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A compressor is basically an automatic volume control. Imagine yourself with your hand on a fader and your eyes on an input level meter. As long as the meter stays below a certain point (the threshold), you leave the fader all the way up and the gain is unchanged. But the instant sound gets louder, you pull down the fader by a certain amount (the ratio). After the sound gets soft again, you push the fader back up. That's what the compressor is doing, except much faster and more accurately than humanly possible.
In mathematic terms: Say your signal is 4db. And yu set your ratio to 2:1. The compressor will take that 4db and turn it into 2db.
Paradoxically, by cutting the peak levels, a compressor allows you to raise the average level of a sound using the Output control to make it sound louder.
Take a vocal signal for instance.
As a singer sings, her voice fluxuates in db level between words and even in the middle of a multi-syllabic word. A singer will say certain syllables lower or higher in volume. By applying a compressor, the lower db syllables are untouched by the compressor but the higher db syllables are lowered. In the whole picture, the lower db syllables seems louder relative to the higher db syllables after it's run through compressor. To the ear, the voice sounds even and controlled.
Compression is often a lot in vocal, bass, and percussions. A lot of engineers like to apply a lot 4:1 to 10:1 ratio on the bass and percussions because that is the foundation of the track.
Last edited by Scottaculous on May-12-2004 at 18:33
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