In common use, the word noise means any unwanted sound Sound is a travelling wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations. In both analog Analogue electronics are those electronic systems with a continuously variable signal. In contrast, in digital electronics signals usually take only two different levels. The term "analogue" describes the proportional relationship between a signal and a voltage or current that represents the signal. The word analogue is derived from the and digital electronics Digital electronics are systems that represent signals as discrete levels, rather than as a continuous range. In most cases the number of states is two, and these states are represented by two voltage levels: one near to zero volts and one at a higher level depending on the supply voltage in use. These two levels are often represented as "Low&, noise is an unwanted perturbation to a wanted signal; it is called noise as a generalisation of the audible noise heard when listening to a weak radio Radio is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Information is carried by systematically changing some property of the radiated waves, such as transmission. Signal noise is heard as acoustic noise if played through a loudspeaker A loudspeaker is an electroacoustic transducer that converts an electrical signal into sound. The speaker moves in accordance with the variations of an electrical signal and causes sound waves to propagate through a medium such as air or water; it manifests as 'snow Noise in analog video and television is perceived as a random dot pattern which is superimposed on the picture as a result of electronic noise and radiated electromagnetic noise picked up by the receiver's antenna—it is the "snow" which is seen with poor analog television reception or on VHS tapes' on a television Television is a widely used telecommunication medium for transmitting and receiving moving images, either monochromatic ("black and white") or color, usually accompanied by sound. "Television" may also refer specifically to a television set, television programming or television transmission. The word is derived from mixed Latin or video Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion image. Noise can block, distort, change or interfere with the meaning of a message in human, animal and electronic communication.

In signal processing Signal processing is an area of electrical engineering, systems engineering, and applied mathematics that deals with operations on or analysis of signals, in either discrete or continuous time to perform useful operations on those signals. Signals of interest can include sound, images, time-varying measurement values and sensor data, for example or computing it can be considered unwanted data The term data refers to groups of information that represent the qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which information and without meaning; that is, data that is not being used to transmit a signal In the public switched telephone network, , in-band signalling is the exchange of signalling (call control) information within the same channel that the telephone call itself is using. An example is DTMF 'Dual-Tone multi-frequency' signalling, which is used on most telephone lines to exchanges, but is simply produced as an unwanted by-product of other activities. "Signal-to-noise ratio" is sometimes used informally to refer to the ratio of useful information to false or irrelevant data in a conversation or exchange, such as off-topic A contribution is on-topic if it is within the bounds of the current discussion and off-topic if not. The terms are normally used in the context of mailing lists, discussion groups, discussion forums, bulletin boards, newsgroups, and wikis posts and spam Spam is the use of electronic messaging systems to send unsolicited bulk messages indiscriminately. While the most widely recognized form of spam is e-mail spam, the term is applied to similar abuses in other media: instant messaging spam, Usenet newsgroup spam, Web search engine spam, spam in blogs, wiki spam, online classified ads spam, mobile in online discussion forums An Internet forum, or message board, is an online discussion site. It originated as the modern equivalent of a traditional bulletin board, and a technological evolution of the dialup bulletin board system. From a technological standpoint, forums or boards are web applications managing user-generated content and other online communities. In information theory Information theory is a branch of applied mathematics and electrical engineering involving the quantification of information. Historically, information theory was developed by Claude E. Shannon to find fundamental limits on signal processing operations such as compressing data and on reliably storing and communicating data. Since its inception it, however, noise is still considered to be information Information, in its most restricted technical sense, is an ordered sequence of symbols. As a concept, however, information has many meanings. Moreover, the concept of information is closely related to notions of constraint, communication, control, form, instruction, knowledge, meaning, mental stimulus, pattern, perception, and representation.^{[citation needed]} In a broader sense, film grain or even advertisements encountered while looking for something else can be considered noise. In biology, noise can describe the variability of a measurement around the mean, for example transcriptional noise describes the variability in gene activity between cells in a population.

In many of these areas, the special case of thermal noise Johnson–Nyquist noise is the electronic noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happens regardless of any applied voltage arises, which sets a fundamental lower limit to what can be measured or signaled and is related to basic physical processes at the molecular level described by well-established thermodynamics In science, thermodynamics is the study of energy conversion between heat and mechanical work, and subsequently the macroscopic variables such as temperature, volume and pressure. The first to give a concise definition of the subject was Scottish physicist William Thomson who in 1854 stated that: considerations, some of which are expressible by simple formulae.

Subjective distinctions

Calling some signal or sound noise is often a subjective distinction. One person's maximum-volume music listening pleasure might be another's unbearable noise.

An annoying background hiss interfering with short-wave radio broadcasts was found to be due to extraterrestrial, indeed cosmic In its most general sense, a cosmos is an orderly or harmonious system. It originates from a Greek term κόσμος meaning "ordered world" and is the antithetical concept of chaos. Today the word is generally used as a synonym of the word Universe . The words cosmetics and cosmetology originate from the same root. In Russian and, processes; listening to this "noise" to the exclusion of all other signals with ever more sensitive antennae An antenna is a transducer designed to transmit or receive electromagnetic waves. In other words, antennas convert electromagnetic waves into electrical currents and vice versa. They are used with waves in the radio part of the electromagnetic spectrum, that is, radio waves, and are a necessary part of all radio equipment. Antennas are used in and receivers is now the science of radio astronomy Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The initial detection of radio waves from an astronomical object was made in the 1930s, but subsequent advances (especially post-World War II) have identified a number of different sources of radio emission. These include stars and galaxies as well as. Radio astronomers are still plagued by noise in their signals—but now it is thermal noise Johnson–Nyquist noise is the electronic noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happens regardless of any applied voltage generated in their equipment interfering with wanted signals from the cosmos.

Acoustic noise

When speaking of noise in relation to sound, what is commonly meant is meaningless sound of greater than usual volume. Thus, a loud activity may be referred to as noisy. However, conversations of other people may be called noise for people not involved in any of them, and noise can be any unwanted sound such as the noise of dogs barking, neighbours playing loud music, road traffic sounds, chainsaws, or aircraft, spoiling the quiet of the countryside.

Acoustic noise can be anything from low-level but annoying to loud and harmful. At one extreme users of public transport Public transport is a shared passenger transportation service which are available for use by the general public, as distinct from modes such as Taxicab, car pooling which are not shared by strangers without private arrangement sometimes complain about the faint and tinny sounds emanating from the headphones or earbuds of somebody listening to a portable audio player A portable audio player is a personal mobile device that allows the user to listen to recorded audio while mobile. Sometimes a distinction is made between a portable player, battery-powered and with one or more small loudspeakers, and a personal player, listened to with earphones; at the other the sound of very loud music, a jet engine A jet engine is a reaction engine that discharges a fast moving jet of fluid to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets and pump-jets. In general, most jet engines are internal combustion engines but non- at close quarters, etc. can cause permanent irreversible hearing damage.

Regulation of acoustic noise

Noise regulation includes statutes or guidelines relating to sound transmission established by national, state or provincial and municipal levels of government. After a watershed passage of the U.S. Noise Control Act of 1972[1], the program was abandoned at the federal level, under President Ronald Reagan, in 1981 and the issue was left to local and state governments. Although the UK and Japan enacted national laws in 1960 and 1967 respectively, these laws were not at all comprehensive or fully enforceable as to address (a) generally rising ambient noise (b) enforceable numerical source limits on aircraft and motor vehicles or (c) comprehensive directives to local government.

Acoustic noise in film sound

For film sound theorists and practitioners at the advent of talkies c.1928/1929, noise was non-speech sound or natural sound and for many of them noise (especially asynchronous use with image) was desired over the evils of dialogue synchronized to moving image. The director and critic René Clair He was born in Paris and grew up in the Les Halles quarter. He attended the Lycée Montaigne and the Lycée Louis-le-Grand. During World War I, he served as an ambulance driver. After the war, he started a career as a journalist under the pseudonym René Desprès. He also made his debut as an actor and became the assistant of Jacques de Baroncelli writing in 1929 makes a clear distinction between film dialogue and film noise and very clearly suggests that noise can have meaning and be interpreted: "...it is possible that an interpretation of noises may have more of a future in it. Sound cartoons, using "real" noises, seem to point to interesting possibilities" ('The Art of Sound' (1929)). Alberto Cavalcanti uses noise as a synonym for natural sound ('Sound in Films' (1939)) and as late as 1960, Siegfried Kracauer was referring to noise as non-speech sound ('Dialogue and Sound' (1960)).

Audio noise

In audio, recording, and broadcast Broadcasting is the distribution of audio and/or video signals which transmit programs to an audience. Receiving parties may include the general public or a relatively large subset of the whole, such as children or young adults systems audio noise refers to the residual low level sound (usually hiss and hum) that is heard in quiet periods of programme.

In audio engineering Audio engineering is a part of audio science dealing with the recording and reproduction of sound through mechanical and electronic means. The field draws on many disciplines, including electrical engineering, acoustics, psychoacoustics, and music. Unlike acoustical engineering, audio engineering does not deal with noise control or acoustical it can also refer to the unwanted residual electronic noise signal that gives rise to acoustic noise heard as "hiss". This signal noise Electronic noise is a random fluctuation in an electrical signal, a characteristic of all electronic circuits. Noise generated by electronic devices varies greatly, as it can be produced by several different effects. Thermal noise and shot noise are inherent to all devices, while other types depend mostly on manufacturing quality and semiconductor is commonly measured using A-weighting A-weighting is the most commonly used of a family of curves defined in the International standard IEC 61672:2003 and various national standards relating to the measurement of sound pressure level .[dubious – discuss] The others are B, C, D and now Z weightings (see below) or ITU-R 468 weighting

Non-acoustic noise

Electronic noise

Electronic noise exists in all circuits and devices as a result of thermal noise, also referred to as Johnson Noise. It is caused by random Randomness is a concept of non-order or non-coherence in a sequence of symbols or steps, such that there is no intelligible pattern or combination. Randomness has somewhat disparate meanings as used in several different fields. It also has common meanings which may have loose connections with some of those more definite meanings. The Oxford variations in current Electric current means, depending on the context, a flow of electric charge or the rate of flow of electric charge (a quantity). This flowing electric charge is typically carried by moving electrons, in a conductor such as wire; in an electrolyte, it is instead carried by ions, and, in a plasma, by both or voltage The voltage between two points is a short name for the electrical force that would drive an electric current between those points. Specifically, voltage is equal to energy per unit charge. In the case of static electric fields, the voltage between two points is equal to the electrical potential difference between those points. In the more general caused by the random movement of charge carriers (usually electrons) carrying the current as they are jolted around by thermal energy. Thermal noise can be reduced by reducing the temperature of the circuit. This phenomenon limits the minimum signal level that any radio receiver A radio receiver is an electronic circuit that receives its input from an antenna, uses electronic filters to separate a wanted radio signal from all other signals picked up by this antenna, amplifies it to a level suitable for further processing, and finally converts through demodulation and decoding the signal into a form usable for the consumer, can usefully respond to, because there will always be a small but significant amount of thermal noise Johnson–Nyquist noise is the electronic noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happens regardless of any applied voltage arising in its input circuits. This is why radio telescopes A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes. In their astronomical role they differ from optical telescopes in that they operate in the radio frequency portion of the electromagnetic spectrum where they, which search for very low levels of signal from space, use front-end Front end and back end are generalized terms that refer to the initial and the end stages of a process. The front end is responsible for collecting input in various forms from the user and processing it to confirm to a specification the back end can use. The front end is an interface between the user and the back end low-noise amplifier The low-noise amplifier is a special type of electronic amplifier or amplifier used in communication systems to amplify very weak signals captured by an antenna. It is often located very close to the antenna, so that losses in the feedline become less critical. This active antenna arrangement is frequently used in microwave systems like GPS, circuits cooled with liquid nitrogen Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4. Liquid nitrogen is often referred to by the abbreviation, LN2 and has the UN.

There are several other sources of noise in electronic circuits such as shot noise Shot noise is a type of electronic noise that occurs when the finite number of particles that carry energy is small enough to give rise to detectable statistical fluctuations in a measurement. It is important in electronics, telecommunications, and fundamental physics, seen in very low-level signals where the finite number of energy-carrying particles becomes significant, or flicker noise Flicker noise is a type of electronic noise with a 1/ƒ, or pink spectrum. It is therefore often referred to as 1/ƒ noise or pink noise, though these terms have wider definitions. It occurs in almost all electronic devices, and results from a variety of effects, such as impurities in a conductive channel, generation and recombination noise in a (1/f noise) in semiconductor devices.

Visual noise

Noise is also present in images. Electronic noise will be present in camera sensors, and the physical size of the grains of film emulsion creates visual noise. This kind of noise is referred to as "grain."

Noise is also used in the creation of 2D and 3D images by computer. Sometimes noise is added to images to hide the sudden transitions inherent in digital representation of color, known as "banding Colour banding is a problem of inaccurate colour presentation in computer graphics. While in 24 bit colour modes, 8 bits per channel should be enough to render images in the full visible spectrum, in some cases there is a risk of producing abrupt changes between shades of the same colour. For instance, displaying natural gradients can show minor". This adding of noise is referred to as "dithering." Sometimes noise is used to create the subject matter itself. Procedural noise (such as Perlin noise) is often used to create natural-looking variation in computer generated images.

Noisy genes

The activity and regulation of our genes are also subject to noise. Transcriptional noise refers to the variability in gene activity between cells in genetically identical populations (even identical twins are non-identical). Noise in gene activity has tremendous consequences on cell behaviour, and must be mitigated or integrated. Noise impacts upon the effectiveness of clinical treatment, with resistance of bacteria to antibiotics In common usage, an antibiotic is a substance or compound that kills bacteria or inhibits their growth. Antibiotics belong to the broader group of antimicrobial compounds, used to treat infections caused by microorganisms, including fungi and protozoa demonstrably caused by non-genetic differences. Variability in gene expression may also contribute to resistance of sub-populations of cancer cells to chemotherapy. In certain contexts, such as the survival of microbes in rapidly changing stressful environments, or several types of scattered differentiation, noise may be essential.

See also

• Noise and vibration on maritime vessels
• Noise music Noise music is a term used to describe varieties of avant-garde music and sound art that may use elements such as cacophony, dissonance, atonality, noise, indeterminacy, and repetition in their realization. Noise music can feature distortion, various types of acoustically or electronically generated noise, randomly produced electronic signals, and
• Noise pollution Noise pollution is displeasing human, animal or machine-created sound that disrupts the activity or balance of human or animal life. The word noise comes from the Latin word nausea meaning seasickness
• Image noise
• Association of Noise Consultants
• Opposite: Silence Silence is the relative or total lack of audible sound. By analogy, the word silence may also refer to any absence of communication, even in media other than speech. Silence is also used as total communication, in reference to non verbal communication and spiritual connection

Additional reading

Kosko, Bart Bart Kosko is a writer and professor of electrical engineering at the University of Southern California (USC). He is notable as a researcher and popularizer of fuzzy logic, neural networks, and noise, and author of several trade books and textbooks on these and related subjects of machine intelligence (2006). Noise. Viking Press. ISBN The International Standard Book Number is a unique numeric commercial book identifier based upon the 9-digit Standard Book Numbering (SBN) code created by Gordon Foster, now Emeritus Professor of Statistics at Trinity College, Dublin, for the booksellers and stationers W.H. Smith and others in 1966 0-670-03495-9.

References

External links

• Guidelines for Community Noise, World Health Organization, 1999
• Audio Measuring Articles - Electronics
• Mohr on Receiver Noise: Characterization, Insights & Surprises
• Noise voltage - Calculation and Measuring of Thermal Noise
• Noise at work European Agency for Safety and Health at Work (EU-OSHA)
• Article "Noise Control Techniques"
• Mountain & Plains ERC: A NIOSH Education and Research Center for Occupational & Environmental Health & Safety
• US National Institute for Occupational Safety and Health, - Noise

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