Audio equalization can be used to improving the sound of your recordings. Whether using equalization hardware or software at home or in the studio, it’s important to understand the scheme and function of an audio equalizer.
Additionally, it’s important to understand how sound works. When measuring pitch in sound, we count the frequency of sound waves in cycles per second. These are measured in Hertz (Hz). Most people hear sound frequencies between the range of 20 Hz and 20 kHz (20,000Hz). Sound occurrences usually contain multiple frequencies, especially with musical instruments.
In addition to the frequency of a sound wave, the wave’s amplitude can also be measured. This amplitude is the pressure caused by the sound waves, which we perceive as volume and measure in decibels (dB). In audio recording an equalizer can be either ‘hardware’ (analog equipment) or computer software, both are designed to measures the relative change in volume (in decibels) along the frequency spectrum (in Hertz). Since the frequency range is quite wide (20-20,000Hz) it is necessary to group the frequencies in ranges or bandwidths. On home and car stereos, you may find three bandwidths in the equalizer section: bass, middle, and treble. This is one of the most common ways to divide frequencies. Equalization, starting with these broadband divisions can be the best place to begin when using audio equalization.
Low frequencies are generally considered to range from 20Hz to 330Hz, mid frequencies from 330Hz to 4 kHz, and high frequencies from 4 kHz to 20 kHz, but these numbers are relative to the equalizer as well as to the music engineer or producer. When applying audio equalization it is vital to identify the instrumentation and function of instruments in the music and consider the spread of frequency bandwidths. What instrument(s) serve as the bass frequencies? How will the mids be divided, if at all? How dark or bright will each instrument be?
Before you begin to set individual instrument equalizer bandwidths, consider the basics. Up or down. Do you want to accentuate (boost) or attenuate (cut) a certain band of frequency? The more aware you are, the clearer it will be when attempting to attain a given sound through equalization.
One of the simplest ways to adjust equalization is with shelf equalization. In shelf equalization, the adjustment of a certain frequency will include all subsequent lower (for bass) or higher (for treble) frequencies. The image of this EQ looks like a plateau, or a shelf.
Another common type of equalization curve is called peak/dip ‘Bell Curve’ equalization. This means that the decibels in the adjustment can either be accentuated (boosted) or attenuated (cut) at a chosen center frequency. Peak/dip ‘Bell Curve’ equalizers measure the shape of the peak with what’s called ‘Q.’ The higher the Q, the narrower the peak. Generally, Q ranges from 0.7 (covering two octaves in frequency), to 2.8 (covering half an octave), but can be set as low as 0.1 and as high as 100.0, depending on the equalizers design.
A common audio equalization technique is to initially make extreme over-adjustments to hear changes in sound and later to gradually bring these adjustments back, closer to their initial settings. This makes it easier to hear the frequency band in question, but may make it harder to determine how many decibels you want to increase or decrease in the given band of frequency.
Overall, it takes much patience and practice when working audio equalization and there subsequent techniques. Whether you’re using hardware or software equalizers, in your home or studio, you will eventually find equalization types and techniques that suit your work style and compliment you musical productions.