Naturespace [App Store] for the iPhone and iPod touch is a free app that lets you sample very natural and realistic sounds to relax to. They come from the folks at Holographic Audio Theater, who produce some very serene audio tracks for meditating, relaxing, or helping you sleep.
The app itself is attractive and easy to use. It provides 5 different audio environments for headphone listening. While there are some other nice apps that provide similar features, I thought this had the best audio and the most enveloping sound I had sampled. I especially liked the sound of waves lapping on a beach because of the gentle right to left movement.
I listened on both regular headphones, and iPhone earbuds. The software has a switch to turn earbud equalization on, and it did seem to deepen the bass and improve the realism of the presentation.
The app is very well thought out, and if you change to one of the other ambient recordings the sounds slowly fade down and then the new selection fades up. You can go to sleep using these sounds and turn on the iPhone sleep timer. The developers will be glad to sell you additional low cost ambient recordings, but the free app is not crippled in any way and has no advertising. The positive reviews at the App Store are a pretty good indication that this is a well conceived piece of software.
This app will be worth a couple of bucks to many people, but since it is free, I think it's a no-brainer to try and see if you get swept into the sonic environments that are provided. The loops are seamless, so there is nothing to interrupt your reverie as you s l o w l y... r e l a x... a n d... b e g i n... t o... n o d... o f f ...........
Here are some screen shots: