Re: [linux-audio-dev] Gong physical model (was: LADPSA v1.1 SDK Provisional Release#)

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Subject: Re: [linux-audio-dev] Gong physical model (was: LADPSA v1.1 SDK Provisional Release#)
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Tue Aug 20 2002 - 11:41:58 EEST


On Fri, Jul 26, 2002 at 02:10:12 +0200, David Olofson wrote:
> > and a gong physical model (very similar code).
>
> Now *that* sounds interesting. What synthesize method(s) is it based
> on? Purely real time? Any interesting documents to read?

Its a waveguide mesh. Actually there is a small bug in the released
version that makes it less resonant than it should be.

The key part is the non linear filters that introduce in inharmonicities
at waveguide boundaries. To get a gong sound you can describe the
appripriate physical parameters (quite large, fairly different deflection
characteristics for each sign) and excite it with a single cycle of a
low frequency sine wave (to simulate the stroke of the beater).

If you wanted a cymbal I would guess the deflection characteristics would
still be different, the size would be smaller and the excitation function
would be more like an enveloped noise burst (depend on what you strike it
with - I'm thinking of one of those brush things).

I have also written a program that lets you describe arbitrary waveguide
meshes and will generate C from them.

N.B. the cpu cost is quite high - comparable to a short reverb, but it
would be possible to precompute it.

There is a paper about it, but I don't have it at the momnet.

- Steve


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