A band equalizer is a tool which is designed to change the output of sound by making adjustments within various bands set by the operator of the equalizer. Equalizers are used during recording to get sound of a clear, crisp quality and they are also utilized during production to further clean up recordings and get the best possible sound. In live performance, a band equalizer can be part of the sound system which is used to control quality.
With a band equalizer, the goal is not to make sweeping changes to all of the sound, but to make changes within specific bands on the audio spectrum with the use of a band pass filter. This allows people to filter out very specific types of sounds without involving the signal as a whole. For example, a sound engineer working on recording a performing orchestra could use a band equalizer to isolate the sounds of different instruments, filter out sounds like feedback, shuffling feet, and other unwanted noises, and return a clear audio signal.
The operator of the band equalizer can make a number of adjustments to achieve desired sound goals. Sound engineers are very well versed in the types of sounds they work with and how they behave during recording or performance. In the example above, for example, the sound engineer knows about the frequency range of each instrument in the orchestra, so that the engineer can make sure that actual orchestral sounds are not accidentally cut out while the recording is made and processed.
Equalizer or EQ levels are determined at the start and may be adjusted as needed during recording and performance. This is done with the use of a sound board, a large piece of equipment which allows for very precise manipulation of recordings and live performance. Often a sound board represents options visually so that the sound engineer can imagine a map of the audio spectrum mapped on the board and make adjustments accordingly.
Learning to use an audio equalizer requires training and a good ear. Training gives people the technical skills they need to understand how and why to use equalizer equipment, while the good ear ensures that a sound engineer can hear the results of the work. Using a band equalizer allows a very high degree of isolation and control when working on equalization with a complex audio signal, so that the engineer can keep desired sounds and discard undesirable ones.
