Changing the frequency response of a given audio signal by adjusting the amplitude of the signal usually in an effort to achieve a flatter frequency response (although often misused to alter the audio signal to a more “pleasing” form which is a distortion of the intended signal – for instance, artificially adding bass for a more visceral impact). Equalizing a signal simply means changing it at certain frequencies. For instance, music played back over a particular sound system may drop in sound level at 4 kHz due to room interactions. The frequency response of the system could be “equalized” by giving signals a boost at 4 kHz (adjusting the amplitude of the signal at 4 kHz by increasing it). If the boost matches the drop present without equalization, the frequency response will be flattened resulting in a more realistic response that more closely reproduces the intended signal. hink of a field with a trench running through it. If you fill in the trench you have equalized the field or changed its form. By filling in the trench you get a nice, level field that is more useful. The same is true if you have a ridge running through the field. If you flatten out the ridge, the field is flat and more useful. Sound equalization works in a similar manner filling in the trenches and cutting down the ridges in the frequency response. hen properly used and set up, equalization can often improve the sound of a given audio system, however, equalization should be used only after an audio system is properly set-up and other efforts at creating a more realistic frequency response have failed to yield the desired results. Equalizers may add some noise to a system and can be used improperly to alter sound away from its intended reproduction, thus their proper use is required.