White noise basics
How white noise works
White noise works mostly by masking: it raises the background level, so sudden sounds stand out less.
White noise works mainly by sound masking. A constant, wide sound raises the background level, so sudden noises are less noticeable and less likely to wake or distract you. It may also give the brain a steady, predictable input to settle into.
Sound, frequency and power
Sound is vibration in the air. Pitch is how fast it vibrates, measured in hertz (Hz). A deep bass is about 50 Hz, a voice is mostly 100 to 4,000 Hz, and a hiss goes up to 10,000 Hz and higher. White noise has the same power at every frequency; pink and brown noise have more at low frequencies.
Masking: the main mechanism
When two sounds happen together, the louder or more similar one can make the other hard to hear. That is masking. A steady hiss does not remove the creak of a door; it makes the creak a smaller step above the background. Our brain responds to change, so smaller changes are less likely to alert us.
Why sudden noises wake us
During sleep, the brain keeps listening. It does not react to constant sounds but responds to sudden changes. In a quiet room, a car door is a big change. In a room with steady noise, it is a small one.
Predictability
A sound with no pattern gives the brain nothing to follow, and some researchers think steady sound can help some people relax. This is less well-established than masking.
Why babies react
Babies were exposed to constant sound before birth. See why white noise calms babies.
Limits
- It cannot mask very loud sounds.
- It masks sounds in similar frequency ranges best. Deep noise helps with rumble, bright noise with speech.
- It adds sound to the room, and that sound has its own safe level. See white noise safety.
Where it comes from technically
Random electrical fluctuations, such as thermal noise in electronics, are close to white. Generators like the one on this site produce random numbers to make a flat spectrum, then filter them for pink or brown noise.
Frequently asked questions
What is sound masking?
When a steady sound makes other sounds harder to notice.
Does white noise block sound?
No. It covers sound by adding to it. It does not block or cancel anything.
Is white noise the same as noise cancelling?
No. Noise cancelling creates opposing sound waves to reduce noise. White noise adds a steady sound.
This page is general information, not medical advice. Talk to your pediatrician about your baby's sleep and hearing, and follow current safe sleep guidance.