compander.help.lhs

compander input control thresh slopeBelow slopeAbove clampTime relaxTime

Compressor, expander, limiter, gate, ducker.  General purpose dynamics
processor.

input: The signal to be compressed / expanded / gated.

control: The signal whose amplitude determines the gain applied to the
         input signal. Often the same as in (for standard gating or
         compression) but should be different for ducking.

thresh: Control signal amplitude threshold, which determines the break
        point between slopeBelow and slopeAbove. Usually 0..1. The
        control signal amplitude is calculated using RMS.

slopeBelow: Slope of the amplitude curve below the threshold. If this
            slope > 1.0, the amplitude will drop off more quickly the
            softer the control signal gets when the control signal is
            close to 0 amplitude, the output should be exactly zero --
            hence, noise gating. Values < 1.0 are possible, but it
            means that a very low-level control signal will cause the
            input signal to be amplified, which would raise the noise
            floor.

slopeAbove: Same thing, but above the threshold. Values < 1.0 achieve
            compression (louder signals are attenuated) > 1.0, you get
            expansion (louder signals are made even louder). For 3:1
            compression, you would use a value of 1/3 here.

clampTime: The amount of time it takes for the amplitude adjustment to
           kick in fully. This is usually pretty small, not much more
           than 10 milliseconds (the default value).

relaxTime: The amount of time for the amplitude adjustment to be
           released. Usually a bit longer than clampTime if both times
           are too short, you can get some (possibly unwanted)
           artifacts.

Example signal to process.

> import Sound.SC3

> let { e = decay2 (impulse AR 8 0 * lfSaw KR 0.3 0 * 0.3) 0.001 0.3
>     ; p = mix (pulse AR (mce [80, 81]) 0.3) }
> in audition (out 0 (e * p))

Noise gate

> let { e = decay2 (impulse AR 8 0 * lfSaw KR 0.3 0 * 0.3) 0.001 0.3
>     ; p = mix (pulse AR (mce [80, 81]) 0.3)
>     ; z = e * p
>     ; x = mouseX KR 0.01 1 Linear 0.1 }
> in audition (out 0 (mce [z, compander z z x 10 1 0.01 0.01]))

Compressor

> let { e = decay2 (impulse AR 8 0 * lfSaw KR 0.3 0 * 0.3) 0.001 0.3
>     ; p = mix (pulse AR (mce [80, 81]) 0.3)
>     ; z = e * p
>     ; x = mouseX KR 0.01 1 Linear 0.1 }
> in audition (out 0 (mce [z, compander z z x 1 0.5 0.01 0.01]))

Limiter

> let { e = decay2 (impulse AR 8 0 * lfSaw KR 0.3 0 * 0.3) 0.001 0.3
>     ; p = mix (pulse AR (mce [80, 81]) 0.3)
>     ; z = e * p
>     ; x = mouseX KR 0.01 1 Linear 0.1 }
> in audition (out 0 (mce [z, compander z z x 1 0.1 0.01 0.01]))

Sustainer

> let { e = decay2 (impulse AR 8 0 * lfSaw KR 0.3 0 * 0.3) 0.001 0.3
>     ; p = mix (pulse AR (mce [80, 81]) 0.3)
>     ; z = e * p
>     ; x = mouseX KR 0.01 1 Linear 0.1 }
> in audition (out 0 (mce [z, compander z z x 0.1 1.0 0.01 0.01]))