I am getting the same problem. I've run malware and symantec scans and nothing has helped.

I believe it's being caused by the cool previews add-on. I have disabled it and it seems to have stopped.

This sound stops after turning off CoolPreviews.

Wow. I thought I was losing my mind. I heard that noise while I had about 8 tabs open. I didn't want to close them, so I bookmarked them all and closed them one by one. I finally got to the last one and closed firefox, and I thought I ran into the page that was making those silly sounds. Now it's just happening every time I start up. It is quite frustrating because I want to play Pandora radio, but can't with that annoying sound. AGH!

Disable your "Cool Previews" add-on. It stopped the problem for me.

Same stupid pacman noise here... hey! thanks mjr i'll try to remove cool-prev. ;)

Disabling Cool Previews worked for me too

If this is something that the users cannot disable, I will never use Firefox again! This is annoying as hell! Oh, and thanks for letting your users know about this, Mozilla! Even if this is just a one day thing, the fact that there was no heads up about this shows me that Mozilla doesn't really care what their users think...

Looks like I'm switching to Chrome...

CoolPreviews causes it....

same problem, just started today

I disabled CoolPreviews and restarted the browser. That stopped the problem.

Hope this is helpful. Looks like I may be trashing CP.

As "mjr" just did, I also disabled my "Cool Previews" add-on and that seemed to fix it. Thanks for the tip, mjr! You may have just saved my sanity for the day. :-)

uninstall Cool Preview, and the problem will go away!

What the heck??? How do I get rid of this????

disable "Cool Previews" = Silence , annoying stuff for a friday

I had the same problem and after looking at the posts here I took mjr's advice and uninstalled the CoolPreviews add-on. Everything's back to normal.

unistall cool previews and the annoying sound will go away

You don't have to uninstall Cool Previews entirely, just disable it. It appears by browsing to google.com, you can click on the Pac Man graphic and play the game. When you play, the sound plays. Evidently Cool Previews does something with that app to make it automatically start to play or something... I'm an applications developer, not a web developer, so I don't know.

Had the same problem. Unloaded Coolpreviews and problem went away.

AAA Firefox user

Yes, CoolPreview causes this. Turn it off.