6–12 dB: Drastic adjustment
0–6 dB: Typical adjustment
50–100 Hz: (Bass range) Increase for bass “boom”; decrease to help clarity
200 Hz: (Low musical range) Increase to add fullness; decrease to reduce muddiness
400–880 Hz: (Vocal range) Increase for clarity; decrease to enhance presence
1.5kHz–7kHz: (Overtones) Increase for punch and presence; decrease if sound is thin
10+ kHz: (Overtones) Increase for brightness; decrease to reduce hiss/ess
Dynamics processors modify the amplitude range of sound, from quieting
noises you want to deemphasize to “squeezing” the overall range so tracks
can sound louder to adjusting certain loudness levels of sounds. You could
keep one hand on the fader at all times and manually adjust dynamics, but
dynamics processors are capable of performing efficient, automatic edits
that produce effects your fingers can’t.
Compressors take the overall dynamic range and compress it to a smaller range
by reducing the amplitude of a signal when it rises above a certain thresh-
old. Counterintuitively, you’ll typically apply compression to make your
track sound louder. After bringing the loudest peaks of a sound down within
100 1k 10k
Figure 7.21 To create an EQ
curve with the sound you
want, you’ll need to listen to
your sound in different ranges
of the spectrum. Here are
some approximate ideas of
how much to boost or cut,
and in what ranges. Different
instruments will vary, so once
you have a sense of the basic
ranges, your ear will be your
best tool.
7: P
a more manageable range using a compressor, you can safely turn up the
entire track’s volume, which will bring out sounds that otherwise might be
too soft to hear easily. The behavior of a compressor is controlled by a
number of parameters:
Threshold (dB): The threshold is the amplitude level beyond which
the compressor begins to reduce the level of the signal: when signal
amplitude exceeds this value, the compressor becomes active.
Ratio (input:output): Ratio determines the amount of gain reduction
that will be applied when the input passes the threshold; it’s a ratio of
the input gain to the output gain. If the ratio is set to 3:1, a 3 dB
increase in input gain beyond the threshold results in just a 1 dB
increase in the output. Some compressors also include a knee setting,
which adjusts the curvature of the point where reduction begins; not
surprisingly, this point looks like a “knee” (Figure 7.22).
Attack/release (ms): In order to reduce the output level as the input
level rises past the threshold, compressors act like an automated volume
fader. Attack and release timings determine how quickly or slowly the
compressor makes its gain adjustments. Attack is the amount of time
during which the reduction begins to take effect, and release (some-
times called decay) is the amount of time during which the compres-
sion goes away, returning the output level of the signal to the same level
as the input level. Imagine you are watching a mixer: whenever a signal
crosses the meter beyond a certain number of decibels (the threshold),
you reach for the fader and pull it down more or less quickly (the
attack); when the signal crosses back below the threshold, you return
the fader to its original level (release). Typically, you’ll want to strike a
balance between settings that are too short (creating an audible pump-
ing sound, though that can be useful for a special musical effect, as
mentioned in the following tip) and settings that are too long (which
can sound artificial).
Output gain (dB): Output gain (more descriptively called “make-up
gain”) simply adds volume to the sound after it’s been processed by the
compressor. Compression makes the overall sound softer, since it’s
reducing the gain of the signal whenever the signal rises past the
threshold. By adding output gain, you can restore the overall average
amplitude of the sound, amplifying softer sounds in the process.
What a compressor
Reduces overall
dynamic range by mak-
ing louder sounds quieter
How to use it:
Set a
threshold above which
the signal will be reduced,
an amount of reduction,
and the timing charac-
teristics (attack and
release times), then set
the output gain to make
the overall sound louder
When to use it:
smoothing out” the
dynamic range of a track,
you can use compres-
sion to make sound
denser and louder by
increasing output gain.
Compression is often
applied to instruments
like drums, guitar, and
Milliseconds (ms):
Short periods of time
are usually indicated in
audio software using
the term milliseconds
(abbreviated ms). A
millisecond is 1/1000
of a second; there are
1000 ms in a single
second.You’ll often
see envelope attack
and release times and
the delay time in delay
effects indicated in ms.

Get Real World Digital Audio now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.