I haven't experienced the problem. Others have 'fixed' it by disabling hardware acceleration.

I haven't experienced the problem. Others have 'fixed' it by disabling hardware acceleration.

As far as I know, I'm not using any acceleration.

It is uncovered if you untick/uncheck "Use recommended performance settings" on the General page of Settings.

It is uncovered if you untick/uncheck "Use recommended performance settings" on the General page of Settings.

Thank you, but even though I deselected acceleration, firefox is still as quiet as a tomb.

I often forget the mute button on a video (screenshot). This article may shed some light: https://support.mozilla.org/en-US/kb/fix-common-audio-and-video-issues

I often forget the mute button on a video (screenshot). This article may shed some light:

First thing I checked, as said in the original post. And I read that article, as suggested by this help page before I could post.

Regardless, I've since found an excellent solution: transferring all browser data to Chromium and uninstalling Firefox.

Cannot replicate the issue.

Try downloading a separate copy of Firefox and run it from the folder(do not sign into you Firefox account) to see what happens.

https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

I omitted to mention earlier that you need to restart after disabling hardware acceleration. https://support.mozilla.org/en-US/kb/forum-response-disable-hardware-acceleration