height information in reproduced sound stage (Off Topic)

by Rudolf150 @, Thursday, March 29, 2007, 22:10 (3949 days ago)

Hi,

This has been puzzling me during my complete audio life. Is it possible to reproduce height information from a stereo setup? Left, right and depth information I can understand. But if you look at the symmetry of the speakers, it is very hard for me to grasp that height information can be reproduced.
Has anyone any ideas on this?

Thanks,
Rudolf

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height information in reproduced sound stage

by PeterSt. ⌂ @, Netherlands, Thursday, March 29, 2007, 22:15 (3949 days ago) @ Rudolf150

Hi Rudolf,

Many ideas here. Sadly the mods don't allow to vent ideas. Well, not from my mouth anyway. :swoon:

Officially it can't.
But officially the sound can't be behind you either (without reflections).
But it just can ...

Peter

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height information in reproduced sound stage

by kurt s @, Thursday, March 29, 2007, 23:22 (3949 days ago) @ Rudolf150

"Is it possible to reproduce height information from a stereo setup?"

I say the answer is yes, but poorly. To get real height information the sound source must provide clues to the ears that the ear needs to interpret movement in height. Those clues are subtle shifts in timing and frequency response in both channels simultaneously that make the brain interpret that sound as moving up or down as opposed to left and right.

The outer ear has a shape around it that forms a different frequency response in the top position compared to the forward position and compared to the rear position. If all is done well, then the brain might interpret the sound to be above you if with the proper timing information as well as your ear's frequency response information. How do you put such information into a pair of speakers? You must encode it in there. How are recordings done? Almost all without such encoding. So actually, sounds that do appear to move up are the result usually of an accidental effect in the recording.

Mikes do have polarized frequency responses. They change with angles reaching them. If mike(s) are made and positioned to slightly encode the sound an ear would hear with such movement in height, to a rather crude fidelity to that effect, then it can project an illusion of height information in the playback, just like stereo is mainly a left-right illusion.

So again the answer I have is: Yes, some crude form of height info can be in there, but no, it is not natural nor intentional in two-channel, two-point-source recordings. And yes, you do hear it sometimes. And some speakers are much more adept at presenting such slight information clues. The best speaker I ever owned that did this effect was my Avalon Eclipses when I had those. Then I swore all recordings had height. But, alas, that was mostly illusion, and not "real". Does "sort of" make a good answer here?


Kurt

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height information in reproduced sound stage

by MikeH @, Friday, March 30, 2007, 00:57 (3948 days ago) @ Rudolf150

Read this:
http://www.audiocybernetics.com/VA.html

I have listened to a CD where this works with headphones.
It was called cyb****** (which was mostly heavy breathing and associated sounds, you get the idea). Most disconcerting hearing someone speak from close behind your head when there is a chair there. Spooky.
I have a Gravis Ultrasound sound card in my old 486PC that had the ability to generate virtual audio such as this into headphones, very good for first person games that supported it.

On my friend's singulars with AER drivers I listened to Comfortably numb, performed by the London Philharmonic (from Us And Them: Symphonic Pink Floyd)
and the horn section was definitely about 15 degrees above the horizontal on the right. I am getting goose bumps again remembering it.

I do not know where they usually place the brass section in an orchestra. Is this where they really are?

(*** is the technical name for the bit at the end.... )

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height information in reproduced sound stage

by Giovanni, Ravenna, Friday, March 30, 2007, 01:01 (3948 days ago) @ Rudolf150

There is an experiment by Chesky: Best of Chesky Jazz and More Audiophile Tests, Vol. 2", track Britten - Festival Te Deum - Westminster Choir.
Only one microphone placed on top of the choir, hanging in free space at ten meters height with no reflecting surfaces.

We could expect to hear the choir under our feet, when listening, but it is not the case. You'll hear the choir just in front of you with more depth.

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height information in reproduced sound stage

by GC, Friday, March 30, 2007, 07:58 (3948 days ago) @ Giovanni
edited by GC, Friday, March 30, 2007, 08:07

Hmmmm

One could think that we just lay our speakers flat on the floor and we levitating above them we should recognice an orchestra under us?

But we as listeners will always be hehind the mic, not as the musicians who will be in front of it.

And what is behind the mic in the end? The speakers. And we are in front of those...mostly.

So back to listening height (and here I think Kurt comes close):

Mics sees the whole recording room/hall. Some mics are directive, some omni directional. Some points this way or that way. They are even placed at different coordinates, just GPS them. You will see.
Some mics aGCulls each others if out of phase, some not. All mics hears what the others hears, but at different distances reflecting different amplitudes then.
They all hear the the instruments, the room, each other in a chaos like turmoil.
Now even a Proprious or an Opus 3 recording with their single stereo mic set-up shows the same, far less chaotic though.
There are many ways to Rome as we say.

But for all recordings (except studio direct plug-in recordings) we hear the size of the room and the coordinates of the musicians in the air print in front of our speakers. Hence height, width, depth etc.

Don't we?

GC


In a period of my life I enjoyed to be the sound guy at the mixer at rock concerts. Handeling up to 50 mics at the stage in worse cases.
Blood, Sweat and Tears I can tell you.
Being a drummer for more than 15 years I had trouble enough with my 10 mics and my local mixer there at stage.
Why does most rock mucisians ends up as wrackages, nut-cases and pure :teasing: ???
The mic stuff.....

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height information in reproduced sound stage

by Rudolf150 @, Friday, March 30, 2007, 22:57 (3948 days ago) @ GC

Thanks guys for your remarks.

It is clear for me - I am listening to a lot of Rock music - that I shouldn't expect any usefull height information; especially when for example the drums are recorded with many separate microphones.

What strikes me as well, that on my Orpheans the recorded sound is reproduced so accurately, that the size of the voice(mouth) is much larger than the other instruments.

In the past, sound stage was for me the key to get a realistic sound experience. Dynamics was less important. But with Bert's horns, the dynamics have become the key for me to get the be-there feeling.

Thinking about the particular shape of the ear to decode height information; maybe the technicians should put some earshape shields around their microphones.

I think it is best to dig out my 60's classical recordings; where they used only 2 microphones and a tape recorder.

Rudolf

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How to record height information?

by MikeH @, Saturday, March 31, 2007, 03:24 (3947 days ago) @ Rudolf150

From memory the cd I mentioned earlier was recorded this way. They not only used fake ears - they made a whole head and the actors spoke around it.
It is a shame about the content of the recording. Sitting on a beach, walking through a forest, a summer thunderstorm, walking in the snow, these are the (non musical) things I would like to hear.

You have two sensors, you can determine amplitude, frequency and phase between them, how is the height determined from this? I would expect three sampling points in a triangle to determine the source of a sound in three dimensions. Perhaps it is something to do with the shape of our head and the way the sound changes as it goes "around the corner" to the ear that is further from the sound source.

It would be interesting to experiment with a dummy head with ears and two microphones inside. Playback would be more convincing to the brain with in-ear monitors. Would one fake head work for all people or would you need a selection of shapes for different people?

Any Audio Engineers out there who can assist?

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How to record height information?

by GC, Saturday, March 31, 2007, 09:18 (3947 days ago) @ MikeH
edited by GC, Saturday, March 31, 2007, 10:26

Hi Mike

Any Audio Engineers out there who can assist?

I'm not an Audio Engineer and I am of no assistance to many, but Mike, I have something to add.

From memory the cd I mentioned earlier was recorded this way. They not only
used fake ears - they made a whole head and the actors spoke around it.
It is a shame about the content of the recording. Sitting on a beach,
walking through a forest, a summer thunderstorm, walking in the snow,
these are the (non musical) things I would like to hear.

Yeah...In Germany they called those recordings "Kunstkopf" which to my best knowledge could be translated to "artificial head" with mic's s c r e w e d directly into the poor head and placed where you normaly find the tympanies. I remember, I heard it even, but those recordings were meant for playback via a head set, right? Not real loudspeakers.
Once I heard a Kunstkopf recording with head sets clamped onto my not that well looking head, someone opened a rear door in a room with me sitting right in the middle of it. I heard the person walk towards me, scarry realistic, and that person whispered something into my left ear, caNot remember what, with such a soundpressure that made me levitate 1 meter above my chair of the shock i got.
I took me an hour to get rid of the addrenalin that whisper had generated.
Beleive me, I could have knocked that person down but failed to, as it was all an illusion despite the realism.

It would be interesting to experiment with a dummy head with ears and two
microphones inside. Playback would be more convincing to the brain with
in-ear monitors. Would one fake head work for all people or would you
need a selection of shapes for different people?

If you took the recording I mentioned above and played it back through the normal loudspeakers: Nothing special about that. No 3-D experience to find here. On the contrary it was flat, boring and indifferent.

Any Audio Engineers out there who can assist?

Maybe there is.....


GC

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height information in reproduced sound stage

by GC, Saturday, March 31, 2007, 08:58 (3947 days ago) @ Rudolf150
edited by GC, Sunday, April 01, 2007, 06:54

Hi Rudolf

What strikes me as well, that on my Orpheans the recorded sound is
reproduced so accurately, that the size of the voice(mouth) is much larger
than the other instruments.


It is mayby not so strange you hear a rock singer or what ever studio recorded voice to be "bigger" than in reallity or for that sake bigger than the whole drumset it self.

Think this little mic with a sensor (actally a loudspeaker it is) of 0,5 cm2 as an example, is stuck half into the mouth of the singer, as they per definition do that very often (grrrrr), that that voice or throat giving the sound preassure to the sensor, the mic, is many times bigger than the mic.

What do you hear then? BIG MOUTH. The mic sees the open mouth of the singer as a complete concert hall. :wink:
Should the listener be a dentist, he would jump directly into the soundstage to look for teeths to repair, but ending up smashing his head directly into the wall behind his speakers :grazy:
That is the concequenses having speakers like yours Rudolf.

The same with macro photogaphy, bigger than reallity, or a worser case: A microscope. Very very BIG REALITY.

GC the Big Mouth :shout:

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