[LAD] Attenuation of sounds in 3D space

[Jörn Nettingsmeier]

On 07/22/2010 08:42 PM, Ralf Mardorf wrote:

> As an ape (of course I'm an ape like every human is an ape) and troll (I
> don't see myself as a troll) I suspect phasing too, that's why I
> overstated argued with the next generation Cochlea-Implant, or needles
> in the brain.

that is a bogus statement. phasing happens in the brain as well. just 
put on your favourite pair of headphones and wire one side out-of-phase. 
instant nausea. (of course, if you keep it on for a few days, your brain 
will adapt - presto: you'll be hurling all over the real world when you 
finally put them down.)

> Visual 3D, by a surround projection + 3D glasses isn't perfect, but
> there is just one picture and not several pictures that needs to be
> phase synced in the eye.  Perhaps a week analogy.

a terribly chosen analogy indeed. since when do the eyes care what phase 
an incoming photon is? unless you're staring into a laser, each photon 
will have totally random phase.
next error: there *are* two images, and they do need to be synced. phase 
is irrelevant, though.

> When having 4 or 8 or more speakers I fear phasing at the position of
> the ears. But perhaps it isn't that much. I'll try to listen to
> ambisoncs :).

you can get terrible phasing, and not just in the center, but pretty 
much everywhere. that's why some people stagger the timings of the 
loudspeakers a bit, to smear out the phasing until it is more or less 
masked by the content.
but it should be noted that stereo has the very same problem. now if 
method A produces a 60° soundstage with phasing at N units of 
obnoxiousness, a method that produces 360° surround is entitled to 6N 
UoO phasing. in practice, ambisonics does better than this, but there is 
no denying the issue.
one thing that often gets overlooked: people have learned to accept 
stereo (or, in some circles, 5.1) as the gold standard, and its 
shortcomings have grown into desired features. it's very hard to compete 
with a method that does a few things very well and doesn't even try to 
reproduce most of the auditory cues of, say, a live experience.

the main ingredient that makes any sound reproduction system sound good 
is your brain. the trick is to nudge it into sympathy with carefully 
chosen cues.