Real World Digital Audio

 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

D

YNAMICS

P

R OCESSOR S

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.

Compressor

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

12

6

–6

–12

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.

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C

HAPTER

7: P

ROCESSING AND

E

FFECTS

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.

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D

YNAMICS

P

ROCESSORS

What a compressor

does:

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:

By

“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

vocals.

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.