I cannot observe the problem here. I tested in virtual machines, 18.04 and 19.10, version 70.0.1 from the Ubuntu archive in both, and played with different values for the gain in your JSFiddle. When setting the value to 0 there is no sound to be heard.
Can you please run "apport-collect 1852645" ? ** Changed in: firefox (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1852645 Title: WebAudio API does not behave as expected (Cannot mute videos) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1852645/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs