I understand that sounds are not playing after updating to version 41. There was a patch that came out this week for version 41.0.1 that addresses plugin container hang, however I am not sure if that is responsible for the sound notifications. I would recommend starting here with these steps:

• What do do when Firefox does not Play Any Sound

Thanks for the response. Unfortunately, I had already tried the equivalent of those steps, by starting Firefox 41 in safe mode.

Note that sound in general works (eg, youtube) - its just alert dings. Presumably, these alerts go through some other OS service, and firefox 41 is disabling/muting that (though I have no idea what that service would be).

Did you check if Firefox (not Flash) was muted in the Windows Audio Mixer settings when on version 41? However, you seem to use Windows XP, so I’m afraid you won’t have a separate slider for Firefox, unless the issue occurs on a system with Windows 7 or up. Then again, it would be strange to see the slider going up by itself when restoring the previous Firefox version, but I’ve experienced such slider issue myself some versions ago.

I also wanted to point you to the What to do if Firefox won't play any sounds article mentioned above that explains this possible cause, but be sure to select Windows 7 on the left when viewing it in order to see the Mixer info when on Windows 7 or up..

However and when following the bottom link in that article pointing to Fix common audio and video issues, you’ll find the tip on allowing internet access to Plugin Container. That seems to make more sense, since reinstalling the previous version fixes it. I’m not sure why plugincontainer would affect internal FF sounds (only), but it may be worth a try to check any firewall or security software related settings (or remove them and allow that software to set them again when prompted). When at it, please check if acces to 127.0.0.1 is allowed as well.

Could you also try this test page for the built-in HTML5 audio player to see which formats are audible on your Firefox: http://hpr.dogphilosophy.net/test/

Thanks all for the help. I tried all of the above, but still no luck:

41.0.1 (I had tried 41.0 originally) still doesn't play alerts.

I checked all the audio-related things in the control panel and none of them are muted.

I removed and readded firefox as an exception to my firewall.

No sound in safe mode either.

None of the entries on the test page by jscher2000 produce any sound.

Like I said earlier, flash and other media pages work fine, but alert dings (for outlook webapp webmail, games) don't work.

Thanks

One other thought: a mute browser can be caused by Firefox sending audio output to a no-longer-available device, such as a headset or television. I haven't experienced that myself, but other users have reported that after reconnecting the missing device, they then could switch the audio back to computer speakers. Not sure if that is relevant to your situation.

Subash said

I removed and readded firefox as an exception to my firewall.

Did you do te same for plugin-container.exe?

Yes I did.

I was hoping the problem would just go away with the next Firefox, but the problem also exists on Firefox 42.

Thanks

Did you check the volume setting and the default sound device in the Windows Volume mixer (icon on Windows Taskbar notification area) while sound is playing?

Also in 42 there is a sound icon that shows up on tabs that are successfully sending sound, if its not the hardware/driver/operating system settings does that icon show up in the tab?