White noise, also called white sound, is not a “noise.”
White noise is actually a sound frequency or a signal that one hears as a gentle hiss, similar to the sound of wind rustling through trees, a waterfall, radio static or the ocean surf. To use a simple analogy, the color white contains the whole spectrum of colors of light. Similarly, white noise is created by using the entire spectrum of frequencies the human ear can hear.

How does white noise help me relax or work as a sleep aid?
Life is full of disruptive sounds and noises. Unlike playing music in such instances, white noise does not add to the clamor of noise. Instead, white noise contains equal frequencies of all sounds. Research has shown that a steady, monotonous stream of the same peaceful sound, such as white noise, can filter and mask distracting noises. This gentle continuous sound promotes a calm mood to help you relax and/or fall asleep.

Is white noise good for babies, especially for reflux/colic?

Absolutely.

The same soothing sonic benefits of white noise are quite effective in creating the right ambience for both parent and child to enable a safe yet natural sleep. Baby white noise CDs are particularly helpful in calming fussy or unsettled babies with tummy troubles. In fact, children under age 5 (and their harried parents!) can benefit from white noise.

Can’t I just run a fan, vacuum cleaner or other motor sounds to create white noise?

Well you can do – it will work to an extent. When you run an actual machine or motors such as vacuum cleaners, fans or blow dryers, all you get is noise; whereas white noise is a sound frequency. Pure white noise combines all sound frequencies together, with equal values of low frequencies all the way up to very high frequencies.