[sdiy] Digital noise generation

[Scott Gravenhorst]

Antti Huovilainen <ajhuovil at cc.hut.fi> wrote:
>Hi again
>
>I partially solved the problem. Using any two tap noise generator sounded 
>quite bad, but testing with 24 bit 4 tap generator produced much better 
>results. If anyone has insight to why this is so, please tell.

Insight, no, IMO, they should sound nearly the same, (and I'll bet they do
in a hardware implementation) as long as the length of the sequence is
maximum.  In hardware, I thought about using the 2 tap method, but either 4
or 2 taps requires on quad XOR gate package anyway (and even with the 4 tap
method only 3 XOR gates are used for the taps so one gate is left over to
act as an inverter).  I've always opted to include the extra flip flop and
use 4 taps.

>I have uploaded the matlab code and example wavs to
>http://www.acoustics.hut.fi/~ajhuovil/noise/
>
>goodnoise.wav = 24 bit 4 tap noise
>badnoise.wav = 23 bit 2 tap noise
>rand.wav = matlab's internal random number generator. This one still 
>sounds slightly smoother than goodnoise.wav.
>
>Antti
>
>"No boom today. Boom tomorrow. There's always a boom tomorrow"
>   -- Lt. Cmdr. Ivanova
>

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