[sdiy] VERY cool/bizarre: Buchla noise

[Harry Bissell Jr]

For the most part... an analog noise source
with its warts and all (poor spectral distribution,
popcorn noise etc...) is truly random.  It does not
repeat.  Or say that knowing the past behavior is not
any predictor of the next state.

PRNG is NOT random... but it is random enough for
my attention span (about an hour). You might say it
approaches randomness.

H^) harry



--- mark verbos <mverbos at earthlink.net> wrote:


---------------------------------
    thing is, in that case it NEVER repeats. And in
the case of random,repeats DO happen. So, to me, it
seems like a long shift registersequence is more
varied than random even. no?

Mark



Gene Stopp wrote:  
OK philosphy students... this is a good one frankly.
Whenever I try toexplain PRBS stuff to people (usually
customers, usually in regards tointernet traffic data
patterns or framesize distributions) I end up
usingphrases 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 itwill repeat
after a while" and "it's generated by a digital
machine so it'snot truly random" etc. etc. Looks like
the definition of "random" is what'sin question
here.If you keep adding bits to the shift register
length you will quickly reacha point at which the
repeat interval (assuming you put the feedback taps
inthe right place) is far beyond a single human
lifespan. If we can all agreethat that is random, then
the cutoff point between psuedo-random and randomis
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 JrSent: Wednesday, September
29, 2004 3:12 PMTo: Rainer Buchty; MetrophageCc:
synth-diy at dropmix.xs4all.nlSubject: Re: [sdiy] VERY
cool/bizarre: Buchla noiseI still don't agree... It is
NOT truly randomas 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...
thelowest frequency it can generate would
be1111000011110000  etc...the highest
is1010101010101010The all ones (or zeros depending on
the logic) statewill latch the device and it must be
avoided orrecovered from.It approaches 'random' and
over the short term(compared to other methods) is a
good way to generatenoise - as long as you don't
recognise that itIS 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
shiftregister) is truerandom but shows a periodic
behavior. That's why youshould use at least22, 23 Bits
so that pattern repeat takes place inthe domain of a
fewminutes rather than seconds.Rainer