Very recently a couple of our systems have started making beeps on shutdown, we've not been able to isolate the exact time that they've been updated and it's occuring, but I've narrowed it down to being not pcspkr or snd_pcsp as both are blacklisted under modprobe, and rmmod'ed just to be sure. Now I'm a bit puzzled as I was under the impression those were the only two modules that could make the beep, is there a third lurking that I need to blacklist?

Edit:
I've copied the results of lsmod over on Pastebin.