In science, and especially in physics and telecommunication, noise is fluctuations in and the addition of external factors to the stream of target information (signal) being received at a detector. Science (from the Latin scientia, meaning " Knowledge " or "knowing" is the effort to discover, and increase human understanding Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. In the fields of communications, Signal processing, and in Electrical engineering more generally a signal is any time-varying or spatial-varying quantity In communications, it may be deliberate as for instance jamming of a radio or TV signal, but in most cases it is assumed to be merely undesired interference with intended operations. Natural and deliberate noise sources can provide both or either of random interference or patterned interference. Randomness is a lack of order Purpose, cause, or predictability Only the latter can be cancelled effectively in analog systems; however, digital systems are usually constructed in such a way that their quantized signals can be reconstructed perfectly, as long as the noise level remains below a defined maximum, which varies from application to application. An analog or analogue signal is any continuous signal for which the time varying feature (variable of the signal is a representation of some other The term digital signal is used to refer to more than one concept In Digital signal processing, quantization is the process of approximating a continuous range of values (or a very large set of possible discrete values by a relatively-small
More specifically, in physics, the term noise has the following meanings:
- An undesired disturbance within the frequency band of interest; the summation of unwanted or disturbing energy introduced into a communications system from man-made and natural sources. Frequency is a measure of the number of occurrences of a repeating event per unit Time. A band is a small section of the spectrum of Radio communication frequencies, in which channels are usually used or set aside for the same In Telecommunication, a communications system is a collection of individual communications networks transmission systems Relay stations
- A disturbance that affects a signal and that may distort the information carried by the signal. In the fields of communications, Signal processing, and in Electrical engineering more generally a signal is any time-varying or spatial-varying quantity Information as a concept has a diversity of meanings from everyday usage to technical settings
- Random variations of one or more characteristics of any entity such as voltage, current, or data. Debt AIDS Trade in Africa (or DATA) is a Multinational non-government organization founded in January 2002 in London by U2 's
- A random signal of known statistical properties of amplitude, distribution, and spectral density. In Statistical signal processing and Physics, the spectral density, power spectral density ( PSD) or energy spectral density (
- Loosely, any disturbance tending to interfere with the normal operation of a device or system.
Noise and what can be done about it has long been studied. Claude Shannon established information theory and in so doing clarified the essential nature of noise and the limits it places on the operation of electronic equipment. Claude Elwood Shannon (April 30 1916 – February 24 2001 an American Electronic engineer and Mathematician, is "the father of Information Information theory is a branch of Applied mathematics and Electrical engineering involving the quantification of Information.
In some cases a little noise may be considered advantageous, allowing a dithered representation of signals below the minimum strength, or between two quantization levels. Dither is an intentionally applied form of Noise, used to randomize Quantization error, thereby preventing large-scale patterns such as contouring that are more objectionable This is especially true for signals intended for human appreciation, since the brain seems to expect signals to contain a degree of noise. See, for example [1]
See also
- Electronic noise
- Colors of noise
- Signal-to-noise ratio
- Noise level
- Noise power
- Noise-equivalent power
- Phase noise
- List of noise topics
- Audio system measurements
This article contains material from the Federal Standard 1037C (in support of MIL-STD-188), which, as a work of the United States Government, is in the public domain. Electronic noise is an unwanted signal characteristic of all electronic circuits. Even though Noise is a random Signal, it can have characteristic statistical properties Signal-to-noise ratio (often abbreviated SNR or S/N) is an Electrical engineering concept also used in other fields (such as scientific Measurements In Telecommunication, noise level is the Noise power, usually relative to a reference In Telecommunication, the term noise power has the following meanings The measured total Noise per bandwidth unit at the Input Noise-equivalent power (NEP is a measure of the sensitivity of an optical Detector or detector system Phase noise is the Frequency domain representation of rapid short-term random fluctuations in the phase of a Wave, caused by Time domain instabilities This is a list of Noise topics. Engineering and physics 1/f noise A-weighting Ambient noise level Audio system measurements are made for several purposes Designers take measurements so that they can specify the performance of a piece of equipment Federal Standard 1037C, entitled Telecommunications Glossary of Telecommunication Terms is a United States Federal Standard issued by the General Services Administration MIL-STD-188 is a series of US military standards relating to Telecommunications Purpose Faced with “past technical deficiencies in telecommunications A work of the United States government, as defined by United States copyright law, is "a work prepared by an officer or employee of the U The public domain is a range of abstract materials &ndash commonly referred to as Intellectual property &ndash which are not owned or controlled by anyone
External links
- Noise and Operational Amplifier Circuits (PDF) — Analog Devices Application note
- Calculation of thermal or Johnson noise, Nyquist noise - Noise voltage in microvolts, and noise level in dBu and dBV
- PEAR Lab: consciousness - machine interaction research using diode Johnson noise
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