Forums > MaxMSP

bounded chaos in msp

April 29, 2009 | 8:31 pm

i’m looking for a way to create a chaotic signal (as in audio rate), preferably with a power spectrum varies on time-scales of the order 1 second.

I use chaos in the technical sense of the logistic map, etc. In order to be practical, the signal should be bounded, making the logistic map a good candidate.

I tried implementing a logistic map (next = a*prev*(1-prev) for a between ~3 and 4) with tapin/out but couldn’t figure out how to inject exactly one vector of noise into the feedback loop. I’m not sure that this would have the sound i’m after, anyway.

I tried messing around with it, I added a tanh~ to enforce the -1, 1 bound and a highpass filter to block fixed points, which is interesting, but tends toward limit cycles very quickly (or noise). Adding a second delay of different length increased the decay time significantly, but it still basically goes to a limit cycle.

suggestions?


April 30, 2009 | 10:32 am

André Sier’s A-Chaos lib is the obvious place to look.

There are also a few chaotic signal generators in Litter Power. You can grab the free Starter Pack to take a look, although for your purposes the more interesting objects are probably in the Pro Bundle.

You’ll find a few other objects at maxobjects.com.


April 30, 2009 | 3:02 pm

i’ll take a look at those.

but more generally, is there a way to simulate differential equations in the signal domain inside max?


April 30, 2009 | 3:45 pm

i found this paper: http://www.elec.qmul.ac.uk/dafx03/proceedings/pdfs/dafx11.pdf

which decsribes an fexpr~ object which would be ideal for my purposes. if only i could get my hands on it. maybe yadegari would lend me the source code.


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