[sdiy] Digital noise generation

[Magnus Danielson]

From: Antti Huovilainen <ajhuovil at cc.hut.fi>
Subject: [sdiy] Digital noise generation
Date: Tue, 8 Mar 2005 18:20:35 +0200 (EET)
Message-ID: <Pine.OSF.4.61.0503081817450.2284 at kosh.hut.fi>

> Hello

Hi Antii,

> I recently did some tests in matlab emulating a feedback shift register 
> noise generator. However, the noise sounded quite bad with frequent 
> "snaps", mostly independent of shift register length. I tried both using 
> the noise as-is (clocked at 44khz) or downsampled (clocked between
> 200khz - 1mhz).

I assume you meant 200 kHz to 1 MHz.

> What methods do you people use to generate noise digitally? (to avoid 
> selecting transistors and worrying about interference with high gain amps)

What polynomials did you use?
If you dig in the Synth-DIY archive I published a list up to length of 64.

Did you use a parallelized version?
I can help you with that if you need.

Did you amplitude weigthed the outputs of the parallelized version? 
Again, I can help you, but it is really a quick-and-dirty approximation of
filtering with a one-pole lowpass filter. Exponential drop-off in amplitude
should work the "older" the bit is supposed to be.

Cheers,
Magnus