You can scan the Billboard 100 from top to bottom and you won't find a listing for the day's chart-busting rain, ocean, and babbling brook sounds. But that doesn't mean there aren't listeners intensely interested in filling their ears with exactly that kind of audio. Whether to help lull you to sleep or block out the sounds of a tightly packed open office, ambient audio can be a useful tool. And, best of all, it needn't be confined to the tiny-speakered/tinny-sound consumer "sleep machines" you find advertised in the back of in-flight magazines. With an iOS device you can be wrapped in an otherworldly environment in seconds.
