You possibly were getting some feedback through your speakers (static electricity or something else). We can't check your computer, but I'd say you just had some sort of feedback in your speakers, hackers don't make your speakers go boom.

My PC Tools stopped Spyware.Known_Bad-Sites and reading up on it I see that it will enable a hacker to take over your browser. It is sitting on PC Tools and I will remove it...... However I think the big boom was "thunder "from The Weather Channel application which I was using. I shut down my puter' and restarted it, when it reloaded The Weather Channel the thunder(boom) did it again. Good grief! this was not funny considering what is going on in Boston. I have uninstalled this application and also my Weather Bug, will consider some other weather program. Thanks for you help.