# compression ratio in compressor function:

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Khaled Abdellatif on 23 Apr 2019
Commented: khaled hassan on 20 May 2019
hallo all,
Is there a way that one could interpret the compression ratio in the compressor.
it value varies from 1 to 50,
From the MATLAB page: the compression ratio is defined as R=(x[n]−T)(y[n]−T).
But: in the example:
drc = compressor(-15,5);
visualize(drc);
%How can we recaluculate (to know) what was the compression ratio from the graph?
Is the compreesion ratio (standard) the slope i.e the dofference between Inputs/Outputs??
can one give an example?
thanks a lot

Charlie DeVane on 24 Apr 2019
Hi Khaled,
Looking at the static characteristic (input/output graph), the ratio R is the reciprocal of the slope above the threshold. (Below the threshold the slope is 1.) In the doc example, above threshold the output increases 3 dB for a 15 dB increase in input, so the slope is 3/15 = 0.2. The ratio is the reciprocal of that: 15/3 = 5.
In the doc for compressor you can find the equation for the static characteristic above threshold, where you can see that the slope is 1/R:
hth,
Charlie
khaled hassan on 20 May 2019
Thanks Charlie!!
do you know if there is a way to have several knee points: thresholds for one compresso rin MATLAB?
best wishes,
Khaled

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