Hi Indy1829,

I'd try starting Firefox in Diagnose Firefox issues using Troubleshoot Mode and disabling all the plugins but the one playing the audio. If you don't have the issue while all of your other add-ons, extensions, and themes are disabled, you can try adding them back in one by one until you find the culprit. You should look at the Extensions and Themes troubleshooting guide and the Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems article as well.

You can find more information on this issue in this thread:

https://support.mozilla.org/en-US/questions/749114

Hopefully this helps!

This can also be caused by a problem with the plugin-container process that doesn't close properly and keeps running.

• http://kb.mozillazine.org/Plugin-container_and_out-of-process_plugins

i'm using Nightly, after tried disable all add-ons then re-enable 1 by 1, i found out there is a problem with flashblock o.O although i updated the latest version, it's still not change a bit.