Oh yeah, when I was just a little kid, as I was trying to go to sleep I would see a white background and it would sound as if a thousand violins were playing a group of notes in perfect harmony, with just enough high notes to keep me relaxed, but on edge. The noise gradually grew quieter and quieter until I could just barely hear it, and then they would all BLAT, but still in harmony. Now, I'm pretty sure it was some intence HI and sound, but oh man, it would jerk me out of my relaxed state really quickly.