When I play youtube videos, there is a dual audio track that can't be shut down, turned off, or volume controled. It plays in sync sometimes, but mostly starts late and sounds like an echo or worse! I have tried opening Firefox in safe mode but it does not solve the problem. So far it only happens with Youtube videos. I don't know if it's a Mozilla or youtube issue. There is also a small black 'speaker cone' icon it the right-hand side of the page-tab. If I click on it a strike thru line appeard over the icon to indicate it's been shut off. But it also closes down the other audio stream so there is NO audio at all! How do I fix this? Thank You