wow.... i just experienced the same thing seconds ago and out of desperete need of an explanation i googled this..
im actually doing my project for school right now that is due tommorow and ive been sitting in front of my computer for several hours of silence.
out of no where, my mind kind of wandered and my ears focused on the smallest noises. typing keys are like banging, and the sound coming from my computer booms. everything is magnifyed in perspective, and ringing within my head.