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Tetrahedral systems

Subject: Tetrahedral systems
From: Wild Sanctuary <>
Date: Tue, 15 Jun 2004 16:11:44 -0700
Yup. We mixed such a soundscape as described at a museum installation
in the late 80s, Kevin. Worked just fine with very inexpensive
speakers and a four-channel cassette playback system that kept
recycling. The illusion is quite satisfying - particularly geese
taking off from one corner of the room, flying overhead and
disappearing into the far distance behind the listener.

Bernie





>Lang,
>As long as we're setting up the ideal listening room may I dredge up my
>old idea of mounting 4 mics in a tetrahedral (pyramid shape) with 3 on
>the surface plane parallel to the earth and one pointed upward?  Then
>all sounds coming from all directions would be localized.  (An isolating
>barrier between the mics would be helpful.)  A bird flying overhead
>would really sound like it's right there in 3D.  The listening room
>might need to be an indoor pyramid with one speaker mounted directly
>overhead.  Has anyone tried this?
>
>Kevin
>
>-----Original Message-----
>From: Lang Elliott 
>Sent: Tuesday, June 15, 2004 2:28 PM
>To: 
>Subject: Re: [Nature Recordists] Re: for all you high end surround heads
>out there
>
>My only practical experience was at the Nature Sounds Society workshop
>where
>we set up a simple quad speaker arrangement in a small cabin. We did
>utilize
>blankets to reduce reflections, but the setup was very crude indeed. And
>it
>worked really well, or seemed to. At least the results were encouraging.
>My
>conclusion was that it would be fairly simple to put together a home
>quad
>setup that would work. One could certainly do it nearfield, by placing
>the
>speakers around a swivel chair, maybe six to eight feet away. The swivel
>chair would keep the listener in the sweet spot.
>
>Again, this is not for your average listener. This is for our pleasure.
>The
>only way a group could experience such immersive sound is to do it in a
>large room, with maximum speaker distance from the listener. This would
>enlarge the sweet spot considerably. A nearfield setup would have a
>small
>sweet spot, but it would certainly be large enough for an individual in
>a
>swivel chair.
>
>The sweet spot in our cabin setup seemed pretty large, meaning it was
>easy
>to find and easy to stay in it while turning in different directions.
>And
>this was a rather small cabin, maybe 12' wide by 16' long or
>thereabouts.
>
>The best listening situation no doubt would be a relatively dead room
>without reflections. That way the sense of perceived spaciousness is
>provided completely by the signals from the speakers, which I think
>should
>be rich in binaural cues (that's why I would choose a quad-binaural type
>of
>mike array design). Then the sense of landscape and geography will be
>imparted by the sound itself. You will hear what you would have heard in
>nature, or nearly so. Room reflections would degrade the experience to
>one
>degree or the other. Nonetheless, things sounded pretty darned good in
>the
>little cabin at the workshop.
>
>Right Greg? (who is Greg? He is Greg Weddig and he was at the NSS
>workshop
>and tested his own quad mike setup)
>
>
>I completely understand, Lang. I was simply recounting my experience
>with the attempt of reproducing something heard in my mind's ear from
>one environment (trans. medium) to another. As we discussed during
>your recent visit, I am still trying to do something similar to the
>illusion you're speaking about using 2 M-S systems back-to-back and
>with reversed channels (on one system) with some success - as long as
>the indoor room environment will support it - a rare situation in our
>square, parallel-surfaced environments. Therein lies one of the major
>rubs, I suspect, since to reproduce what's there in the first place
>(assuming an absolutely perfect input transducer system) would
>require a similar physiological landscape and geography, as well,
>wouldn't it?
>
>Bernie
>
>>Bernie:
>>
>>Hrmph!
>>
>>I'm trying to figure out a way that "I" or "we who are interested" can
>have
>>a rich and wonderful playback experience. For satisfying "they" in the
>  >marketplace, the best approach is to conform to a 5.1 setup.
>>
>>But realize that the technique I'm suggesting can easily be "degraded"
>into
>>5.1. There are different ways of doing this. The most obvious is to
>send two
>>neighboring channels to front right and front left, then send the other
>two
>>channels to rear right and rear left (this means that a listener could
>adopt
>>the quad setup if he wanted to). If this produces any confusion because
>>there's too many discrete signals in the rear channels, then adding a
>delay
>>on the rear channels will do magic (or so I am told), but this will
>screw up
>>the marvelous quad possibility. But who cares if we're just trying to
>>satisfy the average consumer?
>>
>>In no way does the technique I'm describing rule out 5.1 playback. But
>it
>>does rule in the possibility of a quad speaker setup and a resulting
>indoor
>>soundscape that blows 5.1 away (at least from my point of view). Thus,
>we
>>enthusiasts can format our surround for the wider audience but then
>enjoy a
>>much more immersive and accurate experience ourselves, using just four
>>identical speakers.
>>
>>I am talking here about reproducing the sound experience as it actually
>>occurs, or nearly so. True, this is a form of illusion, but it is an
>>illusion that really mirrors reality and thus is quite useful in terms
>of
>>documenting biophonies.
>>
>>Antonio Celis has a wonderful application of this kind of recording. He
>is
>>doing bird survey work down in Riverside CA, and he's experimenting
>with
>>using field recordings for the scientific analysis of choruses. He
>makes his
>>field recordings and then has trained blind listeners document what
>they
>>hear. The object is to demonstrate that such indoor listeners can
>produce an
>>accurate assessment of what really was happening in the field. By
>allowing
>>them to listen in a 360 degree soundscape, it is probable that their
>>accuracy will increase. In any event, it is quite important for survey
>work
>>that a realistic soundscape be reproduced in the indoor listening
>setup.
>>
>>Why survey birds with recordings? Well, for several reasons. One is
>that the
>>recording provides an archival documentation that can be re-analysed at
>any
>>point in time. Also, it allows the listener to rewind and listen again
>to
>>busy sections where birds are singing simultaneously from all
>directions. By
>>rewinding and then facing toward the different birds, a more accurate
>>assessment can be made. That is something that cannot be done in the
>field,
>>where it all rushes by never to be heard again.
>>
>>Antonio clearly understands the limitations of 5.1 in this respect and
>he's
>>probably the only one currently experimenting with more immersive
>>bird-oriented surround experiences that ultimately can be used for very
>>fine-tuned survey work.
>>
>>Constructed ambiences are a completely different ballgame. While they
>may
>>please many a listener and provide them with a varied soundscape
>experience,
>>they do not at all provide an accurate documentation of natural
>soundscapes
>>or biophonies.
>>
>>Apples and oranges, Bernie. Both taste good, but they're entirely
>different
>>critters.
>>
>>Lang
>>
>>
>>
>>The "indoor" acoustic problem, as I see it, Lang, is architectural
>>and practical, rather than hopefully rational. I get the strong
>>impression that in typical Western homes, the ways in which rooms and
>>furniture are generally laid out obviate simple solutions to playback
>>of the type(s) being suggested here.
>>
>>It is the same reason that four-channel discrete failed as a concept
>>during the late 60s and early 70s. It worked in Japan because the
>>room layout and spatial concepts are very different. But not in
>>Europe or N. America. Seduced early into embracing the idea, I
>>remember a jazz album Paul Beaver and I did for Warner Brothers
>>(Gandharva) - the first four-channel discrete music recording of its
>  >kind done in 1971 in Grace Cathedral in San Francisco featuring the
>>late Gerry Mulligan (bari sax), Bud Shank (tenor and flute), Howard
>>Roberts (git), Gael Laughton on 2 concert harps (at the same time),
>>Paul on 5-manual organ, and me on Moog synth. all done in spectacular
>  >surround. The disappointing fact was that no one in North America
>>could play the disk as it was intended because of the limitations
>>noted above. The older I get, the more I sense the importance of not
>>trying to replicate what happens in the wild natural in indoor
>>environments designed primarily to shut out that experience in the
>>first place. My thought for what it's worth: If ya wanna hear the
>>sound all around, then go to where it's happening and pay careful
>>attention to the spaces we've created specifically to place barriers
>>between us and it. If you're recording, create whatever illusion
>>engages your fancy, but remember Luc Ferry's axiom: "Nature is
>>beautiful when it imitates art."
>>
>>Bernie
>>
>>>Rich:
>>>
>>>I assume you're playing this back using a typical 5.1 setup, but not
>using
>>>the front center speaker. I wonder what happens to imaging if you were
>to
>>>walk and talk around your array in a big circle. Then play the
>recording
>>>back indoors and see if what you hear resembles what actually happened
>(in
>>>other words, upon playback do you sound like you're circling around
>the
>>>array?). And can you also turn and face yourself as you walk and talk,
>>>without a breakdown of the imaging?
>>>
>>>I'm looking for a miking and playback technique that reproduces as
>close as
>>>possible the actual experience; where individual soundmakers actually
>come
>>>from the directions in which they naturally occurred, and where the
>listener
>>>is free to turn in whatever direction he desires. This is what we can
>do
>>>outdoors, so why not indoors too?
>>>
>>>Lang
>>>
>>>--- In  Lang Elliott <>
>>>wrote:
>>>
>>>....
>>>
>>>>    And the Holophone design won't do this for me.
>>>
>>>Agreed it won't do it for me either.
>>>If I wanted to mic a quartet and put the mic in the center then maybe.
>>>
>>>I will just describe my personal favorite to add to the mix on this
>>>thread.
>>>
>>>Critters are often found most dense in oval shaped territories.
>>>Often where there is a critter highway between two good land areas.
>>>This is why I started playing with linear arrays.
>>>
>>>Try placement of a binaural (take your pick of sass, square barrier,
>>>million dollar man head, whatever) place that in the center or most
>>>important area you can find.  Then, place two omni mics each 25 to 50
>>>feet out to the sides from the binaural to form a line. Exact spacing
>>>is determined based on loudness of the voice of individual callers
>>>and just listening for the sweet spots.
>>>
>>>The binaural is the left and right fronts, and the omnis are the
>>>rears.
>>>The benefit is a large area of capture where the rears expand the
>>>image from the fronts, add species density to the whole recording,
>>>and no channel gets in the way with any other.
>>>
>>>Rich Peet
>>>
>>>
>>>
>>>
>>>
>>>"Microphones are not ears,
>>>Loudspeakers are not birds,
>>>A listening room is not nature."
>>>Klas Strandberg
>>>
>>>
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>>>
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>>>
>>>
>>>
>>>[Non-text portions of this message have been removed]
>>   >
>>>
>>>
>>>
>>>"Microphones are not ears,
>>>Loudspeakers are not birds,
>>>A listening room is not nature."
>>>Klas Strandberg
>>>Yahoo! Groups Links
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>>
>>[Non-text portions of this message have been removed]
>>
>>
>>
>>
>>"Microphones are not ears,
>>Loudspeakers are not birds,
>>A listening room is not nature."
>>Klas Strandberg
>>Yahoo! Groups Links
>>
>>
>>
>  >
>
>
>
>
>
>[Non-text portions of this message have been removed]
>
>
>
>
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
>


--

Wild Sanctuary, Inc.
P. O. Box 536
Glen Ellen, California  95442-0536
Tel: (707) 996-6677
Fax: (707) 996-0280
http://www.wildsanctuary.com


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