Path: utzoo!mnetor!uunet!unisoft!hoptoad!xanth!kent
From: kent@xanth.cs.odu.edu (Kent Paul Dolan)
Newsgroups: comp.sys.amiga
Subject: Re: Sonic Tomfoolery
Message-ID: <4292@xanth.cs.odu.edu>
Date: 29 Feb 88 02:43:37 GMT
References: <8802251858.AA21577@cory.Berkeley.EDU> <719@ur-cvsvax.UUCP> <7233@cisunx.UUCP>
Reply-To: kent@xanth.UUCP (Kent Paul Dolan)
Organization: Old Dominion University, Norfolk Va.
Lines: 41
Summary: No phase?  Don't believe it!

In article <7233@cisunx.UUCP> ejkst@cisunx.UUCP (Eric J. Kennedy) writes:
>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.  

I don't think so!  I remember reading many years ago that although the
human ear can only hear pitches up to about 20,000 Hz, that a stereo
system, to maintain fidelity enough to allow a listener to pick out
the second violinist playing half a tone flat in a symphony recording,
had to keep the left and right channel phase relationship correct to
the equivalent of 200,000Hz, because the human brain, processing the
audio signals, is that sensitive to phase relationships.  I believe
the math can be done to prove this with a pocket calculator and a back
of the envelope diagram of a symphony hall and a schematic human head.

Certainly, given a choice between believing I detect directions that
closely by the amplitude difference or by the phase difference, I'll
go for phase on intuition alone.

I think I noted an argument supporting this view by one of the
references in a different article, where she identified herself as a
professional in sensory sciences (with an emphasis on visual, but she
gave a reasonable sounding bunch of medical jargon for why and where
we detect phase).

Comments?

Kent, the man from xanth.