Maybe it’s a default setting now, but it wasn’t in my case, and I was getting super bugged by Edge sound notifications. I don’t actually use Edge much (Firefox being my preferred browser) but I have it open for some work stuff and any time some raises a ticket or replies to a ticket and if I have our ticketing system open it makes a ding sound. Of course I can mute the tab via Ctrl+M but sometimes I forget to and when I logout for the day I can still hear the browser making these ding sounds. Aargh.
Turns out there’s a hidden way of muting by default. Pop in this URL in Edge: edge://flags/#edge-sound-content-setting
Flip it from “Default” to “Enabled”, as in the screenshot. And then in Settings > Cookies and Site Permissions > you will now see a “Sound” section.
You can set it to be blocked by default and make exceptions, or enabled by default and block specific sites.
Thanks to this forum post where I discovered this.