Audio running in the background

whenever I go to a post, audio starts playing in the background with people talking, as if a video was being played. However, I can’t find a video anywhere. Closing the browser tab then also stops the audio so I am sure it’s an issue with the Core77 site.
(Firefox 75.0 in Ubuntu 18.04)

Hello Bastian

Can you take a screenshot next time you hear the audio?