White noise, black noise, brown noise, green noise, and pink noise are all terms used to describe different types of sound signals that have specific characteristics in terms of frequency content and amplitude.
White Noise: White noise is a signal that contains equal energy at all frequencies within a specified range, typically spanning the entire audible frequency spectrum. It has a flat frequency response, meaning that every frequency has an equal contribution to the overall sound. White noise is often described as a "hissing" or "static" sound.
Black Noise: Black noise is a term that is sometimes used to refer to complete silence or the absence of sound. It is the opposite of white noise, where there is no energy at any frequency.
Brown Noise: Brown noise, also known as red noise or random walk noise, is a signal with a power spectrum that decreases by 6 dB per octave as the frequency increases. It has more energy in the lower frequencies and is characterized by a deep rumbling or low-frequency sound. Brown noise is often used in audio engineering and relaxation techniques.
Green Noise: Green noise is not a widely recognized term in the field of acoustics. It doesn't have a specific definition or standard characteristics like white, pink, or brown noise. It's possible that it may refer to a specific type of noise used in certain applications or be a colloquial term used in a particular context.
Pink Noise: Pink noise is a signal that has equal energy per octave, meaning it has more energy in the lower frequencies compared to higher frequencies. It has a power spectrum that decreases by 3 dB per octave. Pink noise is often described as a "rushing water" or "rainfall" sound. It is commonly used in audio testing, sound masking, and sleep aids.
It's worth mentioning that these terms can sometimes be used inconsistently or have alternative interpretations in specific contexts. The characteristics and definitions of noise colors may vary depending on the field of study or application.