I often hear two different audio sources simultaneously from my speakers. Yesterday, I heard what sounded like an AM radio announcer doing his thing and it didn't have any relevance to any website visited. Do I have a sound card problem?
No, but your machine has been possessed by a AM radio demon.... :lol: . .
Seriously though, most likely, you went to a web site that had a video autoplaying. If you run the Chrome browser (and probably some other browsers too), you should see a speaker icon on the tab of any page that is generating sound.