# Noise Types and Colors

In this article we will have a look at some interesting and unknown aspects of noise. Noise is a random signal that accompanies not only sound, but also current, voltage, data etc. Therefore, noise is not merely an acoustic phenomenon but the fluctuation in a system as a result of internal or external sources. Noise could be static that can be heard on the radio or the white noise when there is no signal on the television.

### Types of Noise

There are two major categories of noise – frequency based noise and the non-frequency based noise. Frequency based noise consists of colors and its frequency matches a particular color frequency. Noise such as pops, crackle and snap are examples of non-frequency based noise. In general, there are three types of noise characterized according to their dependence on time. They are:

Gaussian Noise: This type of noise is not dependent on time and is therefore random. The amplitude of its frequency varies in an arbitrary manner.

Drift Noise: This type of noise is random but depends on time.

Shot Noise: This type of noise entails sporadic short bursts of noise. The amplitude of the noise remains the same at random intervals of time.

### Colors of Noise

While it may seem a little distant to correlate sound and color, there is a scientific basis to it. If the frequency of a particular noise corresponds to the light wave frequency of the color, the noise can be correlated to that particular color. Noise colors can be of the following types:

–       White Noise: A signal or process with a flat frequency spectrum corresponds to white noise. It is the only noise that can operate in linear space.

–       Pink Noise: It has a flat frequency but does not operate in linear space. Instead pink noise operates in logarithmic space.

–       Brown Noise: Here, the name Brown does not stand for the color per se. This type of noise is generated by a particular motion known as Brownian motion. Brown noise is often referred to as Red Noise as the frequency of the waves corresponds with red light waves.

–       Blue Noise: Also known as azure noise, the power density of blue noise increases by an amount of 3 decibels per octave as the frequency increases. This noise has a minimal low frequency without concentrated energy spikes.

–       Purple Noise: Purple or violet noise is a differentiated white noise.

–       Gray Noise: This type of noise is a random white noise that is equally loud at all frequencies.

### Unofficial colors

• Orange Noise: This type of noise has small zero energy bands spread through the continuous spectrum.
• Green Noise: It is the background noise of the world.
• Black Noise: This type of noise is also known as the silent noise and is often considered as ultrasonic white noise. Black noise is itself not silent but cancels out other noises in a limited space to generate silence. According to some researches, black noise accompanies natural disasters such as floods, etc.