There are lots of apps out there with sound effects meant to soothe you to sleep, to help you concentrate, or to simply drown out the noise around you.

Few are as customizable as A Soft Murmur. A Soft Murmur can be used in any browser, or if you want to take it with you on the go, you can take advantage of the free Android app. Unfortunately, there is no iOS version of the app, but it's said to be in the works.

So what sets the service apart from others in its category? You can completely customize the sound that you're going to hear, and it couldn't be easier to use. As of now, you can choose from the sounds of rain, thunder, waves, wind, a crackling fire, birds chirping, crickets, a coffee shop, a signing bowl, and white noise.

You can choose to listen to just one of these sounds or you can combine them. So, for example, rain plus thunder plus crickets makes for a great combination to fall asleep to. If you just need some background noise to get you into a novel-writing mood, maybe the lone crackling of fire will do.

Not only can you choose which sounds to turn on, you can adjust the volume of each one. So if you prefer the sound of distant thunder, just turn the rain volume up and turn the thunder volume down.

What's your favorite tool or app you use to help you concentrate or fall asleep? Let us know in the comments.