From: firstname.lastname@example.org (Mark Zenier)
Subject: Re: Bullshit wins v. science
Date: Wed, 6 Nov 2002 20:15:10 GMT
Organization: Eskimo North www.eskimo.com (800) 246-6874
NNTP-Posting-Date: 7 Nov 2002 17:48:13 GMT
In article ,
Kevin Aylward wrote:
>"Mark Zenier" wrote in message
>> In article ,
>> Kevin Aylward wrote:
>> >This is a misconception. The ear is *absolutly* *insensitive* to
>> >A static phase shift is quite undetectable. It is a Fourier analyser.
>> Er, are you deaf in one ear? Both ears combine to be sensitive to
>> phase in some of the frequency range.
>> Take a mono signal and feed it into headphones and you'll get a
>> sound source that's small point in the center of your head. Swap the
>> wires on one ear's speaker, and the perception changes to a diffuse
>> sources outside your head, on either side.
>Ahmmm. Again, This is a misunderstanding. As I *keep* pointing out, yes
>is possible to detect phase difference by *comparison* of one signal
>with another. I have made this quite clear that adding/subtracting *two*
>signals will result in frequency response effects. It is the frequency
>spectrum effect you detect, not the phase.
I'm having a semantic quibble about the dogmatic statement you made.
The point is that "the ear" has two senses, one that percieves WHAT you
are hearing, the other WHERE the sound is coming from. I contend that
the latter uses phase, or time of arrival in the millisecond time scale.
(I don't remember a reference to humans, but I remember science media
coverage of some little pencilneck bird down in Australia (a plover
or something) that some researchers were trying to figure out how it
could get direction information from a wavelength ten times the size of
>However, this is not relevant at all to the statement that the ear is
>quite insensitive to static phase shifts. That is, take a signal. Pass
>it through a phase shifter, either constant or phase varying with
>frequency. Listen to the output *on its own*. You will simply not be
>able to hear any difference.
Try this. Get a monophonic noise source. White noise, or better
something that has a nice crackle or rustle. (Something from our
evolutionary past indicating dinner). Add in a nice 400 Hz, or
thereabouts sine wave, to add a bit of depth. Feed this into
one ear. For the other ear, feed the signal though a allpass filter
or time delay, that can be switched into the circuit or bypassed.
Put on the headphones and switch the filter in and out.
WHAT you're hearing may not change. But WHERE the sound seems to
come from sure will.
Or just try to listen to Midnight Oils "Diesel and Dust" CD on
headphones. Enough platform motion to make you seasick.
Mark Zenier email@example.com Washington State resident