Play this marvellous video (thanks MikeTaylr!) WITH SOUND then click the button to set display:none while it's playing.
TL;DR, the audio keeps playing. I think this is a bug; if something is not displayed to the eyes, it shouldn't be displayed to my ears.
It's related to a Chromium bug I raised when trying to use HTML popover as a 'lightbox' for images and video viewing, which to me is an obvious popover use case.