One result of applying a compressor to an audio signal is that the dynamic range
(difference between the lowest and highest signal levels) is reduced. Another effect is
that you now have control over the dynamics of the signal—thus in a recording situation
you can raise the general perceived level of a signal in the mix without overdriving the
recording medium or monitoring system.
Applications of Compression/Limiting
• Provides “Safe” limits for recording media/broadcast applications:
Compression, since it reduces the overall dynamic range of signals, overcomes the
limitations of recording/reproducing media—for example, compression limits signal
level peaks to within “safe” limits for digital recording. Similarly, in broadcast
applications, compression makes program material fit into the legally-defined maximum
dynamic range of the broadcast signal.
• Effects Limiting:
The limiting aspect of a compressor/limiter also allows the engineer
to set an overall maximum signal level—at a compression ratio of 20:1, any signal level
higher than the threshold setting is effectively clamped to that threshold. The STATUS
Dynamics option is very useful as an effect limiter in these situations.
• Sustain:
A compressor’s ability to reduce variations in signal level can be put to use in
creating sustain effects with instruments—in this example, a guitar. If the compression
ratio is set to, say, 3:1, and the threshold is set to a level well below that of the guitar’s
note, the guitar’s attack and initial sustain is attenuated, but as the note decays, its
level drops off more slowly. (In this example, a 3 dB drop in input signal means only a 1
dB decrease in output signal, until of course the input signal drops below the
threshold.) The perceived effect of the compressor is a sustain effect. Use of the Auto
Make Up or Output Level control can restore the guitar to its original level in the mix.
• Ducking:
Using the Keying capabilities of the compressor/limiter, the engineer can
“duck” one signal under another, such as music under a voice, simply by passing the
first signal (in this case, music) through a compressor, then keying that compressor off
the voice channel. When the talent speaks, compression is applied to the music signal,
creating a “voice-over” effect.
August 1999
B - 3
STATUS 18R
Operation and Maintenance Manual
Appendix B Dynamics Option