Re: Acoustic Flow Field Generation

[Eckard Blumschein <Eckard.Blumschein@xxxxxxxxxxxxxxxxxxxxxxxxxx>]

Michael S. Gordon wrote a paper: Echolocating distance by moving and
stationary listeners
_____
Kevin Austin wrote:
No loudspeaker is "flat", and: The speaker enclosure has added colorations
_____
Peter Lennox wrote:
Loudspeakers ... imitate ... fairly well ... frequency response, dynamic
range etc., but none of their design criteria have anything to do with
spatial perception.
_____
Mikael.Fernstrom wrote:
... very different directivity.
Some mics&headphones work better for music, others better for everyday sounds.
Blind people ... could determine the size and quality of rooms they were in
and
objects in front of them quite successful.
_____
Brad Libbey wrote:
I have not yet found any research showing that localization of multiple
echoes
is a viable means of removing reverberation for complex signals.
... why in reverberant settings do recordings of loudspeakers reduce
intelligibiltiy?
_____
In addition, I would like to remind of Josef Manger who has been claiming
that design and parameters ignore important aspects of auditory perception.
In theory, he is wrong since the ear has proven phasedeaf. However, I am
not sure if this dogma is actually applicable. My knowledge of the state of
the art is rougly limited to how headwize articles describe Dolby surround,
etc. I vaguely recall: With increasing frequency something strange happens
in the shadow of the head. The sound wave travels around the head on its
surface, and this way it may reach the shadowed ear. Isn't this a
whispering gallery mode? Anyway, the illusion of spatial hearing includes a
lot of preconditions. Just a few examples:

I was told, if polarity is wrong, this does not just mean that the imagined
source is located on the wrong side but it also sounds strange. What
carries the contradicting information? Doesn't this phenomenon relate to
the questions how our two ears distinguish between top and bottom, front
and back.

I remember of a record of bird song being presented in Oldenburg 2000 in
order to demonstrate the reflection of a directed movable sound beam from
the ceiling of a room. Everybody was able to precisely locate position and
elevation of the  mirror source on the ceiling. A record of human voice was
"not available". I guess, we hear the precise position by means of a
tonotopically diversified field of temporal contrasts in the SOC. In this
case I defer to an article concerning vision which has been in discussion
on Jont's list.

Manger attributes the unwelcome localization of a single loudspeakers out
of a stereo arrangement to perception of precedence. This effect may become
audible or more audible if the onsets are exaggerated by artifacts. His
Manger transducer as well as a few even more expensive electrostatic
loudspeakers show a correct impulse response. As a result, one says they
don't have a typical sound at all.

Any coloration by reverberation, by imperfect components of sound systems,
by nonlinear distortion, by antialiasing filters, by directivity, or
whatever is much more impressive and sometimes attractive as well as
disgusting at a time, and I agree with those who argue that large rooms
have so many modes that the listener perceives the coloring effect of the
room rather than many details of its shape. In other words, energy
acoustics applies rather than ray acoustics.

Clearly, in order to check whether a sculpture isn't a picture, one may go
around.

Why does reverberation reduce intelligibility? I tend to blame misleading
distraction by coloration for that, just a slight pattern shift. Doesn't
the room also create coloration? Of course, however normally we are well
trained to recognize, interprete, and subtract these colorations. This
experience may get lost, e.g. if divers are submerged in helium. I will ask
Josef Manger for intelligibility reached with his transducer as to get an
idea to what extent avoidance of the 'reverberant' artifacts affecting the
step response could contribute to the percent correct value in case of
playing back records from an environment with spatial reverberation.

With all due defer to all,
Eckard

blumschein@et.uni-magdeburg.de
http://iesk.et.uni-magdeburg.de/~blumsche/AuditoryPerception.html

Please find there also collected responses to 'alias due to lamps' in M92
to M95.