From: Carl Hetherington (lists_at_carlh.net)
Date: 11/25/03 11:44 EST
From: Carl Hetherington <lists@carlh.net> Subject: Re: [Ardour-users] Re: good quality reverb - brutefir! Message-ID: <Pine.WNT.4.58.0311251637280.1252@renato> Date: Tue, 25 Nov 2003 16:44:33 +0000 (GMT Standard Time) [snip] > > 1. Use something that is "good enough" --- e.g. a gun shot (probably > > best not to use this in a church) or a high-quality loudspeaker. > > I was thinking about this earlier today - I'm a drummer so I've got lots > of things that could be used to produce such sharp, noisy signals. > Seems like that'd be a fun thing to play with. I think the main problem with approximating impulses is that you don't get much energy into the room, so your signal-to-noise ratio is likely to be poor. > > 2. Swept sines --- you can make a good stab at measuring the impulse > > response by measuring the response of the room to a varying sine wave and > > doing some jiggery-pokery. > > Do you really need the jiggery-pokery? The nice thing about the delta > function is that it captures *all* the frequencies and the IRs will > capture the rooms response to all of them. But of course we can't > actually generate a delta function. > > So it occurs to me sweeping from 0Hz to 24kHz will capture the response > of all the frequencies people will be able to hear. So, if we apply the > reverb filter to audio, and we miss frequencies that are inaudible, who > really cares? Yes, I think you're right. > > 3. Pseudo-random binary sequences / Golay codes --- a bit complicated to > > go into here but essentially you use a pre-defined but noise-like signal > > and do some maths. > > Hmmm, not an application of coding theory I'd have guessed... > What does this approach win us? It seems to me that the sine-sweep is > really where it's at for audio. Using Golay codes seems like a lot of > work. I'd have to look up the relative merits of sine sweeps against pseudo-random binary sequences. AFAICR there are pros and cons to each method. PRBS methods are not that hard once you get into them ;-) > > One commercial gadget that uses these principles is the Yamaha SREV > > http://www.soundcorp.com.au/html/yamaha_srev.htm > > I'm sure there are others. > > I seem to recall a discussion on lau recently about sine-wave sweep > generation. I'll dig into the archives and try to find some free > software to do things like this. There are certainly lots of journal papers about these techniques from which you could write software to do it all. Cheers Carl ------------------------------------------------------- This SF.net email is sponsored by: SF.net Giveback Program. Does SourceForge.net help you be more productive? Does it help you create better code? SHARE THE LOVE, and help us help YOU! Click Here: http://sourceforge.net/donate/ _______________________________________________ Ardour-users mailing list Ardour-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ardour-users
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