[music-dsp] Resonant filters

[David Olofson]

On Monday 23 February 2004 18.35, Alex Raider wrote:
> [skip : what is resonant filters]
>
> > Same thing as a resonance in electronics or even a wine glass.
> > Just a peak in the frequency response.
> > A two-pole IIR resonantor for example...
> > kinda like a bandpass....
>
> Wow.
> I suppose I can implement resonant filters using IIR?

Yes. Doesn't really matter what kind of filter you're using; the point 
is that there is a feedback loop that makes the filter resonate.

Pump up the resonance (feedback strength) and you've got an 
oscillator. :-)


> Where from name comes? Something like old analog RLC design?

What name? A resonant filter is... well, resonant! ;-) IIR means 
Infinite Impulse Response. IIR filters use some form of iterative 
algorithm, and generally have exponential impulse responses, as 
opposed to FIR (Finite Impulse Response) filters, where an impulse 
only affects the output within a strictly define time frame.

IIR filters are (theoretically) the closest match to the common types 
of analog filters, though FIR approximations are often used instead, 
when dealing with very steep and/or generally complex filters. IIR 
filters are very fast and simple for relatively simple filters, 
though, and they have the major advantage of not consuming tons of 
cycles (large windows) when dealing with low frequencies.


//David Olofson - Programmer, Composer, Open Source Advocate

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