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3.1 Compression/Leveling/Limiting/Clipping
After describing the the individual sections in detail, we would now like to acquaint you with further important
concepts pertaining to the processing of dynamics:
Compression
A compressor reduces a broad dynamic range to a limited dynamic band. The resulting dynamic range
depends on the threshold, attack, release and ratio settings. As the desirable effects of a compressor include
the boosting of low-level signals, the threshold value is generally set low. Inaudible compression requires
fast attack and release times and low compression rates. Faster attack and release times and higher com-
pression rates increase the effect on short-term dynamics. This may be put to use to achieve audible,
creative sound effects, for example.
Leveling
The leveling function is used to keep the output level constant, i.e. to compensate for long-term changes in the
input level without restricting short-term dynamics. The threshold is generally set low to ensure that low-level
signals will be boosted. The leveling function uses slow attack and release times in conjunction with a high
ratio. Due to its very long attack times, leveling does not affect signal peaks or short-term changes of the
average level.
Limiting
The limiting function uses short attack times, a high compression ratio and a release time which depends on
the given application and the desired audio effect. The threshold must be set high, as a limiter is only used to
set a ceiling for high signal levels. The degree of dynamic range reduction depends on the ratio setting and
the extent to which the threshold is exceeded. A so-called program limiter uses attack times greater than 20
ms and is designed to control the average level. Short-term signal peaks exceeding the set threshold value can
also pass the limiter in this case. Peak limiters use attack times set to less than 5 ms to control signal peaks
as well.
Clipping
Unlike the two previous limiter types, the clipping function is characterized by the use of instantaneous attack
and release, as well as infinite compression rates to ensure absolute limiting for all signals above the set
threshold (brickwall limiting). Clipping has the effect of a radical cutoff of signal peaks exceeding the
threshold without restricting the amplitude of the actual signal form. Under normal circumstances, the clipping
function is inaudible and may even result in improved audio quality under certain circumstances by cutting off
artificial harmonics. Clipping causes conspicuous, harsh distortion, which at its most extreme can result in
rectangular waveforms.
3.2 The Gate section
The main task of a Gate is to separate undesirable background noise from the program signal and "remove" it
inaudibly. As described in Chapter 4.1.4, a so-called Downward Expander automatically reduces the overall
level for all signals below a user-definable threshold and thus increases the dynamic range of the program
material. The Expander can thus be regarded as the opposite of a compressor/limiter. Expanders generally
work with a relatively flat ratio characteristic to ensure that the signal is continuously suppressed. On the other
hand, noise gates can be regarded as high-ratio expanders, which radically cut signals off that drop below the
threshold.
The BEHRINGER ULTRA-DYNE PRO is equipped with six Noise Gates with intelligent look-ahead functions.
The Threshold parameters can be set up individually for each band using faders in the EDIT menu of the
PROCESS mode. Additional parameters such as the Hold and Release times and look-ahead can be found on
setup level 2 in the band menus. The following definitions describe the parameters in greater detail:
Gate Threshold:
This is the value after which the audio signal no longer passes through the Gate.
Gate Hold Time:
The Gate Hold time is the duration of the wait after the Threshold has been passed before the release time
3. APPLICATIONS