This is an interesting clue. Does the issue occur on websites that are not broadcasting audio, or only if there is an audio component?
The first thing that comes to mind is some of the issues folks have been having with JamesDSP, such as in these other recent threads:
- Media Player & Firefox Freeze Until Volume Adjusted
- Problems with sound on garuda
- Videos not playing
Check to see if it is running on your system, and if you are not using it disable it or remove it.