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Encyclopedia > Graphic equalizer

In audio processing, equalization (EQ) is the process of modifying the frequency envelope of a sound. Etymologically, it means to correct, or make equal, the frequency response of another audio device. The term "equalizer" is sometimes applied to audio filters in general, though strictly speaking not all audio filters are equalizers. Audio signal processing, sometimes referred to as audio processing, is the processing of a representation of auditory signals, or sound. ... A schematic representation of auditory signaling Sound is an alternation in pressure, particle displacement, or particle velocity propagated in an elastic material (Olson 1957) or series of mechanical compressions and rarefactions or longitudinal waves that successively propagate through medium that are at least a little compressible (solid, liquid or gas... Etymology is the study of the origins of words. ... An audio filter is a type of filter used for processing sound signals. ...


Overview

There are a number of kinds of EQ. Each has a different pattern of attenuation or boost. A peaking equaliser raises or lowers a range of frequencies around a central point in a bell shape. A peaking equalizer with controls to adjust the level (Gain), bandwidth (Q) and center frequency is called a parametric equalizer. If there is no control for the bandwidth (it is fixed by the designer) then it is called a quasi-parametric or semi-parametric equalizer. Electronics In electronics, gain is usually taken to meaning the ratio of the signal output of a system to the signal input of the system. ... Analog Bandwidth is the width, usually measured in hertz, of a frequency band f2 − f1. ... The Q factor or quality factor is a measure of the quality of a resonant system. ... The center frequency f0 (resonant frequency) is the geometric mean between the lower cutoff frequency f1 and the upper cutoff frequency f2 of a frequency band. ...


Shelving type equalizers increase or attenuate the level of a wide range of frequencies by a fixed amount. A "low shelf" will affect low frequencies up to certain point and then above that point will have little effect. A high shelf affects the level of high frequencies, while below a certain point, the low frequencies are unaffected.


One common type of equalizer is a graphic equalizer, which consists of a bank of band-pass filters, with an independent gain control for each band. Normally, these bands are tight enough to give at least 3dB or 6dB maximum effect for neighboring bands, and cover the range from around 20Hz to 20kHz (which is approximately the range of human hearing). A simple equalizer might have bands at 20Hz, 200Hz, 2kHz and 20kHz, and might be referred to as a 4-band equalizer. A typical equalizer for live microphone work might have as many as 24 or 32 bands. The frequency axis of this symbolic diagram would be logarithmically scaled. ...


Uses

Early telephone systems used equalization to correct for the reduced level of high frequencies in long cables. For example, a particular microphone might be more sensitive to low frequency sounds than to high frequency sounds, so an equalizer would be used to increase the volume of the higher frequencies (boost), and reduce the volume of the low frequency sounds (cut). A telephone handset A touch-tone telephone dial Telephone This article is about telephone technology. ... A microphone with a cord A microphone, sometimes called a mic (pronounced mike), is a device that converts sound into an electrical signal. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ...


One of the most direct uses of equalization is at a live event, where there are microphones and speakers operating simultaneously. An equalizer is used to ensure that there are no frequency bands where there is a round trip gain of greater than 1, as these are heard as audible feedback. Those frequencies are cut at the equalizer to prevent this. Closeup of a loudspeaker driver A loudspeaker is a device which converts an electrical signal into sound. ... In cybernetics and control theory, feedback is a process whereby some proportion or in general, function, of the output signal of a system is passed (fed back) to the input. ...


In practice, there is a degree of aesthetics involved, in addition to technical considerations. Aesthetics (or esthetics) (from the Greek word αισθητική meaning a perceiver or sensitive) is a branch of philosophy dealing with the nature of beauty. ...


See also


  Results from FactBites:
 
Equalization - Wikipedia, the free encyclopedia (808 words)
The term "equalizer" is eroneous applied as a general term for audio filters.
One common type of equalizer is the graphic equalizer, which consists of a bank of sliders for boosting and cutting different bands (or frequencies ranges) of sound.
An equalizer is used to ensure that there are no frequency bands where there is a round trip gain of greater than 1, as these are heard as audible feedback.
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