You know, there was once a Star Trek episode where Data reported an explosion with a volume of someething like 4x10^23 decibels... forgetting not only that sound doesn't travel in space, but that decibels are already a logarithmic scale...
Though I suppose it would be possible for a sound that loud to travel through space... remember, space isn't REALLY empty, there's the minute amount of interstellar hydrogen, as well as the constant quantum fluctuations of matter and antimatter being created and destroyed out of nothingness... so if you hit a molecule of hydrogen REALLY hard and it shot over a few kilometers and hit the next molecule of hydrogen, which just happened to hit another molecule of hydrogen, I guess you could call that a "sound wave"
Actually, I suppose a sound of any volume would travel through space, because there's no friction to stop the hydrogen molecules from moving until they hit something... the sound would just travel VERY slowly!
