White Noise: An Overview

White noise is a catch-all term used to refer to sounds which, by their nature, are capable of masking background noise in an environment. While it can be produced by a purpose-built white noise machine, white noise can also originate from an air conditioner, a bedroom fan, or radio static. As for how and why it works?

To understand that, we'll need to briefly go over the basic components of a sound wave.
  • Frequency refers to how many vibrations the sound wave experiences each second. The human ear can detect frequencies as low as 20 Hertz (Hz) and as high as 20,000 Hz. 
  • Amplitude measures the size of each sound wave, which is basically a fancy way of saying it determines how loud a sound is. 
What makes white noise unique is that it maintains equal amplitude across all audible frequencies. In that regard, it's somewhat similar to white light, which contains every visible color in the spectrum. With most sounds, you can make out individual sound waves when measuring them  — white noise, on the other hand, tends to look like a solid, jagged line.
Believe it or not, we're actually not entirely certain why white noise works the way it does. One theory posits that louder environments mean one's ears become less sensitive, and vice-versa. By using a white noise machine, you raise the sound threshold of your surroundings, making irritating sounds like barking dogs and car horns inaudible.
Another theory holds that the presence of a monotonous, steady stream of sound keeps the brain occupied without overwhelming it.

The Different Types of White Noise

Believe it or not, white noise actually comes in a few distinct flavors and categories, depending on its frequency and intensity. These include, but are not limited to: 
Pink noise
White noise that's softer at higher frequencies and louder at lower frequencies. There's evidence to suggest that if you listen to pink noise while sleeping, you may experience minor memory improvements.
Brown noise
White noise that's extremely quiet at the high end of the spectrum, and much stronger at the low end of the spectrum. It can help with relaxation and focus.  Brown noise has no relation to brown notes.
Violet noise
A unique type of white noise, known also as purple noise. Increases in volume at higher frequencies, and is particularly useful in treating tinnitus
Blue noise
Becomes denser as its frequency increases, leading to an increase in volume.

How White Noise Works

Complete silence, particularly if you live downtown, is usually impossible. Unfortunately, for light sleepers, this often means being woken up at inopportune times by the soundscape of your surroundings. A white noise machine counteracts this by giving your brain something to focus on while you rest, keeping it calm and preventing it from setting off alarms and waking you up at the slightest provocation.
As we've already noted previously, a white noise machine can also help reduce stress, soothe headaches and migraines, improve focus, and even help in tinnitus treatment. It's also seen regular applications in hypnosis. In addition to white noise machines, there are also several white noise apps on both Android and iOS such as White Noise Lite.
These apps generally allow you to choose from a few different 'brands' of white noise, depending on what you find most comforting. Options may include flowing water, waves on a beach, light wind, or the sound of a forest. Using them is as simple as downloading the app, plugging in your phone to charge, and activating it before you go to sleep.

White noise generators and white noise apps also tend to be popular among parents. Their effect tends to be particularly calming on infants and young children, as it's similar to the subtle sounds babies can hear from their mother's womb after the sixth month of pregnancy.

Parents who choose to use white noise machines should be incredibly mindful of volume and set them some distance away from their child.