From: Tom MacIntyre
Subject: Re: Bullshit wins v. science
X-Newsreader: Forte Free Agent 1.92/32.570
Date: Fri, 08 Nov 2002 04:13:24 GMT
NNTP-Posting-Date: Fri, 08 Nov 2002 00:13:24 AST
On Thu, 7 Nov 2002 19:29:55 -0600, "jcurtis"
>I'm new here and just tapped in, but there is a HUGE body of literature
>(some of which I wrote) concerning how the ears localize. Lows very poorly
>but some with phase shift or time of arrival. Highs by intenisty
>differences due to head blocking.
I'm totally deaf in one ear (skull fracture in 1983), and have
practical experience in this; as well, I have worked as a sound
engineer and musician (before and after the loss), and have some basic
physics knowledge. A few observations...
I really miss the binaural hearing in many ways. An alarm clock or
cellphone, etc, under a cushion or bed, is impossible for me to find,
or nearly so. I hear a change when a switch from stereo to mono is
made, but it's a loss, not a nice spreading of the sound. Almost
everything I hear, of course, seems to come from my right side. I
cannot easily follow conversation when there is background noise,
unless I have a good view of the speaker's lips, and even then it's
tough. It is inconsistent as well; sometimes I hear something that is
almost imperceptible, and other times something quite loud is missed,
resulting in more than a few accusations of selective hearing and
hiding behind the disability. The tinnitus which haunts the dead ear
24/7 is annoying to distracting to maddening, and often seems to mask
other sounds as well, and the frequency content is inconsistent. The
one good thing...
When I was in broadcasting, I could pop a 1k test up on the console,
and move my head in such a way that the sound dropped off by 20dB or
more...silver lining to the cloud. :-)
>Mark Zenier wrote in message
>> 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
>> its head).
>> >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 firstname.lastname@example.org Washington State resident