[sdiy] Resonator type filters

[rburnett at richieburnett.co.uk]

> Mostly, we're trying to simulate certain resonances that occur in the
> bodies instruments (brass/woodwind/strings/etc) and there aren't 30+
> of those.

Playing devils advocate there are an infinite number of modes for a 3D 
mechanical structure.  Sure enough there will be some prominent 
resonances and those modes will dominate the perceived characteristics 
of that instrument's body.  But if you look at the fine detail, there 
will be many complex peaks and dips as various components of the 
structure resonate at different frequencies and energy is exchanged 
between them at different rates, resulting in frequency splitting, etc.

If you don't believe me, try striking the sound board of an acoustic 
guitar and recording the noise that the instrument emits using a 
microphone nearby.  Then look at the spectrum with Goldwave, Audacity, 
MATLAB, whatever.  You won't just see four or five peaks, you will see a 
very complex spectrum from this simple impulse test.  How accurately you 
actually need to model this complex frequency response is up for debate.

-Richie,