Apple Soundtrack Pro 2 - Manual (Page 339)

Chapter 11 Working with Audio Effects 339
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:
 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.
 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.
 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.
 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.
 High-frequency and low-frequency reverb time: These parameters let you specify the
decay of higher and lower frequencies separately. Different surfaces, such as wood
floors and concrete walls, absorb high and low frequencies at different rates, and
these parameters let you simulate the sound of different environments more closely.
 Reverb envelope: Lets you control how much the volume of the reverb changes over
time. In natural acoustic situations, the reverb echoes decay gradually over time. You
can re-create this gradual decay, or gate the reverb so that it cuts off more abruptly.
Meters and Diagnostic Effects
Diagnostic effects help you analyze and clean up audio in a variety of ways. Each type
of diagnostic effect provides a different way to “look at” an audio clip or file, and each
has a unique set of parameters. These effects are available only as realtime effects in
the Effects tab and the Mixer, not as processing effects.
Correlation Meter
The Correlation meter displays the phase relationship of a stereo signal. A correlation of
+1 (plus one, the far right position) means that the left and right channels “correlate”
100% (that is, they are completely in phase). A correlation of 0 (zero, the center position)
indicates the widest permissible left/right divergence, often audible as an extremely
wide stereo effect. Correlation values less than zero indicate that out-of-phase material is
present, which can lead to phase cancellations if the stereo signal is combined into a
monaural signal.