I have the same problem but I think it is a combination of cool preview and flash. When I uninstall flash it goes away as well. Strangest computer glitch I've ever encountered. (running win7)

I have the same thing. Drove me nuts till I found this forum topic and disabled Cooliris Previews, and then the irritating fire alarm sound stopped.

I just checked the Cooliris Preview site and they're aware of the bug and have provided a new version 3.1 to fix it: http://www.coolpreviews.com/firefox/issues_cp_ff.php

thanks for the tip. I disabled Cool Previews and have no noise. Has anyone reloaded cool previews .... I'm gong to try that  :)

same problem here. windows XP.

cool previews just disabled and the noise seems to be gone.

Change the page to something else! Google's banner is a Pacman game which includes audio. Once you change the website, the sound will stop!

Finally, I appear to have solved the problem in a easier way (after being annoyed for many hours by pacman sounds). I discovered that I had a browser tab set to Google.com, one of four or five I keep as a kind of default. I also have a browser tab set to Google on IE--that's why I was hearing the blasted stuff there. When I closed those tabs, the sound was gone. At last. Thankfully. Blessedly. Gone.

I HAVE THE SAME PROBLEM WITH FOX FIRE ON TOO MUCH NIGHT TRAIN....ANY ONE KNOW WHAT IT IS? I TOOK OFF BOTH COOL IRIS ADD ONS SO DONT KNOW WHICH ONE. I HAD TO RE START THE BROWSER IN ORDER TO MAKE IT STOP

I'm on a MAC using Snow Leopard and I have the same issue. Very annoying! I don't have cool preview. Tried restarting, unplugging everything. Apple says it's a google thing and they'll figure it out. I hope SOON. It doesn't happen in Safari - just Firefox

OMG! whats wrong really1 i freaked out thought its a virus,,, comeeee on firefox THIS IS EMBARRESSIN.........

On a mac, Just turn of Cool Preview and noise gone. Thanks god for that. Just started on 24:00, nice virus on the net.

So I uninstalled Cool Previews, restarted Foxfire...noise gone. Then I reinstalled Cool Prviews...which must be the new version someone referred to...and all is good! Peace :)

Well, I uninstalled Cool Previews, but now when I go to the site to download and reinstall it, I can't find Cool Previews. Where did you find it?

it is a virus no matter what they want to say about pac man and 30. some trojan attached to some exe or other by a childs mind. all that noise out of nowhere is nothing more than a pointless irritation and possibly worse. probably had something like mcaffee or norton install it in an update too or better, microsoft update as that is when it happened to my machine, right after the update as do other things but they are usually called conflicts from security updates, this was probably with java. no one will claim responsibility either. that will be it for firefox for some time on my computer but the same kid brained jerks probably have something in mind for IE too. cool prev stopped working in that a few times already

Read this from CoolPreviews website:

BUG ATTENTION (PLEASE READ): MAY 21, 2010

Hearing music and Pac-Man music when you load up Firefox with CoolPreviews enabled?

Update: We just released Coolpreviews v.3.1.0521, which fixes the issue. It may take a couple of hours for the Mozilla servers to display the new version here on this webapage. If you don't see the new version here, we also have the fix at http://www.coolpreviews.com/.

The bug came about through today's Google's homepage, which automatically starts a Pac Man game after 5 seconds (go to http://www.google.com/ to see it). We had an old line of code that would load up the Google homepage in the background. We have now removed that code. Previously, Google did not have any music on their page. So, obviously, today's debut of Google music and games caught us with our pants down.

We apologize for the bug and the inconvenience it has caused. The bug came about through today's Google's homepage, which automatically starts a Pac Man game after 5 seconds (go to http://www.google.com/ to see it). We had a line of old code that would load up the Google homepage in the background. We have now removed that code. Previously, Google did not have any music on their page. So, obviously, today's debut of Google's mighty ghosts and sounds of Pac-Man caught us with our pants down.

Again, we apologize for the craziest bug we've ever experienced!