[sdiy] Best software noise algorithm?

[Neil Johnson]

two ...tick...tick... MM5837s ...tick...tick... ??? ...tick... ???

(actually, I think it chuffs rather than ticks)


On 17 Feb 2010, at 21:06, Harry Bissell wrote:

> 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
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