Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!pasteur!ucbvax!CORY.BERKELEY.EDU!dillon
From: dillon@CORY.BERKELEY.EDU (Matt Dillon)
Newsgroups: comp.sys.amiga
Subject: Re: Sonic Tomfoolery
Message-ID: <8802282339.AA11044@cory>
Date: 28 Feb 88 23:39:45 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 47

:In article <719@ur-cvsvax.UUCP>, jea@ur-cvsvax.UUCP (Joanne Albano) writes:
:> In article <8802251858.AA21577@cory.Berkeley.EDU>, dillon@CORY.BERKELEY.EDU (Matt Dillon) writes:
:> > >You're working too hard - the human ear has no mechanism for detection of
:> > >phase.
:> > 	
:> > 	Huh, where did this come from?  I've played around with sound
:> > quite a bit, and if I generate two tones of slightly different frequencies,
:> > I can hear the phase quite fine thank you.
:
:That's not 'detection of phase', that's detection of two tones of slightly
:different frequencies.  It's not the same thing at all.  Two tones of
:slightly different frequencies will create a 'beat' between them, which
:will sound like the tones are quickly increasing and decreasing in
:volume.  The 'phase' here is two tones of the _same_ frequency, but with 
:one slightly leading or lagging the other.  Here I'd have to agree with
:Matt, we can't detect that nearly as readily.  

	What I meant was, let's say I generated two tones of 1Khz and
1.00001Khz.  The beat frequency is .001 hz, and thus slow enough that
it doesn't effect the experiment.

	Now, what I am hearing at a MOMENT in time is the SAME frequency
generated twice, one slightly out of phase with the other, and the phase
changing slowly.  I can HEAR the phase changing.  I can HEAR the volume
get lower as it approaches 180 degrees, etc...

	Now, take two generators of the same frequency (say, 1Khz).
place them out of phase at some phase angle.  This continuous static
phase angle is equivalent to what I heard for a moment in the latter
experiment.  If you then change the phase angle to something else, it is
equivalent to what I heard for another moment in the latter experiment.
I can readily hear the difference between the two phases, though it
would be extremely difficult to tell which 'sound' is what phase angle.
Generally, it is quite easily to tell that there is *some* phase because
such tones are distinctly different than a pure tone.

	If your two tones are comming from physically different areas,
then the phase entering your ears may become quite complex, and depend
on the placement of your head.  For instance, your right ear may be hearing
1Khz@30 degrees, and your left ear may be hearing 1Khz@60 degrees.  If
you isolate your ears so each ear 'hears' only one of the generators,
you would hear just one phase 1Khz@X degrees.  But I'm getting beyond
my knowledge here.  I don't *think* the brain syncs up two tones comming
in uniquely one to each ear.  Besides, I don't think the original poster
was thinking of ear-isolation in his posting.

					-Matt