Now comes the time that we need to address actual characteristics of different frequencies, as well as the different octaves that humans can hear. (As in, how many are there actually?)

As always, let’s follow the flow of logic. The simple question first:

How many octaves are there in the human hearing range of 20-20kHz?

The answer is 10.

If we take the lowest frequency humans can hear, which by now you know is 20Hz, and then simply double that number until we reach the 20k range, we’ll end up with 10 total octaves encompassing the 20-20kHz range.

Here is the exact break down:

20 Hz | Octave 1 40 Hz | Octave 2 80 Hz | Octave 3 160 Hz | Octave 4 320 Hz | Octave 5 640 Hz | Octave 6 1280 Hz | Octave 7 2560 Hz | Octave 8 5120 Hz | Octave 9 10240 Hz | Octave 10 20480 Hz

Now, here is a little side note: I’m sure you have all heard the terms “1 octave”, “1/3 octave”, or even “2/3 octave” EQs.

Let’s keep it simple and not over-think it. Those are just more subdivisions between octaves to get more accurate or surgical tone shaping from an equalizer. I’m sure all of you at some point have worked with equalizer units of some sort, so I won’t muddy everything up here by detouring into an EQ tutorial; suffice to say, everything that happens, no matter how small the subdivision, is all between 20Hz-20kHz. Those 10 octaves are our focus.

Continuing with our overarching theme of frequency training, I would be grossly negligent if I didn’t give you the basic “characteristics” or “tonal qualities” of our 10 octaves. This is where you must recall the homework assignment in which you had to document the sonic qualities heard in your own “shorthand”. If you didn’t do it before, please take 10 minutes to go back and do it now – it’s important!

Now then, time to compare notes:

Characteristic Sounds: Bands 1-5

I’ll preface this by saying that although there are countless sounds and tones in our world; they all do share similar qualities. Let’s hone in on some of those!

We’ll focus on the lowest 5 octaves for now and the latter 5 for the next article in the series.

Octave 1 (20-40Hz)

This is your sub low region. Notes here are felt more than actually heard. VERY high end speakers will reproduce this range…but it will still be largely inaudible!

Octave 2 (40-80Hz)

Now this is where you audible musical low end is found. This is where you EQ a kick drum for more oomph. Same for a bass guitar. BUT….be careful! Too much, and you risk turning things into a rumbling mess, AND you are wasting all that energy which will cost you overall volume!

FYI: This is one of the first places we (mastering engineers) trim back to balance your mix and get more overall volume. Excessive low end requires tremendous power.

It’s very easy to get carried away in this frequency area. Let’s face it….it feels great when you can, well, feel the music!

Octave 3 (80-160Hz)

We are still in the bass range here. (More “upper bass” actually) I really like this area, since you can dial in a lively punchy bassy sound, AND avoid the dreaded excessive low end rumble.

Hint: GREAT place to lock bass guitar and kick drum together. Also wonderful for distorted low tuned guitars.

Octave 4 (160-320Hz)

This range has many un-flattering names which I won’t utter here. It is a transitory octave, and sadly highly misunderstood. This is the crossroads between upper bass and low midrange. Too much boost in this area and you have sludge filled, murky, and wooly sounds. Too little, and your music sounds thin and lifeless.

This region is also a common meeting ground for a lot of musical instruments’ fundamental or dominant frequencies. Look back at all the past articles’ examples…

That last sentence is why this octave is so misunderstood and misused. Consider this octave a “tie-in” point for your whole mix of instruments!

Note: I have purposely avoided discussing pitch ranges for instruments, since I want you to really focus on the sound here regardless of the sound source. The only exception is with Octave 4, for the reason mentioned above.

Octave 5 (320-640Hz)

We are in low midrange land here. If Octave 4 is the common “meeting ground” for musical instruments’ fundamental or dominant frequencies, then this midrange octave is where all of those voices fight for dominion.

The midrange octaves (5 and 6) are THE MOST IMPORTANT frequency range.

Read that sentence again.

This octave (and octave 6 to be discussed in the next article) is where you decide the dominant instrument or vocal that will project forth ahead of the others. At the same time, more subtle fine-tuning, gives the rest of the instruments a loud and clear voice. Consider this to be the “projection” octave(s).

Why?

Simple answer: This is the most sensitive range we can hear.

There is an old mastering adage:

Get the midrange right and everything else will fall into place.

Once you understand that almost all sounds we hear are prominent when featured in the midrange band, then the above statement makes sense. It took me years to learn that!

Once again, the midrange can be misunderstood – and misused as well. Too much, and you end up with “boxiness”. Too little, and you’re thinning out the herd again. You end up with all bass, high mids and treble, but no real volume or authority. Tread carefully here!

Homework

This will be a simple assignment. We will use some of the same sounds we used before in order to maintain constant “control” subjects. The familiar sounds we will use are:

Kick Drum

Snare Drum

Floor Tom

For EQ boosts I will use common starting points that most EQs feature:

31Hz …..for Octave 1

…..for Octave 1 62Hz …..for Octave 2

…..for Octave 2 125Hz …for Octave 3

…for Octave 3 250Hz …for Octave 4

…for Octave 4 500Hz…for Octave 5

Tech note: I will use excessive boosting (WAY more than “proper” EQing) for the sole purpose of making those sonic characteristics stand out!

Practice Tracks

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

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!) 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! 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”.

That’s it for now! Simple homework right?

Conceptually, and on the surface, yes!

But consider this: How good a chef would one be if he/she didn’t know the taste of salt; or sugar; or cinnamon; or, actually, any of the basic culinary ingredients? How well could that chef prepare even the simplest of dishes?

See my point?

In our next article we’ll be looking at the top 5 octave bands in a similar way. For now, focus on these low and midrange octaves!

Bonus Question

Here’s a reminder of the mystery bonus question at the end of the last article:

Q: How do you go about finding which frequency to EQ, when trying to fix a problem?

(It doesn’t matter what the issue is; boominess, shrill, thin, too boxy sounding, etc.)

Hint: This method will also double up as a great way to locate a dominant frequency!

The answer is called “frequency sweeping”.

It involves the use of a parametric equalizer. (If you don’t know what a parametric equalizer is, there’s a great introduction over at AudioTuts+)

Here are the steps:

Play the audio clip in question through EQ bypassed or set flat.

(Just to establish a baseline.) Reduce the overall output of signal at the EQ output stage by about 1/3

(you’ll see why in a second!) Now pick just one band of the EQ and turn the gain of that band ALL the way up.

(Naturally that will cause a huge volume boost….hence the pre-emptive strike of step 2) Set the bandwidth control to the mid point.

Bandwidth determines how far of an influence the frequency and gain control have on the adjacent and tangential frequencies. A wider bandwidth has more of an overarching influence, where as a really narrow bandwidth is razor sharp and focused only on the frequency selected. Since we are on an exploratory mission, I say a good half way point is the right compromise. Play the audio clip and slowly start to sweep through the whole frequency range, from 20Hz all the way up to 20kHz.

As you slowly do this, eventually you will hit the frequency that resonates (“mirrors”) with the frequency you are having an issue with. Once you get to that point, stop. Check the frequency, and write it down. Reset the EQ to flat, set the volume back up to normal. Play the audio again, only this time, dial in the frequency you located in step 5, and slowly reduce the gain of that frequency.

The amount of reduction necessary will vary, but you’ll adjust accordingly until the problem spot is tamed down.

Notice, when you are performing step 5, that the frequency that resonates with the “problem” frequency will usually increase in volume drastically. Congratulations! As a bonus point, you have just located a dominant frequency of your sound source. Now, keep in mind it might not always be the main, or fundamental frequency, but it will still get you in the ball park.

Grant you, this is a cumbersome way to find a frequency, especially when there are easier ways to locate frequencies (e.g. spectrum analyzers); but if you are in a position where you don’t have the luxury of analysis tools, believe me, this will save the day. And you WILL find yourself in less than ideal situations in which you will have to perform a little creative engineering…

And now for this week’s bonus mystery question:

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

I’m purposely leaving this one broad and open ended!

Hint: The answer has to do with “resonance.”

Answer next time!

Until then….

Any problems or questions leave a comment or come join us in the Forums!

Test yourself:

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

