Re: [Sursound] distance perception in virtual environments
Hello Junfeng, it's no easy task to evaluate distance perception under anechoic conditions (which obviously hardly exists). We did this during my PhD research on WFS. Have a look at our paper: Wittek, H., Kerber, S., Rumsey, F. and Theile, G. Spatial perception in Wave Field Synthesis rendered sound fields: Distance of real and virtual nearby sources Preprint #6000, AES 116th Convention, Berlin, 2004 or my thesis on my website: http://www.hauptmikrofon.de/ Good luck, best regards, Helmut Wittek -Ursprüngliche Nachricht- Von: sursound-boun...@music.vt.edu [mailto:sursound-boun...@music.vt.edu] Im Auftrag von Junfeng Li Gesendet: Sonntag, 17. April 2011 03:28 An: Surround Sound discussion group Betreff: [Sursound] distance perception in virtual environments Dear list, I am now wondering how to subjectively evaluate distance perception in virtual environments which might be synthesized using WFS or HOA (high- order ambisonics). In my experiments, the sounds were synthesized at different distances and presented to listeners for distance discrimination. However, the listener cannot easily perceive the difference in distance between these sounds. Anyone can share some ideas or experiences in distance perception experiments? or share some references on this issue? Thank you so much. Best regards, Junfeng -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20110417/6 4a7d936/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] distance perception in virtual environments
Helmut Oellers oell...@syntheticwave.de wrote: 2011/4/26 Dave Malham d...@york.ac.uk On 24/04/2011 19:11, Helmut Oellers wrote: ...modern computers are also clever. Today nothing is unaccountable if we know the formula and all variables. That's a BIG assumption - and given the essentially chaotic (in the mathematical sense) nature of the Universe, wrong. We are now pretty certain that nothing is that predictable and that that idea's basically (old) Science Fiction - we have moved from E. E. Doc Smith's Lensman universe ( where ultimately intelligent beings could predict everything because they knew the complete starting conditions and laws of the Universe) to the Discworld universe of Terry Pratchett where one flap of a Quantum Weather Butterfly's *** wings can change the course of the entire Universe (and confound even the Gods). Hello Dave, what you are describing, I would consider as the ?Heisenberg uncertainty principle?, which disclosures, as closer we look at the things, as less we can discover. Accordingly, in the quantum world the random exist, really not computable. However, in the macro world of whole air molecules, the conditions are describable. No, not the Heisenberg uncertainty principle just, as Dave stated, chaos. At times, the weather system gets itself into a chaotic state. The motion of the planets is also thought to be chaotic. These are macro. This example of the weather system gave rise to the (unsubstantiated) claim that the flap of a butterfly’s wings in Brazil can set off a tornado in Texas. (The location of the butterfly and its effects vary.) This very nice example was then purloined and mangled by Terry Prachett who introduced a spurious reference to Quantum Theory. Regards, Martin -- Martin J Leese E-mail: martin.leese stanfordalumni.org Web: http://members.tripod.com/martin_leese/ ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] distance perception in virtual environments
Actually, the butterfly flap thing is not really good either. In chaos, things do not cause other things. The system is essentially noncausal. This is a trick point. But if a system depends unstably on its initial state, it makes no real sense to say that it depends on its initial state at all in any detail. The weather has large scale stable aspects--it is almost always warmer in the summer than in the winter for example. But the details of the weather are(it is currently believed) unstable. They are not really caused by anything in any reasonable sense. This is in fact not completely detached from quantum uncertainty because if a system is unstable then it can obviously be knocked about by quantum level changes--since it can be knocked about by arbitrarily small changes of any sort. One merges into the other. Also, there is no reason at all why a quantum uncertainty cannot have macro effects, cf. Schrodinger's cat and many other examples. Time for work. More on this later(if anyone cares) Robert On Thu, 28 Apr 2011, Martin Leese wrote: Helmut Oellers oell...@syntheticwave.de wrote: 2011/4/26 Dave Malham d...@york.ac.uk On 24/04/2011 19:11, Helmut Oellers wrote: ...modern computers are also clever. Today nothing is unaccountable if we know the formula and all variables. That's a BIG assumption - and given the essentially chaotic (in the mathematical sense) nature of the Universe, wrong. We are now pretty certain that nothing is that predictable and that that idea's basically (old) Science Fiction - we have moved from E. E. Doc Smith's Lensman universe ( where ultimately intelligent beings could predict everything because they knew the complete starting conditions and laws of the Universe) to the Discworld universe of Terry Pratchett where one flap of a Quantum Weather Butterfly's *** wings can change the course of the entire Universe (and confound even the Gods). Hello Dave, what you are describing, I would consider as the ?Heisenberg uncertainty principle?, which disclosures, as closer we look at the things, as less we can discover. Accordingly, in the quantum world the random exist, really not computable. However, in the macro world of whole air molecules, the conditions are describable. No, not the Heisenberg uncertainty principle just, as Dave stated, chaos. At times, the weather system gets itself into a chaotic state. The motion of the planets is also thought to be chaotic. These are macro. This example of the weather system gave rise to the (unsubstantiated) claim that the flap of a butterfly?s wings in Brazil can set off a tornado in Texas. (The location of the butterfly and its effects vary.) This very nice example was then purloined and mangled by Terry Prachett who introduced a spurious reference to Quantum Theory. Regards, Martin -- Martin J Leese E-mail: martin.leese stanfordalumni.org Web: http://members.tripod.com/martin_leese/ ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] distance perception in virtual environments
...modern computers are also clever. Today nothing is unaccountable if we know the formula and all variables. Audio is no mysterious. The complete sonic field would be calculatable. The only problem is the huge amount of variables. In principle, yet, we are able to calculate any wave front of the source and any of her reflections in the recording room. The Wave Field Synthesis provides the approach for handling the problem. The procedure can synthesize the complete spatial distribution of all wave fronts. In principle, also all reflections become to restore correct in time, level and direction, at least in the horizontal level of the loudspeaker rows. The really disturbing component always remained, as like at all other audio playback, the additional playback room acoustics, which deliver unwanted reflections. However, at WFS we have a chance for avoiding that problem. All we need is including the playback room properties into the synthesis. By this way becomes possible, subtract the additional detours of single wave fronts in the playback room. Never conventional procedure will be able to that, because direct wave, first reflections and reverberation inseparably merge together in the transmitting channels. Thus, the playback room unavoidably remains the disturbing component in transmitting chain. No chance exists for true spatial audio by that way, thereby. And no chance exists for reproducing the source distance correctly in the traditional way. Regards Helmut www.holophony.net I think rooms are poor substitute, and very recent on evolutionary timescales, for the predictable reflections one gets in a forest. You need the simulated forest (sort of both uniform but also random )for an accurate guess of the start time. Then you delay the direct sound arrival time from there as well as decreasing its amplitude proportional to 1/t (where t is the time-of-flight from start time to arrival at the listener).. if I remember what I tried to do. If you live in a room then expect errors but the same principle applies! We can't and don't determine the direction and distance of a sound with only two ears. We use an infinite 3d array. We just don't know the precise details of the ever-changing array. It is a very clever trick that evolution has come up with! ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20110424/ca547b2f/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] distance perception in virtual environments
Hi David, you are not alone in your insigthes. Some single discrete reflections are the most important fact for estimation of source distance. There exist research from Helmut Wittek, who was proven, play the reverberation from four different directions is absolutely sufficient. We cannot use the direction of the wave fronts in the reverberation tail for determine the position of the source. Also in the recording room, the reverberation arrives from all possible directions. Another case are the first reflections. Her delay time and direction are the most important fact for approve the source position, what inclusdes its distance and the size impression of the recording room. Such single reflections causing deep comb filter effects and change the perception considerably. On the other hand, for reverberation is valid, what floyd Toole says sometimes: As more reflections esxist as less disturbing there are. ( as far as I remember well his words ). All we need for correct distance reproduction is restore some ingle reflections from her correct starting points and the correct relation between direct wave and reverberation. Regards Helmut www.holophony.net 2011/4/19 dw surso...@dwareing.plus.com Hi List, Just popped in.. It's been a while! IMO it is a combination of time-of-flight and the inverse square law, where t=0 is a virtual point in time determined by the brain as an intercept by plotting a function of the intensity of (primarily) transverse reflections against time. Fortunately it is not necessary to work out how the brain might do this. One needs to concentrate maximising the availability, and accuracy of the information that would be needed to make such a calculation possible, without making too much muddy reverb. in the process. Mono reverb does not seem to play much, or possibly any, part in this. It seems to be extracted in some way from larger ITDs and ILDs ie. transverse discrete reflections. It took me several years to work all this out, and nobody seems to have independently come to the same conclusion in the last decade or so.. so it must be wrong. At least it is free and in the public domain now! My Heli.wav on Audio and Three Dimensional Sound Links* (long gone) was a product of precisely this method of distance synthesis. Regards, David Wareing. ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20110420/273802eb/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] distance perception in virtual environments
On 17/04/2011 02:28, Junfeng Li wrote: Dear list, I am now wondering how to subjectively evaluate distance perception in virtual environments which might be synthesized using WFS or HOA (high-order ambisonics). In my experiments, the sounds were synthesized at different distances and presented to listeners for distance discrimination. However, the listener cannot easily perceive the difference in distance between these sounds. Anyone can share some ideas or experiences in distance perception experiments? or share some references on this issue? Thank you so much. Best regards, Junfeng -- next part -- An HTML attachment was scrubbed... URL:https://mail.music.vt.edu/mailman/private/sursound/attachments/20110417/64a7d936/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound Hi List, Just popped in.. It's been a while! IMO it is a combination of time-of-flight and the inverse square law, where t=0 is a virtual point in time determined by the brain as an intercept by plotting a function of the intensity of (primarily) transverse reflections against time. Fortunately it is not necessary to work out how the brain might do this. One needs to concentrate maximising the availability, and accuracy of the information that would be needed to make such a calculation possible, without making too much muddy reverb. in the process. Mono reverb does not seem to play much, or possibly any, part in this. It seems to be extracted in some way from larger ITDs and ILDs ie. transverse discrete reflections. It took me several years to work all this out, and nobody seems to have independently come to the same conclusion in the last decade or so.. so it must be wrong. At least it is free and in the public domain now! My Heli.wav on Audio and Three Dimensional Sound Links* (long gone) was a product of precisely this method of distance synthesis. Regards, David Wareing. ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] distance perception in virtual environments
Richard Lee rica...@justnet.com.au wrote: You must simulate at least 2 things. ... You have to simulate early reflections and a reverb pattern appropriate to source distance. MAG has a paper on this under Distance Panners from an idea by Peter Craven. MAG's paper is: M.A. Gerzon, The Design of Distance Panpots, Preprint 3308 of the 92nd Audio Engineering Society Convention, Vienna (1992 Mar.) (Simulating distance effects in directional reproduction.) A commercialisation of this was the TrueVerb product from Waves. Regards, Martin -- Martin J Leese E-mail: martin.leese stanfordalumni.org Web: http://members.tripod.com/martin_leese/ ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] distance perception in virtual environments
Hi, Gavin Kearney et al have presented their work on Depth perception in interactive virtual acoustic environments using higher order ambisonic soundfields at the Ambisonics'11 symposium in Paris; the article is available online at http://ambisonics10.ircam.fr/drupal/?q=proceedings/o6 Best, Markus On 17 avr. 2011, at 19:38, Dave Hunt wrote: Hi, Date: Sun, 17 Apr 2011 09:28:28 +0800 From: Junfeng Li junfeng.li.1...@gmail.com Subject: [Sursound] distance perception in virtual environments Dear list, I am now wondering how to subjectively evaluate distance perception in virtual environments which might be synthesized using WFS or HOA (high-order ambisonics). In my experiments, the sounds were synthesized at different distances and presented to listeners for distance discrimination. However, the listener cannot easily perceive the difference in distance between these sounds. Anyone can share some ideas or experiences in distance perception experiments? or share some references on this issue? Thank you so much. Best regards, Junfeng Change in amplitude with distance should be perceptible fairly easily, but on its own would just sound the same but quieter, or louder. High frequency absorption by the air is only really perceptible when the distance is fairly large, though this effect could be exaggerated for artistic purposes. The lateness of arrival of sound from distant objects is not directly perceptible unless there is something visible (e.g. lightning and thunder). Reverberation definitely gives perceptible distance effects. More distant sources are more reverberant. The amplitude of the direct signal should decrease with distance (inverse square law, or some similar law), while the amplitude of the reflected and reverberant signal would remain fairly constant or decrease less rapidly with distance than that of the direct signal. It is the ratio of direct to reverberant sound that is important. John Chowning's 1971 paper The Simulation of Moving Sound Sources is a good early consideration of how to synthesise distance. Of course the reported result will depend on the listener, who may not be used to analysing sound for these effects. Ciao, Dave ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] distance perception in virtual environments
That's an interesting question. The environment you're working in for synthesis could matter quite a bit. That is, if your working in, or simulating, an environment with little reverberation it is harder to judge distance since direct-to-reflected energy ratio is an important cue. The other important cue is timbre detail - especially high frequencies. But this requires the listener be familiar with the sound source to be able to discriminate. Try testing with spoken voice. I can't think of any research of the top of my head (especially for multi-channel environments). It is certainly well known that controlling high frequencies and direct/reflected ratio is important for distance perception in stereo mixing - but even there that's usually a relative, or comparative judgment, of one sound source appear vaguely 'behind' another. Not so much an absolute judgment that you might want for a virtual environment. jim On Sat, Apr 16, 2011 at 9:28 PM, Junfeng Li junfeng.li.1...@gmail.comwrote: Dear list, I am now wondering how to subjectively evaluate distance perception in virtual environments which might be synthesized using WFS or HOA (high-order ambisonics). In my experiments, the sounds were synthesized at different distances and presented to listeners for distance discrimination. However, the listener cannot easily perceive the difference in distance between these sounds. Anyone can share some ideas or experiences in distance perception experiments? or share some references on this issue? Thank you so much. Best regards, Junfeng -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20110417/64a7d936/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound -- Jim Moses Technical Director/Lecturer Brown University Music Department and M.E.M.E. (Multimedia and Electronic Music Experiments) -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20110417/5157390f/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] distance perception in virtual environments
For relatively nearby distance detection such as the buzzing bee or whispering or conversation (versus more distant sources such as in a concert hall), one needs to deliver interaural level differences on the order of 10 ot 20 dB with the corresponding ITD of up to 700 microseconds. (If the sources and speakers are relatively centered then we can ignore the pinna distance detection problem.) At the moment I believe only the Choueiri BACCH dummy head recording and crosstalk cancellation method can routinely deliver this magnitude of ILD over the full range of frequencies. If you are synthesizing the ILD in your virtual signals then you don't need to use a dummy head or an Ambiophone. Of course, this ILD seems to apply only for distances to sources at the sides of the head but in practice extreme XTC and thus real binaural ITD provides for proximity at all frontal angles in the horizontal plane as in everyday hearing. RACE, if carefully implemented with directional nearfield speakers, can get up to about 10 dB or more ILD and you might try this since it is easier (cheaper) than using any of the other crosstalk cancelling or WFS or HOA methods. There is no question that Ambiophonic users report enhanced depth perception when listening to ordinary music or the commercially available earphone type binaural recordings but you may want more than this for what you are doing so you should tweak the normal Ambiophonic methodology to optimize ILD capture and reproduction. Ralph Glasgal www.ambiophonics.org From: Junfeng Li junfeng.li.1...@gmail.com To: Surround Sound discussion group sursound@music.vt.edu Sent: Saturday, April 16, 2011 9:28 PM Subject: [Sursound] distance perception in virtual environments Dear list, I am now wondering how to subjectively evaluate distance perception in virtual environments which might be synthesized using WFS or HOA (high-order ambisonics). In my experiments, the sounds were synthesized at different distances and presented to listeners for distance discrimination. However, the listener cannot easily perceive the difference in distance between these sounds. Anyone can share some ideas or experiences in distance perception experiments? or share some references on this issue? Thank you so much. Best regards, Junfeng -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20110417/64a7d936/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound -- next part -- An HTML attachment was scrubbed... URL: https://mail.music.vt.edu/mailman/private/sursound/attachments/20110417/da4e9255/attachment.html ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
