Apple Soundtrack Pro User Manual download pdf (Page 198)

198 Chapter 9 Working With Audio Effects

Limiters

Limiters (also called peak limiters) prevent the audio signal from exceeding a maximum

volume level. A compressor gradually attenuates levels above the threshold, but a

limiter puts a hard limit on any signal louder than the threshold. You use a limiter

mainly to prevent clipping.

Noise Gates

A noise gate alters the signal in the opposite direction from a compressor. While a

compressor lowers the volume of sounds above the threshold, a noise gate lowers the

sounds below the threshold. Loud signals pass through unchanged, but softer signals,

such as the decay of a loud instrument, are cut off. Noise gates can be used to

eliminate low-level noise or hum from an audio signal.

Distortion Effects

Distortion effects simulate the sound of analog and digital distortion. After working to

eliminate the digital distortion caused by clipping from a project, why would you add

distortion as an effect? The distortion produced by overdriven vacuum tubes (which

were used in amplifiers and music recording equipment before the development of

digital recording technology) produces an effect which many people find pleasing, and

which is integral to many styles of popular music. Analog tube distortion adds a

distinctive warmth and bite to the signal.

There are also distortion effects which intentionally cause clipping and digital

distortion of the signal. These can be used to modify vocal, music, and other tracks to

produce an intense, unnatural effect, or for creating sound effects.

Distortion effects include parameters for tone, which let you shape the way in which

the distortion alters the signal, and for gain, which let you control how much the

distortion increases the output level of the signal.

EQ and Filter Effects

EQ is likely the most common audio effect used in postproduction. You can use EQ to

shape the sound of a project by adjusting specific frequencies or frequency ranges.

Using EQ, you can create both subtle and extreme changes to the sound of your

projects.

Most EQ effects make use of filters. As the name suggests, a filter allows certain

frequencies to “pass through” to the output while stopping or attenuating other

frequencies. EQ effects include highpass, lowpass, and band pass filters.

When the audio signal passes through an EQ filter, the frequencies that pass through

can be raised or lowered in volume. Raising and lowering frequencies using EQ is often

referred to as boosting and cutting frequencies. You can create many changes to the

sound of your project by boosting and cutting various frequencies.

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Apple Soundtrack Pro User Manual Page 198