"Quiet, Gordon Hempton says, is a 'think tank of the soul.' The acoustic ecologist has criss-crossed the world searching for and recording some of nature's most elusive sounds. He says the experience of silence is in danger of being lost and explains why nature's 'silence' is vital to our minds, our relationships, and the natural world as well. He walks us through those environments — from the Hoh Rain Forest to thunder in the Kalahari Desert."
Producer/Host Krista Tippet interviews acoustic ecologist Gordon Hempton on American Public Media's 'On Being' May 10, 2012. 
Noise Control Act (Wikipedia)
Noise Pollution (US-EPA)