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Prevalent in professional recording studios, a graphic equalizer is an audio device that allows the user to see and control different sound frequencies. Equalizers allow a user to manually adjust the bass, treble and bandwidth for almost any type of audio to ensure the sound quality is full, robust and properly balanced. Sometimes, an audio equalizer is used to adjust for background noise or inconsistent audio levels. They are frequently used to sharpen the sound quality and reduce echoes or microphone feedback in music recordings, public address systems and sound systems for live performances. The use of an equalizer can often make a very noticeable difference in overall sound quality. A graphic equalizer does all the things a regular equalizer does but it also represents the frequency controls visually.
Typically, a graphic equalizer is designed with a bank of individual knobs or sliders which slide up and down the control panel independent of the other sliders. Each knob alters the frequency ranges of the audio that the equalizer is set up to control. Usually, the knobs are configured in a way that forms a graphical curve — the "graphic" in graphic equalizer refers to this very visual illustration of how the audio is set to be controlled. In other words, it displays a measurement of how uniformly the range of high and low frequencies are represented. Some equalizers are also equipped with a built in digital display that creates a graphical representation of the changing sound frequencies as they occur.
There are different types and varying degrees of graphic equalizers. While a simple consumer radio might only provide a bank of filters which control two or three channels for stereo sound adjustment, a professional-style equalizer generally encompasses 25 to 31 bands or more. These are often referred to as one-third octave equalizers because the center frequency of each filter is spaced one third of an octave apart, allowing for three filters per octave.
Also known as a graphic EQ, a graphic equalizer can be found on a high-end consumer stereo as well as a computer. Some are constructed with the familiar slider design while others are made with dial-like knobs. In the traditional slider design, the buttons corresponding to the lowest frequency levels of a sound recording are generally to the left side of the device while the higher frequencies are to the right side. Setting the equalization is a simple matter of beginning at center frequency where all of the controls are set at a neutral position. As the listener analyzes the audio material, the sound frequencies can be adjusted either greatly or minutely by merely sliding the buttons up to increase gain or down to reduce gain.