[sdiy] Akai S612 filter/schematics

[Andre Majorel]

On 2002-04-18 13:36 +0200, Theo wrote:

> > The frequencies of the partials were set by raising a number to
> > a random power. I think this is a pink distribution (i.e.
> > statistically, each octave contains as many partials as any
> > other octave).
>
> Ok I see what you mean now.
> Your energy distribution is right but I think your frequency
> distribution is different from pink noise.
> For better sonic result you might try having the partials distributed
> "linear" and use 1/f for the amplitude.
> Also the higher the octave the more partials, but keep the energy
> distribution.

Interesting, I've got to try it. However, without thinking it
out, I'm afraid it would mean more partials to compute for the
same subjective noise density, especially in the higher octaves.

Mmm, suppose for instance that you want to generate pink noise
between 100 Hz and 12.8 kHz (7 octaves), with 1000 partials in
the band between 1.6 kHz and 3.2 kHz (because that's more or
less where the frequency resolution of the ear is highest).

With a logarithmic distribution, you need

  7 * 1000 = 7000

partials. With a linear distribution, you need

  (12800-100)/(3200-1600) * 1000 = 7938

partials. OK, just 13% more, but the gap would widen if we
compared against a weighted logarithmic distribution (where the
density follows the ear's frequency resolution).

> I've been using similar code to for "additive" synthesis where each
> "partial" is a small noise band instead of a sine.
> So far I only can generate static sounds, but sending them thru some
> effects makes nice atmospheres.
> Sonically they sit in the spooky category.

I'd like to hear what it sounds like. What band width did you
use ?

-- 
André Majorel <URL:http://www.teaser.fr/~amajorel/>
std::disclaimer ("Not speaking for my employer");