## audacity-nyquist

 Re: [Audacity-nyquist] sigma function + "amplitude would be compressed, but nothing happens to frequency or ambience." From: Igor Chernenko - 2008-12-02 23:03:11 Attachments: Paul's sigma function.png     Paul's sigma function modified k 3.png ```Hi Paul, I do not know exactly, but it seems that the only amplitude is transformed. Otherwise, one should not, perhaps, apply such a compression. And if it is really true, you can try many interesting nonlinear functions. Your "sigma function" seems to be a very good idea. I will try it. But it should be modified. You see, your function S = Exp(t) / (1 + Exp(t)) > 0 It is always positive! This means that the amplitude of the compressed wave will be always positive too. As you know: -1 <= sin(x) <= 1 -1 <= cos(x) <= 1 Your function can be modified in this way: S_modified = -1 + 2*(Exp(x) / (1 + Exp(x))) I am going to try this one: S = -1 + (2*exp(k*x))/(exp(k*x)+1) It should be "normalized", of course. Many thanks for interesting idea! It is obvious that the quality of the compressed sound depends on the compression function. Therefore, many different functions should be tried. Best regards, Igor P.S. The plots are in the attachment QUOTE from the Nyquist documentation: (s-exp sound) A generalized exponential function. If sound is a SOUND, compute e^(x) for each sample x. If sound is a number x, just compute e^(x). If sound is a multichannel sound, return a multichannel sound with s-exp applied to each element. The result has the type, sample rate, starting time, etc. of sound. (s-log sound) A generalized natural log function. If sound is a SOUND, compute ln(x) for each sample x. If sound is a number x, just compute ln(x). If sound is a multichannel sound, return a multichannel sound with s-log applied to each element. The result has the type, sample rate, starting time, etc. of sound. Note that the ln of 0 is undefined (some implementations return negative infinity), so use this function with care. http://www.cs.cmu.edu/~rbd/doc/nyquist/part8.html ```
 [Audacity-nyquist] Web page for Igor's Tanh From: paul beach - 2008-12-07 15:19:31 ```Hi All, There is a web for Igor's Tanh Plug-in here, http://www.climatehoax.ca/audio/ I was asked about the symbol sound that I used as a demo. This is a sound font, I think the file extension is .sf2 You can google Sound Font cymbal, I think this is a method that is considered horrible; but a lot of people just use it anyway. The web page was done in two days and will be under revision for quite some time. -- paul beach sniffyraven@... ```