Physics and Perception

If a tree falls in the wood and no one hears it, does it make a sound? Some people consider this to be a philosophical question, but to Fiorella, it is pure physics.

Think about it.  What causes sound--something coming in contact with something else.  If Fiorella  goes outside, she can hear the wind rustle the trees.  Inside, if she tries to to play her violin (laugh, chortle), the bow scrapes the strings. Even small motions produce sounds--Fiorella suspects that atoms emit a tiny squeak of horror when they splat against each other.

"Sound," according to Fiorella's analysis, is what we call our perception of this event, this contact between two entities. But what sort of things are happening in our universe that we don't have the physical equipment to perceive?