Frequency Fundamentals

We now continue our discussion of the 10 audible octaves. We left off at Octave 5 in Part 1. Onward….

Characteristic Sounds: Bands 6-10

Octave 6 (640-1280Hz)

This is midrange land again. Remember Octave 5, and now 6 are referred to as the projection octaves.

Specifically, here in Octave 6 rests the difference between a focused and loud projection, and laser beams of searing sound with a highly “nasal” quality. The same rules that apply to Octave 5 apply here as well.

A final note: this is also the beginning of higher, or upper harmonics. (The next article will have a breakdown of harmonics)

Octave 7 (1280-2560Hz)

Here we are in the upper midrange region. Consider this the region that amplifies everything that came before it. This is the region that can add volume to a nicely dialed low- to mid-midrange, or give articulation to a vocal. Guitars can come alive here as well. This is where you make things intense or even a little harder.

BUT…..beware those same qualities overused will give you harshness, and ear fatigue from too much focus and volume. This is where that hard SHHHHHHHHH sound lives. (Good old fashioned high/mid sibilance.) Remember the hi-hat trash can sound we discussed? Well, the first part of that spectrum lives right here!

Octave 8 (2560-5120Hz)

This area is the treble or presence region. (Technically, you could also call it “lower treble”; and Octave 9 that follows “higher treble”). I happen to like this break down a little better, since it avoids the semantic confusion. For instance, here, we refer to the “presence” of a sound as taken to mean the clarity of the sound, whereas guitar players refer to the “presence” control on their amps as the extreme treble response which is above and beyond the “normal” treble.

So, to avoid confusion, let us;
a) Refer to “lower” and “upper” treble (Octave 8 being lower)
b) Substitute “articulation”, “detail” and other similar words to describe presence.

Alright; crucial points for this frequency range. Vocal clarity and detail live here. Conversely, too much and the extra brightness causes ear fatigue rather quickly. The ear is rather sensitive to higher frequencies, and since the formula is “the higher the Hz, the less power required to amplify those frequencies” you can quickly see how abuse can have a stringent sound. Treble sibilance happens here also. (Read about the sibilance that happens at octaves 7 and 9, and picture this in-between region. Annoying SHHHHH and sssss’sss live here with excessive boost.)

But, again, conservative use and you are talking about the “definition” and “clarity” of sound! All instruments and sounds can benefit here.

Word to the wise: Always learn the full frequency response of each sound or instrument that you want to EQ, as certain sounds have no business being messed with in certain octaves.

I’ll give a VERY obvious example. If you are tweaking a distorted guitar, you have very little to EQ past the 5-7k range. Why? Because, the round warm distorted sound all guitar players and listeners alike enjoy starts to steeply roll of at around 7k. Anything above that and you are boosting harmonics and frequencies that contribute to the “can of bees” sound. (The sound you get by amplifying a distorted electric guitar through a full range system…YUK…I know that YOU know what I’m talking about!)

On the other hand, a clear bass guitar can be EQ’d well into the 10-16k range, with the harmonics amplified providing a nice, clear, crystalline sound. Perfect for that!

There I go again; I didn’t mean to turn this into a mixing and EQ tutorial, but it seemed relevant to point out the power of the treble regions!


Octave 9 (5120-10240Hz)

This is now the high treble region. Take everything described above for Octave 8 and apply it here. The only difference being this: the boosts will be “thinner”, “sharper”, and more “piercing”. Here is where you detail the detail. I know that sounds absurd… but this is where the “brilliance” of cymbals, synths, metallic percussion, and string sounds happen.

Over-exert this region and you are into ultra-high sibilance. (This is the region where certain people overemphasize the sss’s…you know the sound. In vocal recording, this can be a nightmare. (Fortunately there are de-essers and sibilance control devices, but again, that is beyond the scope of our mission here!)

Octave 10 (10240-20480Hz)

This is the region often referred to as the “air” or “openness” of sound. It’s one of those regions where it is felt more than heard. Now don’t take that last sentence as gospel because indeed, when over-boosted this is the region where “hiss” and other noise artifacts love to lay their claim!

To end Octave 10 on a positive note; keep in mind that a slight and gentle boost in this area can provide just the right amount of “life” to the sound. It’s that…“can’t quite place it” clarity and “air” that can make or break a recording!

(“Air” really is just about the perfect descriptive term for this area. Audio professionals can sometimes be like cats and dogs, rarely agreeing on anything, and even debating certain things for decades; but this is one place where we ALL agree on the term “air”!)


An overall final note: We have learned by now that the lower frequencies’ wave travels slower and therefore require the most power to reproduce. Following that train of thought; as the frequencies get higher and therefore have faster waves, the amount of power required to reproduce them goes down!

Simply put, the higher the frequency, the less power required when amplifying it.

On that note, here is some golden advice:

A well-balanced mix should gradually roll off the amplitude of the frequencies as they get higher and higher. On a spectral analyzer (which we’ll talk about in part 5), the overall wave should be a steady decline, with most of the peaks and prominent information being in….you guessed it: The midrange area, followed by the low end response.


The “assignment” here, is a continuation of Part 3’s assignment. Same steps – just the latter 5 octaves! Here are our “control” subjects.

The familiar sounds we will use are:

  • Hi-Hat
  • Cymbal Combo (3 crashes and 3 positions of ride)
  • Tom 1 (High Tom)

Remember: Since we are EXCESSIVELY boosting everything, naturally all characteristics will come through with way too much “spice”… but you WILL hear that spice clearly!

For EQ boosts I will use latter 5 common starting points that most EQ’s feature:

  • 1000Hz… for Octave 6
  • 2000Hz… for Octave 7
  • 4000Hz… for Octave 8
  • 8000Hz… for Octave 9
  • 16000Hz… for Octave 10


Practice Tracks

↓ Boost / Track → High Tom Hi-Hat Cymbal Combo
Original (No EQ)
1 (1kHz)
2 (2kHz)
3 (4kHz)
4 (8kHz)
5 (16kHz)

Remember: You can save these to your computer or MP3 player to practice any time. For the graphical player, press ‘Download’ while the clip’s playing. For the plain links, just right-click and “Save As…”

Steps for you – same exact steps as in Part 1:

  1. Listen to each sample “flat” – the original, un-EQed version.
    This is to refresh and establish an anchor point.
    (I trust you are starting to see the importance of reference or anchor points!)
  2. Now listen to each sample at each of the five octaves discussed.
    There are 5 versions of each samples, each EQd specifically to highlight the characteristics of the 5 octaves discussed. Characteristics and sound manipulations are literally endless; but as usual, we build on the main ones… Anchor points, Anchor points, Anchor points!
  3. Listen, listen and listen again!
    The lesson objective is to familiarize you with each characteristic discussed. That’s it! Don’t over think it. Just listen and listen. By repetition and rote you will start to become familiar with these sonic “flavors”.

Bonus Question

Remember our mystery question from the last article?

What is special or unusual about the floor tom sound samples?

The special or unusual quality that the floor tom possesses is this:

The 5 octaves that were EQ’d with their respective frequencies (31, 62, 125, 250, and 500Hz) were all the same frequencies that are the make up of the floor tom.

The floor toms’ dominant frequency is 62Hz. It also has lower and higher harmonics (second, third, fourth, etc. frequencies) which are all the same as the 5 EQ bands used. That caused resonance at those given points, which caused the volume to rise quite above the other sounds demonstrated! Consider that all the other sounds used anywhere from 12-18dB boost on the EQ bands, while the floor tom used roughly half of that to achieve the same perceived volume.

Now the EQ frequency sweeping technique should come to focus! For example, as soon as I boosted 62Hz on the floor tom… WOW… It just exploded. 62Hz boost on top of the 62Hz originally there. Exponential rise in volume! (Same with the other 4 frequencies – to different degrees of course!)

Hint: To EQ the floor tom in a real mix, I would suggest adjustment at other frequencies not directly in correlation with the dominant, 2nd, 3rd, 4th, etc. frequencies; OR, if you absolutely want to adjust at those particular ones, then keep in mind you will have to cut the EQ gain up to 50% to avoid ridiculously excessive volume boosts.
That principle holds true for ANY sound and EQ process!

Now….. This week’s mystery bonus question:

What is EQ feathering?


A word on the next article – We are finally at the point where we will tie this 6 part series together. Here we will finally discuss compound frequencies and harmonics, as alluded to in previous installments. We will also look at some real life EQ, and frequency play when we combine sound sources. Once again, I am not trying to turn this specifically into a mixing tutorial, but we will use some mixing examples to show how frequencies fight for dominion – and ultimately, what you can do to create sonic balance!

Until then…

Test yourself:

You might also like to try Quiz 1: Percussion Frequencies or the Drum Kit Quiz!

We have a forum dedicated to Audio EQ, mixing, mastering, and frequency training topics – Come join the discussion!

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