Brown noise is a type of sound signal that contains a mix of frequencies, with more energy at lower frequencies. It is named after the Brownian motion, which describes the random movement of particles. Brown noise sounds deeper and softer than other noise types, like white noise or pink noise, making it popular for relaxation and sleep. Many people use brown noise to mask background sounds, helping them focus or fall asleep. It can be found in various applications, such as sound machines and smartphone apps, providing a soothing auditory environment for those seeking calmness or concentration.