advertisement


What exactly is "imaging" ?

Will due respect to Tuga, if that's his argument, he isn't making it clear in his insistent reliance on the loudspeaker's dispersion characteristics, for his view that it simply isn't possible. If anybody is talking at cross-purposes, I'm not sure it is those of us who observe that we can perceive height in an image, just as we can perceive depth and width. They are part of the illusion, whether they are specifically encoded as such in the signal is somewhat moot. One of the basic requirements for media is that they enable the 'willing suspension of disbelief' - ie I know there isn't a symphony orchestra in my living room, but I'm over it. I'm content for my brain to do what it does with what it receives, and perceive the result.

I am also content for my brain to do what it does with what it receives, and perceive the result.
No one is questioning what each one of us perceives, nor our listening experiences.

Stereo is a mechanism to generate one illusion: that of placing phantom images on or between the speakers. All the rest is our imagination at work.
And here's nothing bad or wrong with that. We have all had our live experiences and that influences our perception.

Also let's not forget that because 2-channel stereo over speakers was conceived to generate an illusion the auditory location capabilities don't work in the same way as with a live source.


People get so upset, it's almost as if I said Santa doesn't exist fGs...
 
When you are watching Lawrence of Arabia on your TV you know that Laurence is a long way away in the desert on his camel, and he is riding towards you, and you could probably make a fair estimate of his distance. So in one sense, your TV "does depth" in that it can convey some of the perceptual cues for depth and distance. But the image is always only a few feet away from you, your eyes don't change focus. So the perception of depth on your TV isn't veridical. Similarly with hifi. You might get an image in your room of a choir in a cathedral, you can sense the space by the reverb, but there's no way for a recording engineer to move a sound front to back or up or down. If there was, he could get the sound out of your head when listening on headphones. Good way to make some judgments is to play mono pink noise. Where do you hear the sound? How well defined is it? Should be pretty narrow horizontally. But vertically? What might be being perceived as height could just be uncertainty.
 
Will due respect to Tuga, if that's his argument, he isn't making it clear in his insistent reliance on the loudspeaker's dispersion characteristics, for his view that it simply isn't possible. If anybody is talking at cross-purposes, I'm not sure it is those of us who observe that we can perceive height in an image, just as we can perceive depth and width. They are part of the illusion, whether they are specifically encoded as such in the signal is somewhat moot. One of the basic requirements for media is that they enable the 'willing suspension of disbelief' - ie I know there isn't a symphony orchestra in my living room, but I'm over it. I'm content for my brain to do what it does with what it receives, and perceive the result.
Sure, stereo works quite well for orchestras. But imagine a situation where it might matter whether positional height informaton was correctly encoded. Say the offstage orchestra in Mahler 2. You would know it was offstage and whether it was left or right, but offstage in the gallery, not really. stero cannot convey this height information in the way it can convey left right and (to some extent) distance.

Of course everyone enjoys what they enjoy. The problem is that it gets muddled if one is discussing the characteristics of kit (does it image- what does that mean?). What can and what cannot be encoded and decoded has a bearing on whether the illusion depends or thrives on accurate or inaccurate reproduction.
 
I disagree.

This argument isn't because you said you don't perceive height.

It's because you told us we can't perceive height.

You are correct. Perception implies senses. So I did say that you can't perceive height, that you imagine it. But what I wanted to say was that I don't doubt your experience, only that the height perception is not coming from stereophony but from your mind.
 
I stand by my statment that this is an obvious case of talking at cross purposes and depnds on an ambiguity in the meaning of the word "perceive" as between "experience" and "correctly decode" .
 
When you are watching Lawrence of Arabia on your TV you know that Laurence is a long way away in the desert on his camel, and he is riding towards you, and you could probably make a fair estimate of his distance. So in one sense, your TV "does depth" in that it can convey some of the perceptual cues for depth and distance. But the image is always only a few feet away from you, your eyes don't change focus. So the perception of depth on your TV isn't veridical. Similarly with hifi. You might get an image in your room of a choir in a cathedral, you can sense the space by the reverb, but there's no way for a recording engineer to move a sound front to back or up or down. If there was, he could get the sound out of your head when listening on headphones. Good way to make some judgments is to play mono pink noise. Where do you hear the sound? How well defined is it? Should be pretty narrow horizontally. But vertically? What might be being perceived as height could just be uncertainty.

When there are two instrument phantom images in the soundstage one can sound more distanced due mainly to level differences but also the amount of reverb, mechanical noise detail, high frequency roll off, delay...
The soundstage in most studio recordings is fabricated. Instruments are close-mic'ed in mono, pan-potted left/right/centre and then effects are added to give an impression of space and layering.
With minimally mic'ed (reasonably distant) real stereo the instrument sound will interact with the room, their relative position in respect to the microfones will be roughly distributed between the two speakers, and the room sound (reflections, reverb) will add the spatial cues and the sense of distance.
 
I should have been there, George, and on Friday to the first night, but I got pinged just as I was about to set off on Friday.
It did sound pretty good on R3.

Argh! That's a booger! :-/ I stopped going to Proms because I'd moved to Scotland! Bit further now to travel than when I could hop on the Central Line! Thank heavens for R3 and the iplayer. Been listening to this year's first night again on headphones this morning. In stereo. No sign of 'height' though. :)

That said, the 'binaural/headphone' mixes they tried a couple of years ago I thought sounded worse on *headphones* as well as speakers than their standard balance.
 
I stand by my statment that this is an obvious case of talking at cross purposes and depnds on an ambiguity in the meaning of the word "perceive" as between "experience" and "correctly decode" .
Re: what I quoted from Linkwitz earlier. Paraphrase, our hearing systems are extremely good at locating the 3D position of sound sources in the presence of other objects (e.g. the ground, walls etc.)

Putting speakers in a room, our aim is to fool the brain exactly in the area it's phenomenally good at. We DON'T want our brains to locate the real sound source(s) at all. We want the brain to perceive phantom sound sources.

Linkwitz argued that it's possible to achieve it in a room, by working with reflected sound, rather than against it, and having an even frequency response at every angle off-axis. Then the brain stops perceiving the speakers and even the surfaces in the room, thereby revealing the recording.

If you're saying the perception of the original acoustic will be distorted, degraded and reduced with a non-binaural/HRTF set up, I agree. However, you're saying no height information can be encoded at all because there are just two sound sources, which I think is a misunderstanding, since binaural can encode 3D volumes with two sound sources. What you're really arguing about is the absolute necessity of HRTF/pinnae processing so without this being handled, 3D information is completely absent - and I don't see that as necessarily and absolutely true. I don't see why some information can't be present (I've repeatedly said that it might not be technically accurate, just that something is present).
 
It feels as though I need to point out ... that real ear drums don't capture real 3D data. They capture two channel audio. All the 3D stuff comes from the convoluted intrepretation in the brain.

I think you're suffering from a lack of imagination! Humour intended.
 
Re: what I quoted from Linkwitz earlier. Paraphrase, our hearing systems are extremely good at locating the 3D position of sound sources in the presence of other objects (e.g. the ground, walls etc.)

That is correct but only for live sound sources, not for a stereo recording over two speakers. And as per the research paper mentioned earlier our ability to descriminate location on the vertical plane is poor (perhaps because our ears are located side-by-side horizontaly?)

Stereo is a trick.
 
I pity folk who only enjoy a 2D washing line stereo effect, one of my favourite things about Tannoy DC's is they image in front and behind the plane of the speakers, advantages of concentric point source and horn directivity. It's worth remembering the stereo effect is reproducing a construct only, phantom images aren't point sources between your speakers.
 
And as per the research paper mentioned earlier our ability to descriminate location on the vertical plane is poor (perhaps because our ears are located side-by-side horizontaly?)
.
When a plane flies over, I look up to the source of the sound. If my wife calls to me from an upstairs window, I look up to where her voice comes from.

Our eyes are located side by side horizontally, too, but I can see birds flying overhead. I think your conjecture as to the reason is unconvincing.
 
I pity folk who only enjoy a 2D washing line stereo effect, one of my favourite things about Tannoy DC's is they image in front and behind the plane of the speakers, advantages of concentric point source and horn directivity. It's worth remembering the stereo effect is reproducing a construct only, phantom images aren't point sources between your speakers.

The multiple layers are not the result of 2-channel stereo reproduction, or exclusive to your Tannoys. They are complementary ingredients bundled with the stereo effect which is the generation of a phantom sound source where there is none.
 
Sorry, what?
I genuinely don’t understand your point here. We know the stereo image is the generation of a phantom sound source, so why is it that this ‘complimentary ingredient’ (which I always thought was the intended effect, not some incidental by-product) can conjure up depth, but not height?
 
When a plane flies over, I look up to the source of the sound. If my wife calls to me from an upstairs window, I look up to where her voice comes from.

Our eyes are located side by side horizontally, too, but I can see birds flying overhead. I think your conjecture as to the reason is unconvincing.

Our hearing determines location through differences in amplitude (above 1.5kHz according to the JMLC piece), phase (below 1.5kHz) and timing. If a sound is coming from the left then it will sound louder and closer to the left ear with a difference in phase.
Since the ears are located horizontally to the sides of our head, it is perhaps natural that our resolution is higher on the horizontal plane; but that is just my conjecture.

But you are missing the point that stereo does not provide height or vertical location info...
 
The multiple layers are not the result of 2-channel stereo reproduction, or exclusive to your Tannoys. They are complementary ingredients bundled with the stereo effect which is the generation of a phantom sound source where there is none.

Perhaps you should consider actually reading the links you post just now and again.
Point source coherence and controlled directivity has a significant bearing on stereo perception/reproduction/construction of stable phantom images.
 
Sorry, what?
I genuinely don’t understand your point here. We know the stereo image is the generation of a phantom sound source, so why is it that this ‘complimentary ingredient’ (which I always thought was the intended effect, not some incidental by-product) can conjure up depth, but not height?

Depth is not the result of stereo. It is borne out of differences in level, reverb, high frequency roll-off, detail... You can get a sense of depth with a mono recording.
 


advertisement


Back
Top