To understand how white noise helps you sleep, we need to take a quick step back and look at how sound and hearing work first. The sound is a wave that moves through the air, vibrating molecules as it goes along. The vibrations hit the eardrums then pass through to the inner ear where cells called hair cells change the vibrations into electrical signals. These signals travel to the brain and tell you what sound you’re hearing. The frequency of that wave – technically speaking, how often the particles vibrations repeat in one second – is measured in Hertz. Humans can hear sounds from 20 Hertz to 20,000 Hertz, and the higher the frequency, the higher the note you hear, and also the less easy it is to ignore. And these hearing faculties still work when you’re sleeping.
Even if you’re not awake, your brain can register significant sounds. So when you hear a noise at night, and it wakes you up, it’s the sudden change in frequency of background noise that disturbs your sleeping brain.
So how can you stop those sudden frequency sound from ripping you out of dreamland? Here comes the white noise.
White noise, properly speaking, is a constant noise that covers all hearable frequencies at once at a constant power rate per Hertz. Its frequency spectrum is entirely flat so that no new sounds can be heard over it – if it is playing loud enough, of course. White noise substantially masks all other sounds. And that’s where it gets its name.
White noise is analogous to white light. White light is all wavelengths of light, and white noise is all frequencies of sound. Because it is characterized as constant noise with equal power across all frequencies, that means some sounds that people call white noise aren’t. The hum of an airplane engine, for example, or the pitter patter of rainfall. They’re soothing sounds that block out some noise, but they aren’t true white noise.
White noise isn’t the only color of sound. There are others and like how colored light is a particular wavelength, colors of sound focus on specific frequencies. And some research suggests that pink noise is a better sleep sound than white noise. Like white noise, pink noise contains all frequencies audible to human ears, but the power per Hertz decreases as the frequency increases. It’s a subtle difference.
In a small study of 11 subjects, a team of German researchers played pink noise in synchronicity with sleeping subject’s brain rhythms. When compared to a control that had no sound stimulation, the pink noise seemed to prolong deep sleep and enhance memory retention in the morning.
There are other colors of noise too, corresponding to different frequencies like how colored light focuses on different wavelengths. There’s red or brown noise, blue noise, violet, black, green, and orange noise, though there’s no evidence about how well they might help you sleep.
So why do we find white noise soothing? Well, it’s a personal preference thing. Some people love white noise, and some hate it, but most people find it helpful for sleep because of its ability to mask other sounds. Don’t we all want a nice, quiet night’s sleep?
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