A distortion is the alteration of the original shape (or other characteristic) of an object, image, sound, waveform or other form of information or representation. Distortion is usually unwanted. In some fields, distortion is desirable, such as electric guitar (where distortion is often induced purposely with the amplifier or an electronic effect to achieve the electric guitar's desired, electrifying, aggressive sound). An electric guitar is a type of Guitar that uses pickups to convert the vibration of its steel-cored strings into an electrical current which is made louder An instrument amplifier is an Electronic amplifier that converts the inaudible electric or electronic signal from musical instruments such as an Electric guitar The slight distortion of analog tapes and vacuum tubes is considered pleasing in certain situations. Magnetic tape is a medium for Magnetic recording generally consisting of a thin magnetizable coating on a long and narrow strip of Plastic. This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. The addition of noise or other extraneous signals (hum, interference) is not considered to be distortion, though the effects of distortion are sometimes considered noise. Electronic noise is an unwanted signal characteristic of all electronic circuits. Electric hum, Mains hum, or power line hum is an audible oscillation at the frequency of the Mains Alternating current In Communications and Electronics, especially in Telecommunications, interference is anything which alters modifies or disrupts a signal as

Electronic signals

Graph of a waveform and the distorted versions of the same waveform

In telecommunication and signal processing, a noise-free "system" can be characterised by a transfer function, such that the output y(t) can be written as a function of the input x as

y(t) = F(x(t))

When the transfer function comprises only a perfect gain constant A and perfect delay T

the output is undistorted. Signal processing is the analysis interpretation and manipulation of signals Signals of interest include sound, images, biological signals such as System (from Latin systēma, in turn from Greek systēma is a set of interacting or interdependent Entities, real or abstract A transfer function is a mathematical representation in terms of spatial or temporal frequency of the relation between the input and output of a ( linear time-invariant) In Electronics, gain is a measure of the ability of a circuit (often an Amplifier) to increase the power or Amplitude of a Distortion occurs when the transfer function F is more complicated than this. If F is a linear function, for instance a filter whose gain and/or delay varies with frequency, then the signal will experience linear distortion. Linear distortion will not change the shape of a single sinuosoid, but will usually change the shape of a multi-tone signal.

This diagram shows the behaviour of a signal (made up of a square wave followed by a sine wave) as it is passed through various distorting functions. A square wave is a kind of Non-sinusoidal waveform, most typically encountered in Electronics and Signal processing.

1. The first trace (in black) shows the input. It also shows the output from a non-distorting transfer function (straight line).
2. A high-pass filter (green trace) will distort the shape of a square wave by reducing its low frequency components. A high-pass filter is a filter that passes high frequencies well but attenuates (reduces the amplitude of frequencies lower than the Cutoff frequency This is the cause of the "droop" seen on the top of the pulses. This "pulse distortion" can be very significant when a train of pulses must pass through an AC-coupled (high-pass filtered) amplifier. As the sine wave contains only one frequency, its shape is unaltered.
3. A low-pass filter (blue trace) will round the pulses by removing the high frequency components. A low-pass filter is a filter that passes low- Frequency signals but Attenuates (reduces the Amplitude of signals with frequencies All systems are low pass to some extent. Note that the phase of the sine wave is different for the lowpass and the highpass cases, due to the phase distortion of the filters. The phase of an oscillation or wave is the fraction of a complete cycle corresponding to an offset in the displacement from a specified reference point at time t = 0
4. A slightly non-linear transfer function (purple), this one is gently compressing as may be typical of a tube audio amplifier, will compress the peaks of the sine wave. This article describes the use of the term nonlinearity in mathematics This will cause small amounts of low order harmonics to be generated.
5. A hard-clipping transfer function (red) will generate high order harmonics. Clipping is a form of Waveform distortion that occurs when an Amplifier is overdriven which happens through attempts to increase the voltage or current Parts of the transfer function are flat, which indicates that all information about the input signal has been lost in this region.

The transfer function of an ideal amplifier, with perfect gain and delay, is only an approximation. The true behavior of the system is usually different. Nonlinearities in the transfer function of an active device (such as vacuum tubes, transistors, and operational amplifiers) are a common source of non-linear distortion; in passive components (such as a coaxial cable or optical fiber), linear distortion can be caused by inhomogeneities, reflections, and so on in the propagation path. This article describes the use of the term nonlinearity in mathematics Passivity is a property of engineering systems most commonly used in electronic engineering and control systems This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. In Electronics, a transistor is a Semiconductor device commonly used to amplify or switch electronic signals An operational amplifier, often called an op-amp, is a DC - coupled high- Gain electronic voltage amplifier with differential An electronic component is a basic electronic element usually packaged in a discrete form with two or more connecting leads or metallic pads Coaxial cable is a cable consisting of an inner conductor surrounded by a tubular insulating layer typically made from a flexible material with a high Dielectric constant, all An optical fiber (or fibre) is a Glass or Plastic fiber that carries Light along its length Signal reflection occurs when a signal is transmitted along a transmission medium such as a Copper cable or an Optical fiber, some of the signal power may be reflected Wave propagation is any of the ways in which waves travel through a Waveguide.

Amplitude distortion

Main article: Amplitude distortion

Amplitude distortion is distortion occurring in a system, subsystem, or device when the output amplitude is not a linear function of the input amplitude under specified conditions. Amplitude distortion is Distortion occurring in a System, subsystem or device when the Output amplitude is not a linear function of the Input System (from Latin systēma, in turn from Greek systēma is a set of interacting or interdependent Entities, real or abstract Output is the term denoting either an exit or changes which exit a System and which activate/modify a Process. In Mathematics, the term linear function can refer to either of two different but related concepts Input is the term denoting either an entrance or changes which are inserted into a System and which activate/modify a Process.

Frequency distortion

This form of distortion occurs when different frequencies are amplified by different amounts, mainly caused by combination of active device and components. Passivity is a property of engineering systems most commonly used in electronic engineering and control systems For example, the non-uniform frequency response curve of RC-coupled cascade amplifier is an example of frequency distortion. A cascade amplifier is any amplifier constructed from a series of amplifiers where each amplifier sends its output to the input of the next amplifier in a Daisy chain.

Phase distortion

Main article: Phase distortion

This form of distortion mostly occurs due to the reactive component, such as capacitive reactance or inductor capacitance. In signal processing phase distortion or phase-frequency distortion is Distortion that occurs when (a a filter's Phase response is not linear over the An inductor is a passive electrical component designed to provide Inductance in a circuit Capacitance is a measure of the amount of Electric charge stored (or separated for a given Electric potential. Here, all the components of the input signal are not amplified with the same phase shift, hence causing some parts of the output signal to be out of phase with the rest of the output.

Group delay distortion

Can be found only in dispersive media. In Optics, dispersion is the phenomenon in which the Phase velocity of a wave depends on its frequency In a waveguide, propagation velocity varies with frequency. A waveguide is a structure which guides waves such as Electromagnetic waves Light, or Sound waves Wave propagation is any of the ways in which waves travel through a Waveguide. In a filter, group delay tends to peak near the cut-off frequency, resulting in pulse distortion. In Physics and Electrical engineering, a cutoff frequency, corner frequency, or break frequency is a boundary in a system's Frequency When analog long distance trunks were commonplace, for example in 12 channel carrier, group delay distortion had to be corrected in repeaters. A repeater is an electronic device that receives a signal and Retransmits it at a higher level and/or higher power or onto the other side of an obstruction

Correction of distortion

As the system output is given by y(t) = F(x(t)), then if the inverse function F^-1 can be found, and used intentionally to distort either the input or the output of the system, then the distortion will be corrected.

An example of such correction is where LP/Vinyl recordings or FM audio transmissions are deliberately pre-emphasised by a linear filter, the reproducing system applies an inverse filter to make the overall system undistorted. A vinyl compound is any Organic compound that contains a vinyl group (also called ethenyl) &minus C[[Hydrogen H]] =CH sub>2 See also Frequency modulation, FM band FM broadcasting is a broadcast Technology invented by Edwin Howard Armstrong that A linear filter applies a Linear operator to a time-varying input signal

Correction is not possible if the inverse does not exist, for instance if the transfer function has flat spots (the inverse would map multiple input points to a single output point). A transfer function is a mathematical representation in terms of spatial or temporal frequency of the relation between the input and output of a ( linear time-invariant) This results in a loss of information, which is uncorrectable. Such a situation can occur when an amplifier is overdriven, resulting in clipping or slew rate distortion, when for a moment the output is determined by the characteristics of the amplifier alone, and not by the input signal. In Electronics, the slew rate represents the maximum rate of change of a signal at any point in a circuit

Teletypewriter or modem signaling

In binary signaling such as FSK, distortion is the shifting of the significant instants of the signal pulses from their proper positions relative to the beginning of the start pulse. In Telecommunication, signalling (UK spelling or signaling (US spelling has the following meanings The use of signals for controlling communications In Medicine, a person's pulse is the throbbing of their arteries. The magnitude of the distortion is expressed in percent of an ideal unit pulse length. In Medicine, a person's pulse is the throbbing of their arteries. This is sometimes called 'bias' distortion.

Telegraphic distortion is a similar older problem, distorting the ratio between "mark" and "space" intervals. [1]

Audio distortion

A graph of a waveform and the distorted version of the same waveform

In this context, distortion refers to any kind of deformation of a waveform, compared to an input. Clipping, compression, non-linear behavior of electronic components, modulation, aliasing, and mixing phenomena or power supply inefficiencies can cause distortion. Clipping is a form of Waveform distortion that occurs when an Amplifier is overdriven which happens through attempts to increase the voltage or current Dynamic range compression, also called DRC (often seen in DVD player settings or simply compression, is a process that reduces the Dynamic range of In Telecommunications, modulation is the process of varying a periodic Waveform, i This article applies to signal processing including computer graphics MIX is a hypothetical computer used in Donald Knuth &rsquos monograph The Art of Computer Programming ( TAOCP)

Distorted waveforms

An audio example of a short sample followed by different distorted versions of it.

Problems listening to the file? See media help.

In most fields, distortion is characterized as unwanted change to a signal.

Gabber

Distortion is one of the most important elements of Gabber music. Gabber (IPA pronunciation English /gæbər/ Dutch /xɑbər/ gabba or hardcore, is a style of Electronic music and a subgenre of Distortion filters are usually added on drum patterns and bass lines to achieve a very hard and raw sound.

Main articles: Gabber, Hardcore dance music, Terrorcore, Speedcore, and Hardstyle

Guitar sound

Main article: Distortion (guitar)

Distortion is an important part of an electric guitar's sound in many musical genres, including rock, hard rock, punk rock, garage punk, psychedelic rock and heavy metal. Gabber (IPA pronunciation English /gæbər/ Dutch /xɑbər/ gabba or hardcore, is a style of Electronic music and a subgenre of "Noisecore" redirects here For the style of metalcore see Mathcore. Terrorcore, terror (or in Dutch and French "terreur" is a Music genre. Speedcore is a form of Hardcore techno that is typically identified by its high rate of Beats per minute and aggressive themes Hardstyle, in the United Kingdom sometimes referred to as hardbass, is a genre of electronic dance music that is closely related to hardcore and Hard trance. An electric guitar is a type of Guitar that uses pickups to convert the vibration of its steel-cored strings into an electrical current which is made louder Rock music is a genre of Popular music often though not necessarily employing Electric guitar, Bass guitar, and Drums. Hard rock (also referred to as heavy rock) is a variation of Rock music which has its earliest roots in mid-1960s garage and Psychedelic rock Garage punk is a Rock music Fusion of Garage rock and Punk rock. Psychedelic rock is a style of Rock music that attempts to replicate the mind-altering experiences of hallucinogenic drugs. Typically, the signal coming from the guitar is distorted by a "clipping" of its waveform. This can either be done with an effects pedal that is connected between the guitar and its amplifier or by the amplifier itself working on higher gain-settings in the pre-amplifier. An effects pedal (or a " Stomp Box " is an electronic Effects unit housed in a small metal or plastic chassis used by musicians usually Electric Generally an amplifier or simply amp, is any device that changes usually increases the amplitude of a signal.

Optics

In optics, image distortion is a divergence from rectilinear projection caused by a change in magnification with increasing distance from the optical axis of an optical system. In Photography, a rectilinear lens is a Photographic lens that yields images where straight features such as the walls of buildings appear with straight lines as Magnification is the process of enlarging something only in appearance not in physical size In Optics, the term optical axis is used to define a direction along which there is some degree of Rotational symmetry.

Map projections

Main article: Map projection

In cartography, a distortion is the misrepresentation of the area or shape of a feature. A map projection is any method of representing the Surface of a sphere or other shape on a plane. The Mercator projection, for example, distorts Greenland because of its high latitude, in the sense that its shape and size are not the same as those on a globe. The Mercator projection is a cylindrical map projection presented by the Flemish geographer and cartographer Gerardus Mercator, in 1569 Greenland (Kalaallit Nunaat meaning "Land of the Greenlanders" Grønland is a self-governing Danish Province located between the Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the A globe is a three- Dimensional scale model of Earth ( terrestrial globe) or other spheroid celestial body such as a planet star or moon

See also

• Aliasing
• Amplitude distortion
• Attenuation distortion
• Bias distortion
• Crossover distortion
• Degree of isochronous distortion
• Delay distortion
• Distortion-limited operation
• Distortion (guitar)
• Distortion power factor
• Image warping
• Intermodulation distortion
• Lossy compression
• Overdrive (music)
• Quantization distortion
• Signal-to-noise-and-distortion (SINAD)
• Total harmonic distortion — a measurement of the amount of distortion in a sinusoidal waveform
• Valve sound

References

External links

• A Musical-Distortion Primer
• Guitar Distortion 101
• Multiband Distortion ensemble for Reaktor