on a hot summer day, when you're sitting out in a garden, and somewhere in the distance you hear the sound of - i never know what it is - some machine, perhaps a grassmower or someone sawing branches (chainsaw sounds so violent, but - sumpin like that) - anyway, often in the gardens you'll hear the whirr or burr somewhere invisible around, kinda just hovering in the heat. its really soothing.
also, the sound of leaves, trees .. even in the city, you take a walk and suddenly walk down a path, by the canal say, underneath the trees and you hear a rustle and a flicker of leaves .. brings instant calm back to you.
The falling of coins when I hit the jackpot playing the slots in Atlantic City.