Re: [Ardour-users] good quality reverb on linux

From: Ross Vandegrift (ross_at_willow.seitz.com)
Date: 11/19/03 08:50 EST


From: Ross Vandegrift <ross@willow.seitz.com>
Subject: Re: [Ardour-users] good quality reverb on linux
Message-ID: <20031119135049.GA20260@willow.seitz.com>
Date: Wed, 19 Nov 2003 08:50:49 -0500

(I've CCed ardour-users again - I'll let anyone on the list who knows
more correct my explanation below)

On Wed, Nov 19, 2003 at 12:30:01AM -0600, Third Option wrote:
> how does this relate to audio?  is it that a convoluted (no pun intended)
> algorhythm might be used to generate something such as a reverb?  wait I can
> almost understand that - the original sound waves would overlap with the new
> versions being bounced back...overlapping...uhm...

Well, if you really want to know how it relates to audio, you'd have to
ask an electrical engineer - they're the guys who do signal processing
type stuff.  I have a friend in that, and man, he's all about
convolution ::-).

However, here's my gut reaction:  First, an audio signal can be through of
as a mathematical function.  When everyone's talking about "impulses", they
must be talking about some other function (cause you need to functions if you
want to convolute).

Since we're trying to get reverb, the impulse function must define some
kind of "reverbness" of a room somewhere.  I guess if you recorded a
sound in a room, and sort of removed the original sound, you might get a
profile of how the reverb in the room sounded.

(Side digression: I suppose the signal that remains after removing your
test sound is a bunch of impuse/delta functions in the transformed
space?  That would explain the name...)

Now, if you take that profile and blend it with another signal, I can see
how it might end up applying that room's reverb to your new signal.  The
mathematical mechanics of this probably have to do with the resonance
that results in a periodic function if you "hit it" with a delta
function, but this is getting a little too much into differential
equations for 9am ::-)

Of course, you'd need to do a really good job of removing the original
sound you used - otherwise you might hear it in your reverbed audio.  I
suspect that's what the guys are talking about when they say they want
"good impulses" - that is, high quality samples of the signal.  Well,
and samples taken in a room that sounds good!

Hopefully this clears it up somewhat...

-- 
Ross Vandegrift
ross@willow.seitz.com

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He Blesses it.                                 It is a Holy Holy-Water Cannon.
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He has it pierced.                It is a Holey Wholly Holy Holy-Water Cannon.
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