Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!decwrl!labrea!aurora!eos!ames!pasteur!agate!saturn!ucscb.UCSC.EDU!lupin3
From: lupin3@ucscb.UCSC.EDU (-=/ Larry Hastings /=-)
Newsgroups: comp.sys.amiga
Subject: Re: Sonic Tomfoolery
Message-ID: <2102@saturn.ucsc.edu>
Date: 25 Feb 88 10:40:44 GMT
References: <319@ardent.UUCP>
Sender: usenet@saturn.ucsc.edu
Reply-To: lupin3@ucscb.UCSC.EDU (-=/ Larry Hastings /=-)
Organization: Uncle Charlie's Summer Camp (UC Santa Cruz)
Lines: 46
Keywords: Hah.  Good question; deserves good answer.

+-In article <319@ardent.UUCP>, rap@ardent.UUCP (Rob Peck) wrote:-
+----------
|
| We have two ears, and two output channels to fool with on the Amiga.
| Each of the stereo channels has two real hardware channels feeding
| into it.  If I hack the audiotools to add the stereo support
| that I need for a coming hack, I can send the same sound to
| a left and right channel at the same time, one at a higher volume
| and the other at a lower volume, moving the sound from left to
| right as the volume is modified on both channels simultaneously.
| 
| Then, not only control the volume, but also control the phasing
| between the two channels a little bit so as to create a distance
| perception "somewhere out there in front of me to the left or the
| right".
| 
| But what kind of controls must I apply to make the sound appear
| to be "behind me"?????
| 
| Rob Peck			...ihnp4!hplabs!ardent!rap
|
+----------

  This is a little trickier.  (This is also the reason that your phasing trick
appears to make the sound "in front of me", rather than "either in front of
or behind me".)
  The way that us Human Beengs tell if a sound is in front of, or behind of, us
is because of those big funny-looking things that hang on the outside of our
heads, holding our glasses up.  Yep, the actual exterior part of the ear. You
see, when something is behind you, the outer ear runs a little interference and
changes the spectral makeup of the sound slightly, you compare it to a similar
sound you've heard before and decide "it's the same sound as THIS, it's just
behind me".
  Professor Muma (my teacher for History of Electronic Music) went off on a
side note about this once; it seems he and an associate did some research on
the exact subject.  (He stuck small mikes in his ears, and they played identical
sounds at 12 different positions around his head, and did a spectral analysis of
all the results.)  I suppose I could ask him for more info if someone is REAL
interested... but methinks it would be a _major_ pain.  Who knows, it could
be real easy; but I suspect the former...

  By the way, he also quickly mentioned that humans can tell _height_ of a sound
as well; the problem being that this is a) a learned trait, and b) something
that us civilization dwellers don't really need to learn well.  (Aboriginies
(sp!), he said, could tell the height of a sound amazingly well...)  He didn't
explain how height was detected...