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What are the Different Colors of Noise

What are the Different Colors of Noise

Colors are not just about what you see around you or what you paint. It is something that creates an activity or provokes a reaction. And if you happen to study physics of sound, you might be stunned to know that sounds and colors are related.
Anuja Marathe Kanhere
In Physics, noise has been popularly defined as a disturbance, especially a random and persistent disturbance, that obscures or reduces the clarity of a signal. It is a known fact that white color consists all the colors that can be seen. This holds true in case of sound too, where white noise gets created when sounds of different frequencies reach one's ear. Noise levels and frequency can be charted graphically using the various appropriate colors. The technique of spectral density is used for differentiating noises. This technique is popularly used in fields of electrical engineering and acoustics.

One of the basic noise model used for reflecting the colors of noise is known as Auto-regressive noise model. Colors of noise come in all shades of a rainbow. However, some popular colors of noise include white, pink, red/ brown, blue, green, gray and black. Many physicists assume that there are noise signals with components at all frequencies with a spectral density per unit of sound bandwidth equal to 1/fβ.

Different Colors of Noise

White Noise: The spectral density of white noise can be obtained by putting β=0 in formula 1/fβ which creates a flat spectrum on frequency graph. The sound power of white noise is same at any level of frequency. It is most commonly created in scenes of chaos where it is impossible to perceive a single person's sound or voice. This technique of white noise is commonly used in alarm systems, amplifiers and electrical filters, tinnitus maskers or sound maskers, privacy and sleep enhancers, etc. White noise mechanism is used at times to induce concentration.

Pink Noise: Pink noise is said to lie in between white and red noise. The power density of pink noise falls off at the level of 13 dB per octave or 1/f. For this reason, pink noise is often referred to as 1/f noise. The spectral density of pink noise can be obtained by putting β=1 in formula 1/fβ. Every octave of pink noise contains an equal amount of energy and therefore it is popularly used in sound engineering techniques.

Red Noise: Red Noise is also known as Brown Noise. It usually refers to power density that decreases with increasing frequency. The spectral density of red/ brown noise can be obtained by putting β=2 in formula 1/fβ. The frequencies generated during red noise are said to have a soothing effect and are therefore used to create a relaxing environment and to induce sleep.

Blue Noise: The Power density of blue noise is said to rise at a rate of 3 dB per octave over a finite frequency range. Blue noise is considered ideal for dithering, which is an essential step in music recording. It is also said that retinal cells by nature are arranged in blue noise pattern. This creates a good visual resolution.

Green Noise: With a long-term power spectrum, green noise is considered to the background noise of the whole world. It is soothing in nature and is considered ideal for creating meditative environment.

Gray Noise: When a listener perceives the noise to be equally high at all frequencies, it is usually known as gray noise. In reality though, the frequencies of a gray noise make an inverted A-weighting curve.

Black Noise: Silence is often termed as black noise. The frequency spectrum of black noise is most of the time null, with an exception of some thin bands and spikes. Black noise has been commonly associated with natural calamities such as floods, earthquakes and droughts. Black noise can be denoted with a 1/fβ where β>2.

Colors of noise is a highly technical field that makes a co-relation in fields of sound and color. It is a concept difficult to grasp and comprehend when you begin, however one can gain an expertise in this field gradually. My article is just a tiny input on this subject. I hope this article satisfies your curiosity about the subject and triggers your curiosity to explore more in this field.