[Gary Eickmeier]

Dick Pierce wrote:
Gary Eickmeier wrote:

Dick Pierce said in his response on 4/4/2013 at 7:27PM to AE's
previous thread:

"The fact is that the HRTF of the original sound field is
eliminate from the listening chain is precisely the problem."

Which, of course and as usual, you completely utterly
misunderstood. I would please implore you once again to
not assume that when you are confused, you immediately
assume that it's because the other person is confused.

The HRTF (do you even know what that means?) is eliminated
for a variety of reasons. Most especially in the confused
and inconsistent misrepresentations you've proferred, since
the soundfields presented by the instrument and ANY
recreation of the soundfields by ANY existing stereo
recording and playback technique are VASTLY different
(despite your unsupported claims about what your 901-
based speaker system is capable of doing), the HRTF-
processed result of that original soundfiels and that
of the reproduced soundfield must, be necessitty, be
vastly different. The fact that it work at all, as stated
by Audio_Empire and many others, is far more a testimony
to the flexibility and adaptability of the human auditory
system in being able to synthesize the resultant emotive
results, than it is to any alledged physical or technical
properties.

Again I say, HRTF has nothing to do with the stereophonic system. Your
problem with its being eliminated in the process, or the two HRTFs being
VASTLY different, show a confusion between stereophonic and binaural. HRTF
means Head Related Transfer Function. It has to do with a head-related
system, not a field type system.

snip


No, once again, Mr. Eickmeier is confused about what
Mr. Pierce said. Please stop blaming him for your confusion.

Mr. Pierce,

I started this whole new thread because of your astonishing statements in
the previous thread, in the post already quoted, that:

"ALL directional information iis lost in any single microphone.
The output of the microphone is a simply two-dimensional record
of instantaneous pressure or velocity amplitude vs time. That's
it. There is no information in that electrical signal as to where
the sound that caused it came from. None.

"As I said, even in a directional microphone, that information is
irretrievably lost. Say a directional microphone is down 20 db
120 degrees relative to the principle axis. There's nothing in
the resulting electrical stream that unambiguously (or even
vaguely) provides a clue as to whether that signal was due to
an 80 dB SPL sound on the principal axis or a 100 dB SPL sound
120 degrees off axis.

"And when you start to talk about recording in a complex sound
field, the electrical output has NO indication AT ALL whether
a direct sound came from there, while the reverberent sound
came form over there.

"Now, take a stereo pair. The situation is really not any better
It is geometrically impossible to disambiguate, for example, by
any property in the elctrical signals, whether a source of a sound
is anywhere on a circle whose center is defined by the line between
the two microphones and whose plane is at right angles to that
circle. Two omnis some distance apart will generate the SAME
electrical signals whether the source is 20 feet ahead, 20 feet
above, 20 feet behind or anywhere else on the circle. The same is
true of any other mike position. The only position that can be
unambiguously recorded is somewhere EXACTLY in between the two,
which is arguably not very useful."


But anyway, I think that the main difference between the live and the
playback is an acoustic one, not necessarily that some info gets lost
during
recording.

"Uh, sorry, but it is the 3-dimensional aspect of the original
acoustical field that is provably lost.

"The fact is that the HRTF of the original sound field is
eliminate from the listening chain is precisely the problem."

And further down:

"The reason carefully done (and VERY inconvenient) binaural works
is because it works VERY hard to try to preserve as much of the
utility of the listener's HRTF as possible."

And so what we have here is a fuzzy confusion between stereophonic and
binaural, once again thinking that the idea is to encode signals that when
they enter the ears will decode all incident angles that were recorded and
fool the listener into hearing the original space.

What I have been hammering at is that the stereophonic system does not work
by recording and reproducing ear signals, but rather by recording and
reproducing sound fields in rooms. Pierce says that the reason that stereo
doesn't work all that well is because almost all directional information is
lost and can never be resurrected again. I point out that we are not playing
the recorded channels into our ears, we are playing them on speakers
arranged where we want the sound to come from, in our playback space. Big
difference.

Spot evaluation: Record a single instrument with a single microphone. Put a
loudspeaker in your listening room in a position that is geometrically
similar to where the source was in the original room. Now NAIL IT DOWN SO IT
CAN'T MOVE. Now play the sound that you recorded. Can you tell where the
instrument is? Did the recording contain any information about where it was
originally? Did the recording have any HRTF in it? Head shadowing? Anything
to do with the human hearing mechanism?

Now make a stereo recording, maybe three instruments placed left, center,
and right. Play the recording on speakers that you have arranged in front of
you in positions that are geometrically similar to the original. Even in a
two channel recording, can you tell where the instruments are? Left, center,
and right? Is there any ambiguity about it, even though the stereo pair
could not tell which of 360 possible planes those sounds came from? So how
did you choose to make the sound come from right there and there?

I will leave the spatial reverberance part for another post, but I just want
to communicate with you for the first time the kind of difference I am
talking about. Most of us grew up in audio thinking that stereo was a vague
attempt to fool the ears into hearing another acoustic space, the one in
which the microphones were placed, by putting two channels of information
into our ears. And so if it didn't work quite like we expected, we figured
that there must be some fault in the signal path and so the search was on
for greater and greater accuracy in our microphones, electronics, recording
media, and speakers, or, as you have expressed that sufficient information
was never recorded in the first place, so it cannot work as expected.

My contribution is that you are studying the elephant from the wrong end.
The Holy Grail lies not in signals, paths, sufficient information, accuracy,
none of that. The answer lies in studying the problem of reconstructing the
recorded information as sound fields within your room - direct, early
reflected, and reverberant. If you understand the structure of this "thing"
that we are trying to rebuild within our space, you will have a much better
chance at success.

Gary Eickmeier