[sdiy] VERY cool/bizarre: Buchla noise

[harrybissell]

Gene... those are excellent ways of putting it.  I'm being picky to explain
WHY the MM5837 sucks (for a synthesizer noise source) although as a
source for (let's say) a room equalizing instrument it is actually VERY good.

In the first case... it is obviously NOT truly random...
in the second case.. it might as well be truly random

well said !

H^) harry

Gene Stopp wrote:

> OK philosphy students... this is a good one frankly. Whenever I try to
> explain PRBS stuff to people (usually customers, usually in regards to
> internet traffic data patterns or framesize distributions) I end up using
> phrases like "it's not really random but it's pretty darn close" and
> "subjectively random" and "it might as well be truly random" and "but it
> will repeat after a while" and "it's generated by a digital machine so it's
> not truly random" etc. etc. Looks like the definition of "random" is what's
> in question here.
>
> If you keep adding bits to the shift register length you will quickly reach
> a point at which the repeat interval (assuming you put the feedback taps in
> the right place) is far beyond a single human lifespan. If we can all agree
> that that is random, then the cutoff point between psuedo-random and random
> is somewhere in between.
>
> Although it's certainly out there past 17 bits :)
>
> - Gene
>
> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Harry Bissell Jr
> Sent: Wednesday, September 29, 2004 3:12 PM
> To: Rainer Buchty; Metrophage
> Cc: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] VERY cool/bizarre: Buchla noise
>
> I still don't agree... It is NOT truly random
> as it does not have an infinite number of states...
> it has only as many as the length of the register.
>
> Think of a register with four bits... the
> lowest frequency it can generate would be
> 1111000011110000  etc...
> the highest is
> 1010101010101010
>
> The all ones (or zeros depending on the logic) state
> will latch the device and it must be avoided or
> recovered from.
>
> It approaches 'random' and over the short term
> (compared to other methods) is a good way to generate
> noise - as long as you don't recognise that it
> IS NOT RANDOM !!!
>
> (but it is good enough for rock 'n roll :^)
>
> H^) harry
>
> --- Rainer Buchty <rainer at buchty.net> wrote:
>
> > >I think you've nailed it right there! It is not
> > random.
> >
> > *No* PRNG (i.e. noise generated by a feed-back shift
> > register) is true
> > random but shows a periodic behavior. That's why you
> > should use at least
> > 22, 23 Bits so that pattern repeat takes place in
> > the domain of a few
> > minutes rather than seconds.
> >
> > Rainer
> >
> >