[sdiy] Best software noise algorithm?

[Harry Bissell]

what ...tick... could be more ...tick... annoying ...tick...
than the ...tick... MM5837 ...tick...

H^) harry

----- Original Message -----
From: Scott Nordlund <gsn10 at hotmail.com>
To: synth-diy at dropmix.xs4all.nl
Sent: Wed, 17 Feb 2010 15:01:35 -0500 (EST)
Subject: RE: [sdiy] Best software noise algorithm?


Certain older digital synths had some interesting ways of faking 
"noise".  The Casio CZ series and Yamaha OPL chips seemed to do 
some sort of crazy phase modulation feedback, and the Ensoniq ESQ-1 
used nasty single cycle waveforms with the recommendation that they
be pitch modulated for lots of aliasing.

But I'm sure these are not efficient OR spectrally pure.  Probably
less irritating than the MM5837, anyway.

----------------------------------------
> To: synth-diy at dropmix.xs4all.nl
> From: tom at electricdruid.net
> Date: Wed, 17 Feb 2010 18:01:19 +0000
> Subject: [sdiy] Best software noise algorithm?
>
> Hi All,
>
> What's the most efficient software pseudo-random noise algorithm?
>
> I have previously used LFSRs, which are reasonably quick and can
> produce very long sequences quite easily, but I'm looking for
> something really quick and dirty.
>
> I looked into Linear Congruential Generators, and found lots of sites
> that said that these can be very quick if you ensure the modulus is a
> power of two. But most examples are actually with the Parks-Miller
> numbers, which aren't a power of two.
>
> I'll be doing this in dsPIC assembly as usual, and I've currently got
> a 64-bit LFSR that generates a new 16-bit number in 19 cycles. The
> quality and sequence length of that are more than I really need, so
> I'd like to speed it up.
>
> Have people got any good tricks to share for making random numbers
> quickly ?
>
> Thanks,
> Tom
>
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-- 
Harry Bissell & Nora Abdullah 4eva