Within Earshot

How far can the human voice travel? Can one's call of distress reach the ears of God?

Have you ever used the expression "within shouting distance"?

It's an idiom that means "fairly close" or "near," as in, "I live within shouting distance of my parents." We take that to mean that they live just down the street from you or only a few blocks away or nearby. While we might not always mean the phrase literally, the idea is that if you went outside and shouted for them, your parents would be able to hear you.

But how far, really, is shouting distance? According to the Guinness World Records, the normal intelligible outdoor range of the male human voice in still air is 590 feet 6.6 inches. Guinness adds that Silbo Gomera, which is the whistled language of the Spanish-speaking inhabitants of the Canary island of La Gomera, is, under ideal conditions, intelligible at 5 miles and that there is a recorded case, under optimal acoustic conditions, of the human voice being detectable at 10.5 miles across still water at night.

And why do we shout anyway? Unless you're talking to a...