Understanding frequency is a basis of using the EQ more effectively whilst mixing. Knowing how the frequencies in your mix fill the frequency spectrum and knowing when to cut and boost then is a skill to develop if you want to be a better engineer.
Technically, frequency is the rate of which your sound signal repeats within a cycle of positive and negative amplitude, which is measured in Hertz (Hz). If you go into your DAW and zoom into one of your audio file, you will notice this repeated cycle.
As the rate of repeated cycle increase, so does the frequency. For instance, higher frequencies will have more repeated cycle in a second than a do lower frequencies. So a 200Hz signal has 200 cycles in a second, while a 1000Hz signal has 1000 cycles per second.
As you can see, the wavelength of a low frequency signal is longer than that of a high frequency signal making high frequency signals more directional than is low frequency signals. This means you can place your subwoofer anywhere in your room because you will still hear the full force of the sound emitting from it. On the other hand, to get the full effect of the sound emitting from your tweeter, it must be pointing right at you.
Understanding Frequency relation to musical notations
Since all musical notes all related to sound, they all have a fundamental frequency. Take the most commonly used example, the A above the middle C on the piano, which is 440Hz. But musical notes not only produce a fundamental frequency but also harmonic frequencies.
If you pluck the open low E string on an acoustic guitar, it will vibrate at the fundamental frequency of 82.4Hz, but it will also vibrate at the second harmonic frequency of 164.8Hz, which is an octave above. It will also vibrate at the third harmonic of 329.6Hz, the fourth harmonic of 659.2 Hz and continues infinitely.
Without the harmonic frequencies, every instrument would sound the same. The harmonic frequencies give each instrument their unique sound.
Since every instrument has various notes with their own fundamental frequency, therein its own harmonic frequencies, each instrument will occupy a particular range of frequencies.
If all the instruments in your mix occupying a particular frequency range, it will make your mix sound over crowded and muddy, making mixing more difficult. You need to EQ so that each instruments occupied its own frequency range across the whole frequency spectrum.
In the Mixing
According to the doctrine of hearing, we can only perceive frequencies of 20Hz to 20kHz, which is debateable but I won’t get into that in this post. To make things less complicated in mixing, this frequency range is divided into four ranges: low frequencies, low mid frequencies, upper mid frequencies and high frequencies.
This ranges from 20Hz-250Hz. This is where you will find your sub, bass and your low frequency instruments. 20Hz-30Hz are frequencies that are often filtered out when mixing, because we cannot hear much in this range, especially through small speakers, and information with these frequencies often show up in your mix as rumble.
30Hz- 250Hz is where you will find the fundamentals of the bass and the kick. The lower end of this range is much more ‘boomy’ but the right amount will make your mix sound thicker. The higher end of this range is much more punchy but too much will make your mix sound muddy.
This ranges from 250Hz-1kHz. 250Hz can add warmth to the mix, but too much will make it ‘woofy’ and muddy sounding. The fundamentals of a male vocal, the snare and the toms are around this point.
Frequencies ranging from 750Hz to 1kHz can sometimes add presence to some instrument but too much will make the mix sound boxy and if you have too many instrument around this range in the mix, you will lose clarity.
This ranges from 1kHz-9kHz and you are getting in the zone where you can had presence to vocals, but excessive boost in this area will cause listening fatigue.
The right amount of boost around 1kHz-2kHz can add some upper mid range presence to the mix. Boosting area between 4kHz and 6kHz will make your vocal more clear and defined, making it pop/stand out in the mix. Frequency around 6kHz-9kHz will make the mix more ‘edgy’.
This ranges from 10kHz -16kHz or to 18kHz. The reason why I say 16kHz – 18kHz and not 20kHz, is because most of us cannot hear frequencies above 16kHz, due the wearing of our ears over the course of our lives. Any boost in this area will add brightness and clarity, but too much will produce artefacts such as sibilance.
To get better at EQing, you not only need to know when the frequencies are located but also you need to know what cutting and boosting these frequencies does to your audio and a good way to get better at this is by learning to hear these frequencies and know then by heart.
There are various tools out there that can help to develop your ability to hear frequencies; here is one I would recommend. By developing an understanding and perception of common frequencies through practice, applying EQ will become much more easier.
And remember, if you found this post helpful or you think there is something I could have added, leave a comment below and let me know. 🙂
Read my most popular post, what you need to setup a home recording studio.
Image by: Visually Intense Productions