
In a big city, silence is a luxury — second only to quality sleep. Wherever you live, though, white noise can make it easier to get both at once.
White noise is really just the combination of noises that are humming at different frequencies. What you end up with is a soothing kind of muddled nothingness (e.g. radio static). But when we say "white noise," we usually mean "ambient noise," of which white noise is one variety. You might have also encountered pink noise (think: steady rainfall or a bustling coffee shop) or the even deeper brown noise (think: a waterfall or traffic rumbling in the distance).
It makes a little more sense if you think about light: Light with a similar frequency pattern to pink noise, for instance, would appear pink. Same goes for blue and green noises. And white noise, like white light, is what you get when you combine all the other frequencies out there.
Brown noise, on the other hand, isn't named for its color (or pooping, sorry). Instead it's a reference to Brownian motion, a concept in physics that describes the way particles move around in fluid.
Essentially, all of these noises work by masking other potentially annoying sounds (hello, squeaky hallway door) and making them seem less alarming to your brain. That way, you can focus on your work or your ZZZs. Some people believe that certain types of ambient noise are better for certain tasks, such as playing coffee shop sounds in the background while you work and a fan while you sleep. And there is some evidence to suggest that pink noise might be particularly useful for sleeping.
But, overall, matching a specific noise to your activity seems to be a very personal thing. So, the best thing you can do is try a bunch of stuff out and see what works best for you. Continue on to see some of the most popular ambient noise machines and apps — and let us know what your favorites are!

This classic model — and its relatively reasonable price — have a ton of devoted fans.
Sleep Easy Sound Conditioner, $29.99, available at Amazon.

Free apps don't usually come with this many options — or with sound quality this great.
Tim Gostony Rain Rain Sleep Sounds, Free, available at iTunes.

With large dual speakers, this noise machine is great if your bedroom is large or you'd like to artfully place the machine on the other side of the room. (Yes, it comes with a remote.)
Homedics Deep Sleep II Relaxation Sound and White Noise Machine, $69.99, available at Amazon.

If you're not one for fiddling around with sound levels, Noisli might be perfect for you. The app's ready-to-go soundscapes (including a campfire, train tracks, and forest sounds) are comforting without being intrusive — and you can combine them!
Noisli Ltd Noisli, $1.99, available at iTunes.

This is the smaller version of the popular original LectroFan. Bonus: This one comes with nursery rhymes.
LectroFan LectroFan Jr., $35.96, available at Amazon.

One of the best-rated noise apps out there, myNoise offers some serious customization features.
myNoise BVBA myNoise, Free, available at iTunes.

Perfect for the sleepy girl on the go.
Marpac Rohm Portable White Noise Sound Machine, $34.99, available at Bed Bath & Beyond.
Like what you see? How about some more R29 goodness, right here?
Why This Group Is Handing Out Marijuana To Members Of Congress