Recording - September 2013 - 8

Note to faithful writers: When sending your letters by email,
please remember to include your name and where you hail from.
A question we get with surprising frequency
Wow, where have you been all my life? I stumbled
across your website when looking up how to mix low
end, and I think your instructional videos are the best
I’ve seen. Very simple, to the point, none of that complex
jargon that only a professional engineer would understand. Wow! I like it! You are now my go-to magazine
and website.
I have a small home recording studio, with all the
basics, an Alesis USB mixer, Pro Tools, and all these little
nick-nacks in between. I have been recording my stuff for
7 years and I still don’t always understand what I’m
doing. Thank God for www.recordingmag.com.
I do have one suggestion for a video. I have never really
understood the concept of frequencies, such as “boosting at
such and such Hz or kHz”, “800 Hz vs 2–4 kHz”, “below
100 Hz”, etc. I read these everywhere, but don’t really
understand it in layman’s terms. I’m a visual person—
reading is one thing, seeing is another. I would like to better understand this in a visual format if that’s feasible?
Again—Thank you for being out there. The industry
is changing dramatically. Signed, a new subscriber,
Carl S. Simons
via email

Hello Carl, thanks for the kind words. I’m glad the
videos work for you.
In our August 2013 issue, Eric Ferguson in his
Recording Fundamentals column began a look at frequencies and how to adjust them with equalizers; his
treatment continues this month. But on a more basic
level, let me provide some simple facts.
The air vibrations that your ears perceive as sound
can happen at very different speeds, and how many
vibrations happen per second is expressed in Hertz
(abbreviated Hz). One Hz is one vibration per second.
The number of vibrations per second is the frequency.
Now, 20 Hz is usually listed as the lowest frequency (the slowest rate of vibration) we can hear, but
good luck finding a speaker that actually reproduces
20 Hz cleanly. If you find one and lightly touch the
diaphragm, you can practically feel the rhythm of
the vibrations of those low notes.
Then again, a newborn with perfect hearing is
assumed to perceive pitches as high as 20,000 Hz
(usually expressed as 20 kHz, where k is kilo =
1,000). Good luck hearing that, too. Most of us are
lucky to truly really fully hear 10 kHz as adults.
The note of A above middle C, the A that is used for
tuning forks etc., is at 440 Hz. At every higher octave
the number of Hz is double, at every lower octave the
number of Hz is half. So the A above that tuning-fork
A is 880 Hz, and the one below it is 220 Hz.

You can see that the distance from 10 kHz to 20 kHz
is only an octave in musical terms, and no instrument
produces notes as high as 10 kHz, let alone 20 kHz.
The highest key on an 88-key piano is about 4.2 kHz.
Now the fun part (discussed in more detail by Eric)
is this: Most every sound, except some simple test
tones, is composed of many frequencies, not just one.
The lowest in such a “stack” is called the “fundamental” (usually the pitch of the note you play), the
others are called “overtones”.
If you only had the fundamental, you couldn’t
make much interesting music with it; it would sound
as lame and neutral as a sine wave. Even a sine wave
is rarely heard pure, because most speakers through
which you hear one (from a synth or a test instrument) already have some distortion.
What happens is this: The fundamental is augmented by higher frequencies, a bit like in a chord,
except that those higher ones are much softer than
the fundamental. If they were as loud as the fundamental, you’d hear a chord... a pure musical one if all
the overtones had a harmonic relationship to the
fundamental, or a very dissonant noise-like “chord”
if the overtones were not in a harmonic relationship
to the fundamental and to one another.
When you use equalization, you adjust the volume
of these overtones that give the overall sound its
tonal characteristic. Say you have a bass note of A
three octaves below middle C, which is 55 Hz (the
“fundamental” in this case), and you mess with a frequency band of 220 to 440 Hz, you’re adjusting the
overtones from roughly A below middle C to A above
middle C. Boost that range and the bass gets more in
your face, attenuate that range and the bass gets
mellower.
Just remember the doubling and halving as you go
up and down the range of pitches, and remember
tuning A = 440 Hz, and you can always get a rough
idea of where you are in a spectrum. If you adjust a
frequency band of 100–200 Hz for a flute track (the
lowest possible note a flute can produce is middle C,
about 262 Hz), don’t expect anything to happen...
Experiment! Record yourself speaking at a normal
pitch, then use eq in varying frequency bands, and
you’ll soon hear which band makes what difference.
Then do the same thing with musical examples, and
soon you’ll develop a memory for what works roughly, and with time you’ll zero in on problems more
exactly, by ear and from experience.
I’m sure you get it, and when you’ll read Eric’s articles and see his illustrations, it will all become even
more clear. Happy Recording! Cheers—LzR

Write to us at: Talkback, Recording Magazine, 5408 Idylwild Trail, Boulder, CO 80301
Or save stamps and send email to talkback@recordingmag.com
8

RECORDING September 2013

http://www.recordingmag.com

Recording - September 2013

Table of Contents for the Digital Edition of Recording - September 2013