Computers can do funny things in themselves. Are you absolutely sure that you didn't have an application running at the time that had silly sound effects? My husband was running Skype when I shut down our desktop pc the other night, and it let out a yawning sound - made me jump a bit!
Of course I'm not saying it was that, just trying to rule out non supernatural possibilities.
I remember being at my previous laptop one night, when all of a sudden there commenced several seconds of what sounded exactly like that of old fashioned typewriter keys being pressed, randomly and rapidly, just as if someone were typing. Now, I didn't have any sound scheme at all selected on the lap top - I never do, as I hate gimmicky sound effects, and I had the sound muted anyway. But this key clattering sound went on for about 15 or 20 seconds, while I sat staring at the laptop, cacking myself, crying, "uu-uu-uuhh -
stop i-iit!! 
To this day I don't know if it was the hard disk drive playing up that was causing it, or something less rational. But it didn't half freak me out at the time!
Linear Mode
