opinions on "Sound Fields" (Peter Lennox )

Subject: opinions on "Sound Fields"
From:    Peter Lennox  <peter(at)LENNOX01.FREESERVE.CO.UK>
Date:    Fri, 8 Dec 2000 16:58:42 -0000

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 bounde= d, nor centered on a specific perceiver or device. So, a "sound field" could be said to be a *specific*, physical descriptio= n, 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 fie= ld" (similar to the Gestaltists' use) that led me to ask after others' opinio= ns. I must also admit, I hadn't thought of either term referring to the entir= e audible (or potentially so) output of an object, and certainly can't thin= k 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(at)lennox01.freeserve.co.uk or:- ppl100(at)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 includ= e the acoustic pressure and particle velocity existing in the boundaries (i= n 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 t= o the discussion at hand are usually not included. I should point out that it is not really necessary to specify both acoust= ic 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 -------------------------------------------------------------------------= --- ------------------------------------------ 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 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 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: McGill University Stewart Biology Building 1205 Ave. Dr. Penfield Montreal, PQ H3A 1B1 CANADA email: levitin(at)ego.psych.mcgill.ca I'd be very interested too - please let me know what you hear. ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;= ;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; 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 -------------------------------------------------------------------------= --- ------------------------------------ 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 cert= ain 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 create= d by the presence of sound ie purturbations of atmospheric pressure which exhibit certain characteristics. =E0 bientot, David. experimental composer www.avatar.com.au tel/fax: +61 2 mobile: _____________________________________________________________ 3D soundscapes - portable geodesics - mixed-media ___________________________________________________________________ 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 ****************************************************** Voxelvision AS * work: +47 73 87 36 97 Fjordgt. 56-58 * home: +47 74 85 70 67 P.O.Box 838 * fax: +47 73 87 36 99 N-7408 TRONDHEIM * email: sigurd.saue(at)voxelvision.com NORWAY * URL: http://www.voxelvision.com ****************************************************** 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 an= y 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 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D 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 momen= t, 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 interact= ion of the array of information with "forces" propagating as if in a field. By analogy, one could talk of another perceptual field, the "auditory fie= ld" 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 interac= ted 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 terminol= ogy over another. The literature is not flooded with articles using a prefer= red 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 s= ure 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(at)hebb.psych.mcgill.ca -------------------------------------------------------------------------= --- -------------------------------- Hi Peter, I'd be interested to read these responses. I hope we can read them here o= n the list. My own initial thoughts are that a "sound field" is centred aro= und 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-relate= d. 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 _________________________________________________________________________= ___ _________________________________________________________________________= ___ 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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