----- 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

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Hi Anthony,

Pretty much.  Typically IR's aren't processed heavily, if at all.  Attention is paid 
to what sound source is chosen, and how it's recorded.  Usually the sound/recording 
engineer will set up a microphone at the location for which the IR is desired 
(different locations in a space will give a different IR).  Then a sound source 
creates an impulse at the location where the sound should be coming from (e.g. 
onstage in a concert hall).

Much of the quality of the IR depends upon the nature of the sound source and the 
recording setup.  For the source, you want an impulse, i.e. a very short burst of 
equal energy across the entire frequency spectrum.  Common sound sources are starter 
pistols or slapsticks (which I've always found to be be quite colored, but they'll 
work in a pinch).

For making the recording, you want to use an omnidirectional setup, in order to 
capture all the reflections coming from different sides.  If creating a realistic 
response is a goal (and you can use a stereo IR), a good binaural mic is usually a 
first choice.  If one isn't available, any simple omni mic would do.

Once you've got the recording gear set up and levels adjusted, you simply need to 
record a burst from the chosen sound source.  Note that this often requires more than 
one person, since if you're monitoring the recording you probably won't be the one 
producing the impulse.  That's about all there is to it (other than practice and 
experience, of course).

Good recording conditions are essential.  Any sound other than the desired impulse 
will color your IR and appear any time you convolve it.  Several years ago I was 
trying to record an IR of a stairwell in the music building here, and was simply 
unable to get a recording that didn't have some extraneous noise somewhere (e.g. door 
opening, voices outside, etc).  Although as an effect it was interesting, for a clean 
reverb the recordings were essentially useless.  I took the best response I had and 
tried to completely remove a small squeak at the tail end, and despite my best 
efforts either the squeak was audible in the IR, or the reverb tail sounded strongly 
processed and unnatural.

Some commercial convolution reverbs require that the impulse be in their proprietary 
format, but usually that's just an intermediate step after running the impulse 
through a (series of) Fourier transform(s).  It's just like the .cv files used by 
csound's convolve opcode.  You probably can't produce one of those without licensing 
software from the manufacturer.  Most popular reverbs will let you use an audio 
sample, though, so you shouldn't need to worry about it.

John W. Lato
Sarah and Ernest Butler School of Music
The University of Texas at Austin
1 University Station E3100
Austin, TX 78712-0435
(512) 232-2090

Anthony Palomba wrote:
> 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"
> 

John Lato wrote:
> Hi Anthony,
> 
>..
> 
> Some commercial convolution reverbs require that the impulse be in their 
> proprietary format, but usually that's just an intermediate step after 
> running the impulse through a (series of) Fourier transform(s).  It's 
> just like the .cv files used by csound's convolve opcode.  You probably 
> can't produce one of those without licensing software from the 
> manufacturer.  


It is surprising how often these proprietary formats prove to be plain 
wave or aiff files with a diffferent extension. It is always worth 
viewing them in a hex editor to check. I seem to recall one case where 
some trivial change to the header was all that was done, easily seen and 
changed to make it a plain soundfile. And presumably vice versa.


Richard Dobson