before you start up machine turn sound all the way down. after machine boots turn sound back up. what happens? ( or shut sound off/down before you shut down..... that way on boot up they're off). it's the amp/power.
Its normal, happens on my Klipsch pro media 2.1 system as well, unless, as stated above, you turn the power all the way off on the speakers before you start the computer. Pretty sure that sound isin't damaging or anything