Equalization

Equalization (or equalisation, EQ) is the process of changing the frequency envelope of a sound in audio processing. In passing through any channel, an audio signal will "spread" from its original qualities. The goal of equalization is to correct, or make equal, the frequency response of a signal.

The term "equalizer" is often incorrectly applied to audio filters, such as those included on DJ mixing equipment and hi-fi audio components. However, these "equalizers" are typically general all-purpose audio filters, which can be arranged to produce the effect of low pass, high pass, band pass and band stop filters. Such filters are true equalizers only when arranged to reverse the effects of internal circuitry on sound output.