[sdiy] digital noise band generator?

[Matthew Smith]

Quoth Paul Perry at 25/08/11 13:11...
> 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!

I sure ain't one for Hard Sums, but if asked to code something up, I'd 
probably start with a linear feedback shift register (I'd imagine 
they're fairly easy to implement in C - I've only done them in Verilog,) 
take selected bits of that as your input to the next stage, and then use 
  something like a state variable filter (or HPF after LPF) as described 
by Chamberlain (assuming you have a copy of that.)

If you choose a microcontroller with a built-in ADC, you can hook up 
some pots to set filter parameters - a bit less complex than LCDs and 
rotary encoders, unless you've already got a library for those to hand.

I'll be mucking around with something similar, although I'll be using a 
CPLD or FPGA to do the number crunching (parallel operations and 
arbitrary data widths) with parameter registers set by SPI control.

Cheers

M

-- 
Matthew Smith

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