Method for inharmonic tone generation using a coupled mode digital filter
AssigneeStanford University
InventorScott A. Van Duyne
Life of this patent
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Abstract
A coupled mode digital filter which simulates any number of arbitrarily tuned modes coupled together so as to share the same loss element at a junction loaded by an arbitrary impedance function is formed from the combination of one first order allpass filter 28! and one unit delay 30! per mode and one shared coupling filter36!. This coupled mode digital filter may be excited by a stored or generated excitation signal, or a filtered excitation signal, to produce inharmonic percussive sounds and musically interesting two-stage and beating decay envelopes resulting from natural coupling of modes of near frequencies
Claims17
A coupled mode digital filter comprising:
- a mode oscillator loop comprising a allpass filter and a delay, wherein the allpass filter is in series with the delay, wherein the mode oscillator loop is a negative feedback loop, and wherein the mode oscillator loop has a resonant mode at frequency f;
- and
- a coupling filter adapted to attenuate signals at frequency f by a predetermined attenuation factor;
- wherein the mode oscillator loop and the coupling filter are connected in series to form a positive feedback closed loop structure.
A coupled mode digital filter comprising:
- a collection of m mode oscillator loops comprising respective m first order allpass filters and respective m unit delays, wherein the mode oscillator loops have respective m resonant modes at frequencies f.sub.1, f.sub.2, . . . , f.sub.m, ;
- and
- a coupling filter adapted to attenuate signals at s frequencies f.sub.1, f.sub.2, . . . , f.sub.m, by predetermined attenuation factors A.sub.1, A.sub.2, . . . , A.sub.m ;
- wherein the coupling filter and the collection of m mode oscillator loops form a closed loop structure.
Dependencies are inferred from the claim text.