Thanks, John, for putting this in terms even I could follow. Makes perfect sense, and ear tones don't seem to follow this rule.

I do have a question. You say , "twice as far from the source of a disturbance" which is kind of vague unless you specify km or mi. Still, I get what you are saying for the most part. Your (4*pi*radius*radius), however, left me appropriately humbled.

Cathryn

Cathryn