Brownian noise

Brownian noise, also known as brown noise or red noise, is a type of background sound that includes a large quantity of low-frequency sounds. It is similar to the sounds made by waterfalls, heavy rain, low rumbling thunder, or a heavy wind. Brownian noise is generally considered to be very soothing. Some people claim that brown noise helps them relax or sleep more easily, although scientific evidence supporting its effectiveness for attention deficit hyperactivity disorder (ADHD), anxiety, or sleep disorders remains limited.

Background

Brownian noise takes its name from Scottish botanist Robert Brown (1773–1858). While studying pollen in water under a microscope in 1827, he observed that it appeared to move erratically, even though it had no means of movement. He recorded his observation, and later scientists named this type of random movement in his honor. Brownian noise is mathematically related to Brownian motion because its signal changes follow a random-walk pattern. In acoustics and signal processing, brown noise is defined as noise whose power decreases proportionally as frequency increases, producing a 1/f² spectrum. The name is often shortened to brown noise. Brown noise belongs to a category called colored noise, which includes white, pink, blue, and violet noise. Colored noise patterns are studied in acoustics, audio engineering, and digital signal processing. It is also sometimes called red noise because red light waves have longer wavelengths and lower frequencies than white light waves do, just as red noise has higher levels of low-frequency sounds than white noise.

Overview

People are often most familiar with white noise, which is a sound that combines all sound wave frequencies to create a noise resembling static, a fan or motor, or rustling leaves. Brownian noise is like white noise but contains higher frequencies at much lower intensity. This makes it sound lower, with a deeper rumble and bass tone. Digital audio systems often create brown noise by modifying white noise to increase low-frequency sound energy. It has been compared to the sound of a hard ocean surf, a heavy storm, or a large waterfall. Some people think it is more pleasant to listen to than white noise because its higher frequencies are less intense.

Machines that generate white noise to serve as a sleep aid have been around for many years. Some machines have also been developed that use other types of background noises, including those known as pink, blue, violet, gray, and black, as well as brown noise. Brown noise recordings are also available through smartphone applications, streaming services, and digital sleep-aid devices. While only a few scientific studies have been published on the possible effectiveness of Brownian noise in helping people sleep, many people claim that it does. Some researchers have suggested that background noise may help certain people concentrate by masking distracting sounds, but evidence specifically supporting brown noise remains limited. Brownian noise may help some people focus while studying or working, although scientific evidence remains limited.

In the summer of 2022, an account on social media that claimed listening to brown noise helped a person with ADHD and anxiety calm down generated a great deal of attention. The related video clip was viewed almost ten million times in a few weeks. Experts who commented on the situation said that while it was possible that brown noise could help situations like this, it was equally possible that there could be harmful effects and more study was needed. Brown noise is not approved as a medical treatment for ADHD, anxiety disorders, or sleep disorders.

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