having the object at full sample rate frequency and then adjusting the bias to a low value, just so a few of the samples are of an inverse polarity, also creates a nice texture!

Done!

Now for the big question, where are the Reverb algorithms based on velvet noise?

here's the code, object should be in the next release any time now, just need Tim to help me compile a few things... https://github.com/porres/pd-else/blob/master/Code_source/Compiled/audio/velvet~.c

thanks again

So here's the fixed version: velvet-noise-fixed.pd

It wasn't just the issue with small floating point numbers, but more importantly it now didn't work with integer periods. In this case, of course, the period must never be reduced by one sample!