![]() That is, if the sound wave pattern of "blue noise" were translated into light waves, the resulting light would be blue, and so on. The color names for these different types of sounds are derived from a loose analogy between the spectrum of frequencies of sound wave present in the sound (as shown in the blue diagrams) and the equivalent spectrum of light wave frequencies. ![]() The Federal Standard 1037C Telecommunications Glossary defines white, pink, blue, and black noise. AR noise or "autoregressive noise" is such a model, and generates simple examples of the above noise types, and more. Various noise models are employed in analysis, many of which fall under the above categories. Note the slope of the power spectral density for each spectrum provides the context for the respective electromagnetic/color analogy. The power spectral densities are arbitrarily normalized such that the value of the spectra are approximately equivalent near 1 kHz. ![]() Simulated power spectral densities as a function of frequency for various colors of noise (violet, blue, white, pink, brown/red). For instance, the spectral density of white noise is flat ( β = 0), while flicker or pink noise has β = 1, and Brownian noise has β = 2. Many of these definitions assume a signal with components at all frequencies, with a power spectral density per unit of bandwidth proportional to 1/ f β and hence they are examples of power-law noise. Some of those names have standard definitions in certain disciplines, while others are very informal and poorly defined. Other color names, such as pink, red, and blue were then given to noise with other spectral profiles, often (but not always) in reference to the color of light with similar spectra. That name was given by analogy with white light, which was (incorrectly) assumed to have such a flat power spectrum over the visible range. The practice of naming kinds of noise after colors started with white noise, a signal whose spectrum has equal power within any equal interval of frequencies. This sense of 'color' for noise signals is similar to the concept of timbre in music (which is also called "tone color" however, the latter is almost always used for sound, and may consider very detailed features of the spectrum). Therefore, each application typically requires noise of a specific color. For example, as audio signals they will sound differently to human ears, and as images they will have a visibly different texture. ![]() Different colors of noise have significantly different properties. The lower the energy the light, the less work can be done with it by the atom when it absorbs that light.In audio engineering, electronics, physics, and many other fields, the color of noise or noise spectrum refers to the power spectrum of a noise signal (a signal produced by a stochastic process). Radio waves cause nuclear spin transitions which is when a proton changes its spin state. Microwaves cause rotational motion where a molecule rotates. The bonding atoms of a molecule vibrate back and forth like an oscillating spring. Infrared light causes molecular vibrations. The electrons are able to move between the energy levels within the atom, but do not have enough energy to escape. Low energy UV and visible light cause electron transitions. They transfer enough energy to electrons so they can escape from the pull of the atom’s nucleus and turn the atom into an ion. Higher energy light such as gamma rays, X-rays, and high energy UV light cause ionizations. And since energy and frequency are directly proportional, the trend we describe using energy will be the same for frequency. ![]() The different effects light has on atoms can best be understood when considering the energies of types of light. ![]()
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