Thanks for your two recent plugs - unfortunately my Windows comp is still
in repairs so I haven't been able to play with Audacity for a while.
Have you thought of posting to the Audacity users group, which is a _much_
larger group of people than on this list. That's what I do when I'm
Linkname: Audacity-users Info Page
David R. Sky
On Sun, 23 Nov 2008, Igor Chernenko wrote:
> Nonlinear Compressor/Limiter/Expander - Nyquist plugin for Audacity
> File: "Nonlinear-Compressor XI.ny" (in the attachment)
> Nonlinear compression can produce natural loudness, simply
> because it is more natural than linear compression.
> If you do not like any loudness, try to decompress sound with
> expander (compression degree < 0).
> For compressing speech, try these presets:
> Threshold = 0.66; compression degree = 1; compression power = 3
> If it is too strong, take compression power = 1
> and/or a higher threshold.
> The Nonlinear Compressor might be a good substitute for Leveller.
> It works well for iRiver E100 recordings. This depends, of course,
> on how recordings were made.
> HOW IT WORKS
> Nonlinear Compressor performs smooth non-linear transformation of the sound
> rather than classic compression.
> Afterwards, the sound is amplified to the previous level. If compression
> degree < 0, it works as expander.
> Although compression curves look similar to those of classic compressor, the
> non-linear curves are
> smooth, and this makes the difference.
> The magic formula of compression is this one:
> Y = X - beta*(((1-alpha)/3)*X^3 + (alpha/11)*X^11)
> alpha >= 0
> beta <= 1
> X = sound
> Y = compressed sound
> Threshold = (2/33)(4*alpha+11)
> alpha = (1/8)*(33*Threshold-22)
> This "esoteric formula", of course, is a Taylor polynomial of the 11th
> order. Do not worry!
> The 11th order is not a problem anymore, for we have a magic computer
> algebra system
> called Maxima. It is easy to use, and it is free, open source and
> cross-platform. You can
> train sophisticated math, solve equations, and build graphics on Linux and
> Windows for free.
> Maxima homepage:
> To understand how the Nonlinear Compressor works, you may need to see
> compression curves.
> Such curves can be easily produced with Maxima. I use "wxMaxima" together
> with "gnuplot"
> on Ubuntu Linux. This "wxMaxima" is so designed that you do not need to read
> documentation (or help-file) on Maxima. I have not read yet.
> It would be much more convenient, of course, if the Nonlinear Compressor
> would also display
> graphics of compression curves. But Nyquist does not support such things.
> One may need
> Python, and the source code of Audacity, and this might be a long story...