posted 31 January 2001 11:48            

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I have been trying to work out the simplest most elegant algorithm to do convolution of a sample file with another short sample file as an impulse response. Previously I've used a program called SoundHack to do this--but not in real time. I came up with a way that would work using triggered sample and hold, sequential single sample delays and multiplication, but it's frightfully expensive computationally, as there would have to be as many submodules as there are samples in the IR sample file. Is there any easy way to do this without creating such a gigantic tree of modules?

MJ

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posted 31 January 2001 13:01            

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One way to do short-term convolution in the time domain is to *multiply* in the frequency domain. See the example called Talking Forced Air Heater in the Cross-synthesis/Spectral folder of the Kyma Sound Library.

This is not the way to do reverberation using convolution, but it is a way to cross the spectral envelope of one Sound with the spectrum of another one.

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posted 31 January 2001 16:22            

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Yeah, that's definitely cool, but the artifacts from the Fourier transform lend sounds a particular quality, you know the one I mean. Clangy from the phase distortions.
It was the reverberation variety that I was so keen on. I used convolution to amazing effect as follows: Took a sample file of a super-dry and unresonant plucked-string sound direct from my Yamaha EX5's physical modeling engine and convolved it in SoundHack with the sound of knuckles rapping the back of an acoustic guitar. The product was an astonishingly realistic (albeit WIERD) stringed instrument.
-MJ

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posted 31 January 2001 17:32            

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No easy way to do that in Kyma right now, but it's on our wish list.

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posted 03 February 2001 11:10            

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Not to direct you away from Kyma, but if you have access to a PC (I am assuming that you are using MAC for sound hack) Sonic Foundry sells a Convolution program "Accoustic Mirror" for about $59 that comes with several hundred impulse files.

You can also try this for free id you download their Sound Forge public beta. You won't get all the impulse files, but still an amazing realtime tool. http://www.sonicfoundry.com/download/step2.asp?DID=257
Accoustic mirror also comes with the tools to create excellent impulses of you own.

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posted 05 February 2001 13:13            

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Thanks Preston,

I will definitely check that out.

--MJ

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