Celestial (Free|$1.99, £1.49, AU$2.49) is an ambient noise app that claims to help you relax or focus, and it has a timer so you can listen while you fall asleep. Note that the free version comes with three sounds, and you can unlock three more via an in-app purchase, but if you buy the paid version you can skip this step.
The full version gives you six different ambient soundscapes that were recorded at real locations around the globe. Launch the app, select a sound type, press Play and melt away into your work or thoughts. Some design missteps that make the interface a bit confusing, but the sounds are of high quality, making the app worth your while.
Launching the app for the first time gives you the option to view a quick tutorial with a swipe to the left, or tap a button to dive right in.
The tutorial walks you through the basic premise of the app and how to navigate its various screens. It also recommends listening using headphones for the full effect.
After the tutorial, you're taken to a very minimalistic main screen -- a list of six different sounds, each with a photo to represent the sound's origin and a text label.
For example, the Focus listing has a picture of a highway full of fast-moving cars. Relax is accompanied by a photo of the ocean. The sounds range from white noise to "wind recorded during a Canadian winter," according to the App Store listing.
For me (and your experience will likely be different), the sounds all had the same effect -- they made me want to go to sleep. I didn't find one sound that made me more productive than another, which I admit says more about my lack of quality sleep than it does the app's ability to motivate me.
What's with the panoramas?
There's one feature in the app that seems out of place. When you're listening to a given sound, you'll notice the background picture moves as you move your phone. Pan to the right and the background moves with you. Move it to the left and the same thing happens in reverse.
I assume the goal here is to help someone relax by listening to the sound and feeling like he or she has been transported into a more soothing location.