Most Americans accept that the world around us -- with its traffic, electronics, and cell-phone conversations -- has made silence pretty rare these days. In his new book, "In Pursuit of Silence: Listening for Meaning in a World of Noise," George Prochnik writes that this noise is more than annoying, and is actually bad for your health. Ever-present background noise hurts our cardivascular system and our concentration, and turns our political discourse into a shrill barrage, writes Prochnik. He looks at different ways that noise intrudes on our lives, and even at how the peculiar pitch and volume of Hitler's voice may have been responsible for convincing Germans to support him.