[sdiy] digital noise band generator?

[Magnus Danielson]

On 25/08/11 05:41, Paul Perry wrote:
> I expect that there may be a simple (algorithm running on micro) way to
> generate a band of white noise.
> And maybe even a way to dial in a few parameters to tune it.
> I must confess that my immediate need is to aid a friend suffering from
> tinnitus, but doubtless it would be a handy thing to have in a modular
> rack!
>
> OK, I'll probably end up with a standard noise source and analog filters
> - but I am curious to hear what the algorithmists have to say.

Another approach is this:

1) Suitable white noise source of choice, such as those mentioned.
2) Lowpass filter to suitable width
3) Phase or frequency modulate an oscillator with that noise, with a 
high modulation index (to supress carrier)

Considering that a phase-accumulator based oscillator is very cheap in 
digital implementation and that phase or frequency modulation is a 
matter of where the signal is added, the modulation part is easy.

Waveshaping to sine can be done using naive lookup table or possibly 
phase interpolation if you want something better.

Ring-modulation (multiplication of noise and carrier) has the downside 
of creating sum and difference frequencies, but in this case it would 
only create the two side bands of the carrier. However, this would only 
be a variation of the above scheme... so you can build the same basic 
building-blocks and then try yourself what works best for you.

Cheers,
Magnus