Think of the sound you make when you let go after holding your breath for a very, very long time. Think of the gladdest sound you know: the sound of dawn on the first day of spring break, the sound of a bottle of Coke opening, the sound of a crowd cheering in your ears because you're coming down to the last part of a race--and you're ahead. Think of the sound of water over stones in a cold stream, and the sound of wind through green trees on a late May afternoon in Central Park. Think of the sound of a bus coming into the station carrying someone you love. Then put all those together.