How to EQ – What Are Frequencies?

How To EQ

What Are Frequencies?

​By Lij Shaw -

Ok so you just got started in Garageband or Protools even and you have all these killer new plugins at your disposal that you have never seen before. They look so awesome and seem so powerful!

So why does your head hurt when you start trying to figure out how to use all these amazing plugins? 

Lets start with the simplest tool and probably the most useful next to the level fader,

EQ = The Equalizer.

Despite the fact that it sounds like you will be endowed with super hero powers, here is what Wikipedia says about EQ:

The Oracle Wikipedia

Equalizers are used in recording studios, broadcast studios, and live sound reinforcement to correct the response of microphones, instrument pick-ups, loudspeakers, and hall acoustics.[2] ... ...Equalizers are also used in music production to adjust the timbre of individual instruments by adjusting their frequency content and to fit individual instruments within the overall frequency spectrum of the mix.[3]:73–74

Oops! That may not have helped that much. Now you’re even more confused!

So let’s dig in deeper. Most likely all you care about is how is this thing going to make my song sound killer when I mix it? Right? And thats a good question…

So Lets start at the bottom and work our way to the top.

First of all what is EQ?

  • In the simplest form EQ or equalization is a way to filter your audio to boost or cut certain frequencies with the intent usually of making your recordings sound better.
  • It may be that the microphone didn’t capture what you wanted when recording and you need to correct it.
  • Or it may be that you just want to change the overall sound of a track. Perhaps you want to give it an old timey filter for example…
  • EQ is a tool that you can use to change the sound and create something new.

Frequencies are the waveforms that make up sound. Sound is a wave of particles moving through the air just like a wave moving across the surface of the water. However a water wave is on a flat plane (sort of) while a sound wave is expanding out in three dimensions like a sphere.

If the waves are big with a long space between peaks then they are low frequencies, meaning that the frequency of waves is not that many per second.


Frequency Differences

If the waves are happening quickly then they create high frequencies. Low frequencies create sound like bass and subs in music while high frequencies create sounds like treble and "air".

Frequency is measured as the number of peak to peak wave forms happening every second.

So one Hertz is one wave per second. The Frequencies that we care about in sound are from the lowest 20 Hertz (or 20 Hz) to the highest audible frequency 20 KiloHertz or (20 KHz). This is the extent of what the human ear can hear (not including anyone with exceptional hearing).

Most of us can’t even hear the full range from 20-20k. You can test yourself to find out what you hear.

Frequencies in music can be described as octaves. An octave is a doubling of the frequency. So the first musical frequency that we can hear (or feel) is the C note, “C0″, that’s at 16.35Hz which is just below the lowest frequency we can hear at 20 Hz. Then the octaves double as they go up and you find middle "C" at 261.63 Hz four octaves up from the bottom. the highest octave on a piano is "C8" at 4186.01 Hz or almost 4.2 kHz. And finally the top of human hearing is about "C10" which is at 16744.04Hz or about 16.7kHz. This is ten octaves above the lowest note "C0".

( I referenced some of this from Easy Ear Training if you want to read more. )  

The bottom octave of hearing is 20 Hz to 40 Hz. While the top Octave of audio is a much larger range of frequencies from 10KHz to 20 KHz. Notice that the first octave is only a difference in frequency of 20 wave forms per second while the top octave is a difference of 10 thousand wave forms per second!

(There is a lot LESS room in music for a variety of low notes to be present than the vast amount of space available for higher frequencies. But that’s another discussion)

If you want to get more practice understanding EQ then I highly recommend a cool little app called Quiztones. This app lets you practice identifying various tones and EQ selections.

Good luck!

And please add your comments below: What did you find helpful about this post? What do you think I missed that is important to you?


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