Apple Soundtrack Pro User Manual download pdf (Page 203)

Chapter 9 Working With Audio Effects 203

Delay effects let you set the delay time, the time between the original signal and the

delayed signal. Delays often provide parameters for feedback (also called regeneration),

which let you set how much of the delayed signal is fed back into the delay’s input,

creating more repetitions of the delay (like the number of “bounces” in an echo).

Specific types of delay have other parameters: Tap tempo delays let you set the delay

time by physically tapping a key or controller; stereo delays include parameters for the

pan position of the output signal, which can be shifted over time using a low-

frequency oscillator (called an LFO).

Reverb

Reverberation, usually shortened to reverb, simulates the sound of acoustic

environments such as rooms, concert halls, caverns, or the sound of infinite space. In

any acoustic space, sounds echo off the surfaces of the space (the floor, walls, and

ceiling) over and over, gradually dying out until they become inaudible. Reverb effects

consist of thousands of delays, of varying lengths and intensities, that simulate these

natural echoes. Reverb helps define the sense of space in which sounds take place, and

can be used to simulate both realistic and fantastic acoustic environments.

The first form of reverb actually used a room with hard surfaces (called an echo

chamber) to add echoes to the signal. Mechanical devices, including plates and springs,

were also used to add reverberation to the output of instruments and microphones.

Digital sound recording has made it possible to use digital reverbs, which use complex

algorithms (sets of equations) to simulate various acoustic environments with greater

accuracy and flexibility.

Simple reverb effects provide parameters for the decay time or reverb time, which let

you set how long the reverb lasts before dying away, and the mix or level, which you

use to set the ratio of the effected signal (called the wet signal) to the original (the dry

signal). More sophisticated reverbs can include the following parameters:

Â Room type: Lets you set the type of space the reverb will simulate: a small or large

room, a hall, or another type of acoustic space.

Â Predelay time: In an acoustic space, there is a short period of silence between a

sound and the time when the initial echoes of the reverb begin. Different spaces

have different amounts of predelay, which helps “tell” our ears how large the space is.

Longer predelay settings also help separate the original (dry) signal from the effected

(wet) signal, making it sound clearer and sometimes larger.

Â Early reflections: The first echoes to arrive from the surrounding surfaces in a space

are determined by the size and shape of the space, and “tell” our ears what type of

space it is.

Â Diffusion: Lets you set the number of the echoes in the reverb. Hall reverbs typically

have low diffusion settings, while plate reverbs typically have high diffusion settings.

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Apple Soundtrack Pro User Manual Page 203