pretty much any page (if signed in)
Or full window chat:
https://matrix.gvid.tv/chat
Come say hi!
https://matrix.gvid.tv
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