white sphere with 3 triangular-shaped points, made loud humming/ringing noise

I was in the 5th grade, the whole school was outisde during lunch.  I heard a loud ringing noise.  Everybody heard it.  The sound was like when the TV stations used to go off the air and show the colored bar symbol, or the Indian Chief.  I looked up, and alomost diredctly overhead, perhaps a mile high, was this white spehere with 3 points on it - north, east and west.  This is exactaly how it appeared to me.  Picture a circle with three triangular points.  It looked like Sputnik, only it was hovering in the air for all to see, amd it moved very slowly across the sky, making this constant humming/ring.  It was a high pitched sound.  The sound was constant, no other tone sounds, no pulse to it, no rythm.  I walked up to the vice principal of the school and asked him, "What is that thing?"   He looking at it too... He said "I don't know".  After several minutes it just moved out of sight.  It was hard to tell if it was changing altitude, moving higher.  Somtime later, in class, we heard the ringing sound again.   We did not go outside to investigate, and the sound did not last very long.
Witness indicates that the date of the sighting is approximate.  PD