This article will focus on a such thing as equalization and such device as equalizer.
The history of an equalization began with the first movies that has a terrible sound of the character’s voices. Then sound producers decided to use the frequency selection effect to improve the sound as part of the the post production stage.
In time, an equalization also had become applicable in music sphere and had been a big part in the sound engeneering by advances in radio technology.
An equalization is a selectional process of the signal’s aplitude changing that is based on the frequency responce of the signal (tone, pitch).
There are two types of such electronic devices as equalizer. It is a parametric equalizer and a graphic equalizer.
A parametric equalizer principle of working is pretty simple.
In the most popular submission you have three basic ranges of frequency (low, middle, high). And you can choose to amplify signal, to attenuate or not change the amplitude of the signal in the determined range of the frequencies. A attenuate of the amplitude is carried out by spinning the knob counterclockwise (-dB) . Respectively, an aplification
is carried out by spinning the knob clockwise (+dB).
Graphic equalizer is a set of sliders, each of which is responsible to amplify or attenuate an amplitude of the electric signal in a certain frequency. You can see it in picture on top.
Sources
https://en.wikipedia.org/wiki/Equalization_(audio)
https://ru.wikipedia.org/wiki/%D0%AD%D0%BA%D0%B2%D0%B0%D0%BB%D0%B0%D0%B9%D0%B7%D0%B5%D1%80
Radio technology in music 