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opinions on "Sound Fields"



First of all, thanks to all who responded, you've given food for thought. I
tend to agree that "environment" is more vague (or general) than "field". A
common thread
seems to be that "field" is more specified, is artificial, and tied to a
particular 'sampling perspective', whereas "environment" is not so bounded,
nor centered on a specific perceiver or device.
So, a "sound field" could be said to be a *specific*, physical description,
which is inevitably task-specific (and therefore not automatically
generalisable).
I must admit, it was thinking of J.J.Gibson's use of the term "visual field"
(similar to the Gestaltists' use) that led me to ask after others' opinions.
I must also admit, I hadn't thought of either term referring to the entire
audible (or potentially so) output of an object, and certainly can't think
of an adequate alternative!
My particular interest is in thinking about (auditory) spatial perception in
artificial environments; I've a feeling that we generally try to make
realistic environments out of fields, and that this attempt is, by itself,
doomed to fail.
Lastly, a quote from William James:
    "Reality consists of a conscious field plus its object as felt or
    thought, plus an attitude towards the object plus a sense of self to
    whom the attitude belongs. Such is a full fact of the kind to which
    all realities whatsoever must belong. That unsharable feeling
    each one of us has of the pinch of his individual destiny as he
    privately feels it rolling out on fortune's wheel may be disparaged
    for its egotism, may be sneered at as unscientific, but is the one
    thing that fills up the measure of our concrete actuality, and any
    would be existent that should lack such a feeling would be a piece
    of reality only half made up."
I'm not sure if that sheds some light or not!

thanks again, and below is a collection of the responses.
ppl
Peter Lennox
Hardwick House
tel: (0114) 2661509
e-mail: peter@lennox01.freeserve.co.uk
or:- ppl100@york.ac.uk


Peter--

I think the term "sound field", as used in most acoustic texts, can be
summar4ized fairly directly as follows:

The sound field is the distribution of acoustic pressure and particle
velocity generated by a source (or collection of sources) in the relevant
open, partially bounded, or fully enclosed space.

If there are penetrable boundaries, the sound field may or may not include
the acoustic pressure and particle velocity existing in the boundaries (in
an enclosed environment like a room, the sound field may include that in the
room, and if relevent, that in the walls of the room and exterior to the
room). Generally, any portions of the total field that are not relevent to
the discussion at hand are usually not included.

I should point out that it is not really necessary to specify both acoustic
pressure and particle velocity. Given one, the other can be determined
completely by use of the "velocity potential" which connects the two
quantities.

There are a number of texts that may be of use, including:

"Acoustics", Beranek;
"Acoustics--an Introduction to its Physical Principles and Applications",
Pierce;
"Fundamentals of Acoustics", Kinsler, Frey, Coppens, and Sanders;
"Theoretical Acoustics", Morse and Ingard;
"Vibration and Sound", Morse.

Best, Alan Coppens

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To my mind, the terms "soundfield," "soundscape," and "sound
environment" are interchangeable.  I tend to use "soundscape" and
"soundfield" to refer to sounds we hear on playback of pre-recorded
material, and "sound environment" to refer to naturalistic
(ecological) sound sources, but I have no reason to believe this is
standardized.

Dan Levitin


==========================================
Daniel J. Levitin                                Phone: (514) 398-8263
Assistant Professor                        FAX:     (514) 398-4896
Department of Psychology
Associate Member of the Faculty of Music

Mailing Address:
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email: levitin@ego.psych.mcgill.ca
I'd be very interested too - please let me know what you hear.

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To me, a soundfield is an description (usually approximate) of the
behaviour of sound in a volume in the abstract or actual.

The term "sound environment" is more vague rather than more general. Does
it include environmental considerations such as visual cues (soundfields
don't)? Is it bound to a particular physical space (soundfields aren't)?
Does it describe how the acoustic space will react to sounds produced by
the listener (soundfields don't)?

I'd be interested in some examples from you of sound fields and sound
environments.

--Richard Furse

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Hi Peter!
Here's my definition:
soundfield, n. A region of space in which sound exerts an influence.
cf. gravityfield, forcefield. Soundfields have structure and exhibit certain
properties such as coherence.

I tend use the term "soundfield" as opposed to "sound environment"
because *very* unfortunately, "environment" (like "system") has been
so over/mis-used as to be virtually useless; just as people often use
"proof" when they really mean "postulate."

I like the term "soundfield" because it reminds me of gravity fields in
which
the field is created by the gravitational forces of proximate objects and
as you will recall from my Organised Sound paper, I think space is created
by the presence of sound ie purturbations of atmospheric pressure which
exhibit certain characteristics.

 bientot,

David.


experimental composer
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without any detailed knowledge of these terms but with experience as a
lexicographer, it sounds (!) to me as if 'sound field' refers to a
particular or localised area of the overall, more general sound
environment, an acoustic niche if you like. I'd be interested to know
what conclusions you come to...

--
duncan marshall
____________________________________________________________________

It seems to me that the term "sound field" relates to the sound source,
while "sound environment" relates to the listener. The first term is
acoustic only, while the second involves a human receiver. Or what?

Sigurd Saue
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In applied mathematics people talk about a "field" whenever a ("dependent")
scalar variable which varies as a function of one or several other
"independent" variables. If you pick your dependent variable to be sound
pressure level and  time, frequency, spatial coordinates of source
position, and so on as your independent variables, then you get a
definition of sound field which is very "inclusive", but nevertheless
"mathematically exact". That definition may be a bit broad, but I find any
further restricitions would be very arbitrary, and wouldn't gain us
anything. Does that help?

Jan

>
------------------------------------------------------
Dr. Jan Schnupp
Oxford University, Laboratory of Physiology, Parks Road, Oxford OX1 3PT,
U.K.
Tel (+44-1865) 272 513  Fax (+44-1865) 272 469

___________________________________________________________________

Purely personal opinion, but "sound field" refers to the physical
pressure velocity situation sampled at a point in a particular "sound
environment". So sound environment is a broad term referring to the sum
total of sounds being produced in a physical location, the sound field
is a technical term referring to the pressure/velocity of the sum of all
sounds measured at a point within that sound environment. Therefore the
sound environment would exist whether or not the sound field was being
measured, but the sound field only exists when that measurement has been
taken at a locus in space and time. No doubt this definition will be
shot down in flames!

Cheers Dallas.
--
Dallas Simpson

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Dear List,

One could make an argument that the answer to Peter's question about the use
of "field" in perceptual research is exactly the opposite of the one
proposed by Jan and Sigurd.

The Gestalt psychologists and other researchers in vision used the
expression "visual field" to refer to the total sensory information
available to eye of the observer, without the observer's moving.  So an
object could be "within" the viewer's visual field, at any definite moment,
or "outside" it.

The visual environment would be all the light-emitting or reflecting
surfaces surrounding the observer, whether within his visual field or not.
The use of the word "field" by the Gestaltists also implied some interaction
of the array of information with "forces" propagating as if in a field.

By analogy, one could talk of another perceptual field, the "auditory field"
that would consist of all the sounds currently affecting the listener's
ears, perhaps extended over some short time window.  Again one could talk
about sounds that were "outside the field" (e.g., too far away, too soft).
And again there would be the assumption that the sound components interacted
in perception, rather than acting independently.

By contrast the "auditory environment" would be the array of potentially
audible acoustic energy surrounding the listener.

There probably isn't any principled reason to prefer one type of terminology
over another.  The literature is not flooded with articles using a preferred
definition.  My advice to Peter would be to use any plausible definition,
but to tell his readers how he was defining the terms, and then to make sure
that his argument always respected those definitions.

Al
-------------------------------------------------
Albert S. Bregman, Emeritus Professor
Dept of Psychology, McGill University
1205 Docteur Penfield Avenue
Montreal, QC, Canada H3A 1B1

Tel:  +1 (514) 398-6103
Fax: +1 (514) 398-4896
bregman@hebb.psych.mcgill.ca
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Hi Peter,

I'd be interested to read these responses. I hope we can read them here on
the list. My own initial thoughts are that a "sound field" is centred around
a *recording* device (microphone/s), usually fixed, and the re-production of
that acoustic/spatial data (quantitative), and a "sound environment" is
human centred, around *listening* (qualitative), and usually inter-related.
We could say that all acoustic information arriving at a recording device is
a "sound field" and all acoustic information arriving at the ear is the
"sound environment". No doubt you'd want to respond to this Peter :-)

Gregg Wagstaff

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Just a thought.

In my conception of these rather woolly terms, a sound environment is the
medium through which a sound field exists.

Probably worth less than 1 old penny.

Regards, Geoff.


Geoff Sample
Northumberland
..............

www.wildsong.co.uk
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