The recorded sine-sweep is deconvolved into the IR. Fons Adriaensen has a linux program called 'aliki' that works on this principle. Sine-sweeps give you a better signal-to-noise ratio as compared to popping balloons etc.. 
Apple releases an IR utility that is very easy to use:
http://manuals.info.apple.com/en/Impulse_Response_Utility_User_Manual.pdf
not sure if you need to buy Logic for this one.
One should be able to build a tool with csound if one knows how to do the deconvolution. 
Over to you, Richard Dobson?

cheers

Georg


-----Original Message-----
From: Michael Gogins [mailto:gogins@pipeline.com]
Sent: Mon 31/03/2008 16:24
To: csound@lists.bath.ac.uk
Subject: [Csnd] Re: Re: Re: Re: Re: Re: Top Quality Reverb
 
I don't know the details, but I now that useful impulse responses can be made by recording by recording the response to sweeping a loudish sine tone from lowest audible to highest audible frequency in the space. How that is processed to create an impulse I don't know, probably simply by doing a Fourier analysis of the entire recording. After all, the notional "impulse" is a Dirac delta, a signal of zero duration and infinite amplitude thus containing all frequencies at equal amplitude, and the sine sweep obviously contains all frequencies of interest at equal amplitude.

Another method of deriving the impulse response would be to record the response of the space to a maximum length sequence, a type of noise containing every sample that can be expressed in the word length. The impulse response can be computed from the recorded response by taking its circular cross-correlation with the original sequence. I don't know if anyone actually does this... the MLS for a CD quality recording would be about 24 seconds long.

Regards,
Mike

-----Original Message-----
>From: Anthony Palomba 
>Sent: Mar 31, 2008 10:58 AM
>To: csound@lists.bath.ac.uk
>Subject: [Csnd] Re: Re: Re: Re: Re: Top Quality Reverb
>
>Wow that is pretty cool. I am curious to know how 
>I would make my own impulses. Are they just processed
>field recordings of an isolated sound within that space?
>
>
>
>Anthony
>
>  ----- Original Message ----- 
>  From: peiman khosravi 
>  To: csound@lists.bath.ac.uk 
>  Sent: Monday, March 31, 2008 7:28 AM
>  Subject: [Csnd] Re: Re: Re: Re: Top Quality Reverb
>
>
>  http://www.xs4all.nl/~fokkie/IR.htm
>
>
>  On 31 Mar 2008, at 14:24, Panos Katergiathis wrote:
>
>    I was about to ask that myself...
>
>
>    Anthony Palomba wrote:
>      Where can I get interesting impulse responses of different spaces?
>      Anthony
>
>
>
>
>    Send bugs reports to this list.
>    To unsubscribe, send email sympa@lists.bath.ac.uk with body "unsubscribe csound"
>
>
>Send bugs reports to this list.
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Boenn G (CCI) wrote:
> 
> The recorded sine-sweep is deconvolved into the IR. Fons Adriaensen has 
> a linux program called 'aliki' that works on this principle. Sine-sweeps 
> give you a better signal-to-noise ratio as compared to popping balloons 
> etc..
> 
> Apple releases an IR utility that is very easy to use:
> http://manuals.info.apple.com/en/Impulse_Response_Utility_User_Manual.pdf
> not sure if you need to buy Logic for this one.
> One should be able to build a tool with csound if one knows how to do 
> the deconvolution.
> Over to you, Richard Dobson?
> 
> cheers
> 
> Georg
> 

Er, who, me? I don't know anything about deconvolution other than it 
exists. Angelo Farina (on sursound list) is the expert; the responses in 
the Waves IR1 system are obtained by his method. I have however just 
ordered Logic, so I will actually be able to play with that utility.

I rather liked the idea of balloons. Balloons have personality. Seems to 
me, the combination of balloons and the Zoom H2 pocketsized surround 
recorder would enable spontaneous and seredipitous IR recordings without 
being weighed down by Tons Of Stuff, and hence, as far as such things 
can be, unobtrusive.

Richard Dobson

Angelo just published on convolution in an AES paper.

http://emusician.com/tutorials/emusic_acting_impulse/

has the goods on free Windows software that works.

You can also find lots of IRs around the net.

Michael




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