Been quiet lately... too much DIY ?

[Paul Wilkinson]

Take all this with a grain of salt.

The only way to convincing position a sound is to position it at or between
speakers.  It's true that with good stereos the sound has height and goes
past the limits of the speakers. (In my experience this is where records are
better than CD's.)  But this extra range is very difficult to control.

3D position is simulated using phase (which is really delay) and filters
that simulate what your head and ears do to sound coming from behind you
(head related transfer functions, or HRTF's).

The problem in a nutshell is this:  Something on your right is heard with
both ears.  So any simulation has to play it out of both speakers.  But then
you hear both speakers out of both ears, so you have 4 signals at work.  In
a perfect world you'd arrange these signals so that they cancelled out the
difference between the 4 signals and the 2 you really want.  But as soon as
you add room acoustics it's easy to see how impossible this is.  And then
there's the differences between peoples' systems ...

I do video game audio programming for a living so I have plenty of
experience with 3D sound simulation (like QSound, SBLive).  None of it
provides convincing positional placement, although it does increase the size
of the stereo image.  If this is what you want, then you're in luck.  But if
you want to whip a sound around somebody's head you'll have to resort to
extra speakers and use the effect only in performance.  And that's good
enough for me.  Let's do it!

- Paul


------Original Message------
From: Doug Tymofichuk <dougt at cancerboard.ab.ca>
To: Synth-DIY <synth-diy at node12b53.a2000.nl>
Sent: May 30, 2000 9:23:18 PM GMT
Subject: Re: Been quiet lately... too much DIY ?



On Tue, 30 May 2000 15:56:35 -0400 (EDT) Paul Wilkinson
<synthdiy at mail.com> wrote:

> When I talk about 3D sound I really mean 2D.  And 2D is
> enough for me.  Does "true 3D" mean you can fade vertically
> as well?
>
> Come to think of it, being able to fade vertically as well
> (and make that 3 active processors) would be pretty cool.
>
> Damn it I don't think I'm going to sleep tonight.  Yes I'm
> interested.
>
> - Paul
>
How in the world does one move a sound vertically? I know
that a decent stereo system can project sounds that way,
but what is the trick to doing it manually? Some kind of
phase shift? This sounds like a lot of fun, especially if
it can be done all analogue.

----------------------
Doug Tymofichuk
dougt at cancerboard.ab.ca

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