christos
Supreme Member
What Is Realism In Sound Reproduction?
In this article, realism in staged music sound reproduction will usually be understood to mean the generation of a sound field realistic enough to satisfy any normal ear-brain system that it is in the same space as the performers, that this is a space that could physically exist, and that the sound sources in this space are as full bodied and as easy to locate as in real life. Realism does not necessarily equate to accuracy or perfection. Achieving realism does not mean that one must slavishly recreate the exact space of a particular recording site. For instance, a recording made in Avery Fisher Hall but reproduced as if it were in Carnegie Hall is still realistic, even if inaccurate. It is doubtful that any home reproduction system will be able to outperform a live concert in a hall the caliber of Boston's Symphony Hall, but in many cases the home experience can now exceed a live event in acoustic quality. For example, a recording of an opera made in a smallish studio, can easily be made to sound better at home, using the methods described below, than it did to most listeners at a crowded recording session. One can also argue that a home version of Symphony Hall, where one is apparently sitting tenth row center, is more involving that the live experience heard from a rear side seat in the balcony with obstructed visual and sonic view.
In a similar vein, realism does not mean perfection. If a full symphony orchestra is recorded in Carnegie Hall but played back as if it were in Carnegie Recital Hall, one may have achieved realism but certainly not perfection. Likewise, as long as localization is as effortless and as precise as in real life, the reproduced locations of discrete sound sources usually don't have to be exactly in the same positions as at the recording site to meet the standards of realism discussed here. (Virtual Reality applications, by contrast, often require extreme accuracy but realism is not a consideration.) An example of this occurs if a recording site has a stage width of 120° but is played back on a stage that seems only 90° wide. What this really means in the context of realism is that the listener has moved back in the reproduced auditorium some fifteen rows, but either stage perspective can be legitimately real. Finally, being able to localize a stage sound source in a stereo, surround sound or Ambisonics system does not guarantee that such localization will sound real. For example, a soloist reproduced entirely via one loudspeaker is easy to localize but almost never sounds real.
Reality Is In The Ear Of The Behearer
While it is always risky to make comparisons between hearing and seeing, I will live dangerously for the moment. If from birth, one were only allowed to view the world via a small black and white TV screen, one could still localize the position of objects on the video screen and could probably function quite well. But those of us with normal sight would know how drab, or I would say unrealistic, such a restricted view of the world actually was. If we now added color to our subject's video screen, the still grossly handicapped (by our standards) viewer would marvel at the previously unimaginable improvement. If we now provided stereoscopic video, our now much less handicapped viewer would wonder how he had ever functioned in the past without depth perception or how he could have regarded the earlier flat monoscopic color images as being realistic. Finally, the day would come when we removed the small video screens and for the first time our optical guinea pig was able to enjoy peripheral vision and the full resolution, contrast and brightness that the human eye is capable of and fully appreciate the miracle of unrestricted vision. The moral of all this is that only when all the visual sense parameters are provided for, can one enjoy true visual reality. At the present time there is no visual recording or display system that any human being could mistake for the real thing, but the IMAX system is a tantalizing foretaste of what might soon be possible.
One can only achieve realism if all the ear's expectations are simultaneously satisfied.
Since most of us are quite familiar with what live music in an auditorium sounds like, we can sense unreality in reproduction quite readily. But in the context of audio reproduction, the progression toward realism is similar to the visual progression above. To make reproduced music sound fully realistic, the ears, like the eyes, must be stimulated in all the ways that the ear-brain system expects. Like the visual example, when we go from mono to stereo to matrix surround to Ambisonics to multi-channel discrete, etc.(listed in order of increasing accuracy, assuming that a new multi-channel method will actually emerge that can outperform Ambisonics or as discussed below Ambiophonics) we marvel at each improvement, but since we already know what real concert halls sound like, we soon realize that something is missing. What is usually missing is completeness and sonic consistency. One can only achieve realism if all the ear's expectations are simultaneously satisfied. If we assume that we know exactly how all the mechanisms of the ear work, then we could conceivably come up with a sound recording and reproduction system that would be quite realistic. But if we take the position that we don't know all the ear's characteristics or that we don't know how much they vary from one individual to another or that we don't know the relative importance of the hearing mechanisms we do know about, then the only thing we can do, until a greater understanding dawns, is what Manfred Schroeder suggested over a quarter of a century ago, and deliver to the remote ears a realistic replica of what those same ears would have heard when and where the sound was originally generated.
Περισσοτερα εδω http://www.stereotimes.com/comm0699a.shtml
In this article, realism in staged music sound reproduction will usually be understood to mean the generation of a sound field realistic enough to satisfy any normal ear-brain system that it is in the same space as the performers, that this is a space that could physically exist, and that the sound sources in this space are as full bodied and as easy to locate as in real life. Realism does not necessarily equate to accuracy or perfection. Achieving realism does not mean that one must slavishly recreate the exact space of a particular recording site. For instance, a recording made in Avery Fisher Hall but reproduced as if it were in Carnegie Hall is still realistic, even if inaccurate. It is doubtful that any home reproduction system will be able to outperform a live concert in a hall the caliber of Boston's Symphony Hall, but in many cases the home experience can now exceed a live event in acoustic quality. For example, a recording of an opera made in a smallish studio, can easily be made to sound better at home, using the methods described below, than it did to most listeners at a crowded recording session. One can also argue that a home version of Symphony Hall, where one is apparently sitting tenth row center, is more involving that the live experience heard from a rear side seat in the balcony with obstructed visual and sonic view.
In a similar vein, realism does not mean perfection. If a full symphony orchestra is recorded in Carnegie Hall but played back as if it were in Carnegie Recital Hall, one may have achieved realism but certainly not perfection. Likewise, as long as localization is as effortless and as precise as in real life, the reproduced locations of discrete sound sources usually don't have to be exactly in the same positions as at the recording site to meet the standards of realism discussed here. (Virtual Reality applications, by contrast, often require extreme accuracy but realism is not a consideration.) An example of this occurs if a recording site has a stage width of 120° but is played back on a stage that seems only 90° wide. What this really means in the context of realism is that the listener has moved back in the reproduced auditorium some fifteen rows, but either stage perspective can be legitimately real. Finally, being able to localize a stage sound source in a stereo, surround sound or Ambisonics system does not guarantee that such localization will sound real. For example, a soloist reproduced entirely via one loudspeaker is easy to localize but almost never sounds real.
Reality Is In The Ear Of The Behearer
While it is always risky to make comparisons between hearing and seeing, I will live dangerously for the moment. If from birth, one were only allowed to view the world via a small black and white TV screen, one could still localize the position of objects on the video screen and could probably function quite well. But those of us with normal sight would know how drab, or I would say unrealistic, such a restricted view of the world actually was. If we now added color to our subject's video screen, the still grossly handicapped (by our standards) viewer would marvel at the previously unimaginable improvement. If we now provided stereoscopic video, our now much less handicapped viewer would wonder how he had ever functioned in the past without depth perception or how he could have regarded the earlier flat monoscopic color images as being realistic. Finally, the day would come when we removed the small video screens and for the first time our optical guinea pig was able to enjoy peripheral vision and the full resolution, contrast and brightness that the human eye is capable of and fully appreciate the miracle of unrestricted vision. The moral of all this is that only when all the visual sense parameters are provided for, can one enjoy true visual reality. At the present time there is no visual recording or display system that any human being could mistake for the real thing, but the IMAX system is a tantalizing foretaste of what might soon be possible.
One can only achieve realism if all the ear's expectations are simultaneously satisfied.
Since most of us are quite familiar with what live music in an auditorium sounds like, we can sense unreality in reproduction quite readily. But in the context of audio reproduction, the progression toward realism is similar to the visual progression above. To make reproduced music sound fully realistic, the ears, like the eyes, must be stimulated in all the ways that the ear-brain system expects. Like the visual example, when we go from mono to stereo to matrix surround to Ambisonics to multi-channel discrete, etc.(listed in order of increasing accuracy, assuming that a new multi-channel method will actually emerge that can outperform Ambisonics or as discussed below Ambiophonics) we marvel at each improvement, but since we already know what real concert halls sound like, we soon realize that something is missing. What is usually missing is completeness and sonic consistency. One can only achieve realism if all the ear's expectations are simultaneously satisfied. If we assume that we know exactly how all the mechanisms of the ear work, then we could conceivably come up with a sound recording and reproduction system that would be quite realistic. But if we take the position that we don't know all the ear's characteristics or that we don't know how much they vary from one individual to another or that we don't know the relative importance of the hearing mechanisms we do know about, then the only thing we can do, until a greater understanding dawns, is what Manfred Schroeder suggested over a quarter of a century ago, and deliver to the remote ears a realistic replica of what those same ears would have heard when and where the sound was originally generated.
Περισσοτερα εδω http://www.stereotimes.com/comm0699a.shtml
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