Noise therapy for sound sleep

Over the last 20 years, scientists have uncovered evidence that immersive sounds like white, brown and pink noise may help the brain focus, sleep or relax. For people with standard hearing function, brown noise’s better-known and better-studied cousin, white noise, has a more hissing sound than brown noise. Pink noise is a softer version of white noise, playing lower frequencies a bit louder. Violet noise plays higher frequency sounds louder than brown noise and makes a hissing sound.

Scientists have reached conflicting conclusions on whether any particular type of noise can help you sleep better. A 2020 review of 38 studies found limited evidence that white noise can improve sleep, despite the prevalence of white noise machines marketed for sounder nights. Some companies promote white noise machines to help babies sleep, claiming the sound mimics the environment in the womb.

What is brown noise?

The human ear only detects sounds within a certain range of frequencies — those that stimulate the cochlea, a spiral-shaped cavity swirling in our inner ears. When we play brown noise, we hear every frequency that the ear can detect at once, said Dr Daniel Berlau, a professor at the Regis University School of Pharmacy who has studied the impact of white noise on A.D.H.D. Listening to all of these frequencies at once creates an immersive, even smothering, experience that some people may find pleasant, could relieve stress and soothe them to sleep.

Dr Berlau pointed out a simple theory for why people say noise begets sleep — be it pink, white or any shade. Sounds may block out your downstairs neighbour, the traffic and your partner’s snoring. And, experts said, if any form of noise therapy works for you, there’s no harm in using it.