See: http://support.mozilla.com/en-US/kb/No%20sound%20in%20Firefox <br /> --------------------------- <br /> '''Other issues needing your attention''' The information submitted with your question indicates that you have out of date plugins with known security and stability issues that should be updated. To see the plugins submitted with your question, click "More system details..." to the right of your original question post. You can also see your plugins from the Firefox menu, Tools > Add-ons > Plugins.<br /> <br /> *Next Generation Java Plug-in 1.6.0_20 for Mozilla browsers #'''''Check your plugin versions''''' on either of the following links': #*http://www.mozilla.com/en-US/plugincheck/ #*https://www-trunk.stage.mozilla.com/en-US/plugincheck/ #*'''Note: plugin check page does not have information on all plugin versions''' #'''Update the [[Java]] plugin''' to the latest version. #*Download site: http://www.oracle.com/technetwork/java/javase/downloads/index.html (Java Platform: Download JRE) #**'''''Be sure to <u>un-check the Yahoo Toolbar</u> option during the install if you do not want it installed. #*Also see "Manual Update" in this article to update from the Java Control Panel in Windows Control Panel: http://support.mozilla.com/en-US/kb/Using+the+Java+plugin+with+Firefox#Updates #* Removing old versions (if needed): http://www.java.com/en/download/faq/remove_olderversions.xml #* Remove multiple Java Console extensions (if needed): http://kb.mozillazine.org/Firefox_:_FAQs_:_Install_Java#Multiple_Java_Console_extensions #*Java Test: http://www.java.com/en/download/help/testvm.xml

The recent update to Adobe Flash 11.3 is causing no sound for some Firefox users. See this thread for help. http://forums.adobe.com/message/4483563#4483563?tstart=0

I had the same "no sound" problem with Firefox 13.0.1. Also, I had the latest flash player plugin. I completed removed the flash player plugin. I re-installed older flash player version 10, file name: flashplayer_10_plugin_debug.exe, now the sound is back and perfect.