Re: [Sursound] Sursound Digest, Vol 164, Issue 1
40-3751464 <http://decoy.iki.fi/front+358-40-3751464>, 025E D175 > ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 > > -- > > Message: 9 > Date: Wed, 6 Apr 2022 15:58:14 +0200 > From: Fons Adriaensen > To: sursound@music.vt.edu > Subject: Re: [Sursound] Reynolds mics > Message-ID: > <20220406135814.ghgbphvitfbh4...@mail1.linuxaudio.cyso.net> > Content-Type: text/plain; charset=us-ascii > > On Wed, Apr 06, 2022 at 04:13:57PM +0300, Sampo Syreeni wrote: > > > With near field sources, the outwards radiating field from a point source > > is reactive at each point. Pressure and velocity are *not* in phase, > > Even a pantophonic mic will pick that up that phase difference. > > > the vector describing energy transfer (in EM I think the Poynting vector) > > is *not* in the plane, but outwards from the source, all round. > > Which means that whatever you try to describe here is NOT a vector. > > The velocity vector will be in the horizontal plane, and is represented > correctly by X,Y. It has no Z component. > > > So what happens is that while the > > pressure field is fully symmetric in the horizontal plane, there still > has > > to be a Z component in order to recreate the field to full first order. > > Not for it to be correct for a listener in the same horizontal plane > as the speakers. Of course if the listener moves up or down the > sound field he/she senses will be incorrect. What do you expect ? > > > ...and that's precisely why pantophony is an idea born dead. We don't > have > > infinite vertical line sources, nor microphone arrays which mimic their > > directional patterns. The only thing we really have is 3D mic arrays and > 3D > > rigs. > > Indeed. But we also have situations in which most sources are in the > horizontal > plane or close to it, and as listeners we tend to stay on the ground and > not fly > around. > > Ciao, > > -- > FA > > > > -- > > Subject: Digest Footer > > ___ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound > > WHEN REPLYING EDIT THE SUBJECT LINE > > ALSO EDIT THE MESSAGE BODY > > > -- > > End of Sursound Digest, Vol 164, Issue 1 > > -- next part -- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20220406/deb736ff/attachment.htm> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
Re: [Sursound] Reynolds mics
On Wed, Apr 06, 2022 at 04:13:57PM +0300, Sampo Syreeni wrote: > With near field sources, the outwards radiating field from a point source > is reactive at each point. Pressure and velocity are *not* in phase, Even a pantophonic mic will pick that up that phase difference. > the vector describing energy transfer (in EM I think the Poynting vector) > is *not* in the plane, but outwards from the source, all round. Which means that whatever you try to describe here is NOT a vector. The velocity vector will be in the horizontal plane, and is represented correctly by X,Y. It has no Z component. > So what happens is that while the > pressure field is fully symmetric in the horizontal plane, there still has > to be a Z component in order to recreate the field to full first order. Not for it to be correct for a listener in the same horizontal plane as the speakers. Of course if the listener moves up or down the sound field he/she senses will be incorrect. What do you expect ? > ...and that's precisely why pantophony is an idea born dead. We don't have > infinite vertical line sources, nor microphone arrays which mimic their > directional patterns. The only thing we really have is 3D mic arrays and 3D > rigs. Indeed. But we also have situations in which most sources are in the horizontal plane or close to it, and as listeners we tend to stay on the ground and not fly around. Ciao, -- FA ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
Re: [Sursound] Reynolds mics
On 2022-04-06, Jack Reynolds wrote: I am here if there’s anything you want to know. Pricing, for starters, of course. :) My marketing approach so far has been word of mouth really. Appears to be working if you reach the list, and even someone like me. I have been developing the designs with much field testing help from Axel and intended the mics to be as quiet and clean sounding as possible and also to be very difficult to break while camped out in the jungle. Waterproof Lemo connectors and 3D printed nylon makes for a much more robust product than the soundfields. Have you been able to maintain the constant directional patterns, the high spatial aliasing limit, and the low noise floor of, say at best, SoundField V? What would you say the tradeoffs are for ruggedness, if any? They are based on the classic tetrahedron of cardioids and there’s not much more going on that. No sense in reinventing the wheel. But say again, which capsules do you use, and how do you support them, e.g. to insulate them from rattle and undue offsets? I mean, SoundFields are notorious for being fickle beasts. Bang them once against a corner of a table, and they need to be sent back to factory for a recalibration. You already said you take precautions, but how robust are they recording-wise? Have you measured? -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3751464, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
Re: [Sursound] Reynolds mics
On 2022-04-06, Fons Adriaensen wrote: I ask because theory-wise pantophonic and periphonic soundfields shouldn't be captured the same way, There is no such thing as a 'pantophonic sound field'. We don't live in Flatland. All microphones operate in 3D space. Some more than others. Interferometric boom mics try to operate in 1D land. You know, the ones which attenuate everything off-axis. The ideal pantophonic mic array does the same in 2D. It cuts off everything above horizon, sharply. Then the ideal pantophonic array reproduces cylindrical waves, matched. That's the only way the recording and reproduction conditions ever truly match. Faller's math showed that on blackboard, and the NFC-HOA work made it even clearer, if between the lines. The way *I* interpret the mess is that pantophony is a mirage; there can be only periphony within the ambisonic framework. We might argue about its order, or about how truly regular the capture and reproduction rigs need to really be, but in the end, the spherical harmonical framework underlying ambisonic just doesn't pan out except in full 3D. Unless you mean a sound field with all sources in the horizontal plane of the mic. Then it is just a subset of a 3D sound field, and a conventional AMB mic will capture it correctly. Actually it will not. It's easy to fall prey to the idea of planar symmetry, but the 3D soundfield doesn't behave like that. For infinitely far-away sources in the horizontal plane the symmetry idea holds, but only because such sources constitute planewaves when they hit the mic. Any closer sources even in the horizontal plane are near-field, and constitute a near-field component even in the third dimension. Recreating them to first order calls for Z as well. And if you cut out Z...we're back to Christoff's skeptical analysis of the system: the apparent amplitude of a horizontal source takes on a 1/r term within the reproduction rig, because some of the sound energy is leaking off the plane. The effect was analysed in WFS work, earlier. In there they used synthesized point sources and -- planar array that they had -- actually compensated actually for the term in software. Obviously nothing like that can be done in whole ambisonic soundfields. nor do they represent even the same encoding system. How does a sound field 'represent an encoding system' ? Your statement may be grammatically correct but it has no meaning. Sorry, I'm being vague as usual. The exact statement would be that pantophony is the theory of cylindrically symmetrical solutions to the wave equation, whereas periphony concerns itself with spherically symmetrical ones. The continuous symmetry group respected by the former is that of the one-sphere by a line, and the one respected by the second is that of the two-sphere. By well known topological reasoning, you cannot continuously, much less differentiably or linearly, embed the latter into the former, since it's of lower dimension. Neither can you work around the problem using any linear representation, as would be the case with circular/cylindrical harmonics and spherical harmonics. Working down from that idea, there can *be* *no* consistent definition of what a sound source off the horizontal plane means in pantophony. There's just no way to define it without having it vanish somewhere, or suddenly flip sign. And since we know you need planewaves of all directions in order to decompose any monopole... You might think you can forget about such behavior, but in the sense of the enveloping wave equation you actually cannot: every nearby point source in the horizontal plane requires a Z-wise component. (More on that later.) It might not be easy to see, because we're used to dealing with pointwise pressure fields only; the acoustical equation instead of the full wave equation. But then only in the case of infinitely far off sources can we assume that pressure and velocity are in phase, in the plane of symmetry. That is the far field/plane wave assumption. With near field sources, the outwards radiating field from a point source is reactive at each point. Pressure and velocity are *not* in phase, and the vector describing energy transfer (in EM I think the Poynting vector) is *not* in the plane, but outwards from the source, all round. So what happens is that while the pressure field is fully symmetric in the horizontal plane, there still has to be a Z component in order to recreate the field to full first order. You can't capture that with a periphonic array, nor can you recreate it using a periphonic rig. The only way periphony can work is by approximating infinitely far off sources i.e. planewaves. There pantophony can work, and that's how it was analyzed by Gerzon, no less. But if you want to approximate near fields -- any fully general fields -- you run into a topological singularity (pretty much the hairy ball theorem): there's just no way to map
Re: [Sursound] Antw: Re: [opus] Antw: [EXT] Opus merging streams
On 2022-04-06, Ulrich Windl wrote: I cannot for the life of me understand why Atmos exists. Except for I don't know the theory behind, but I guess they want a format open to future sound designs (i.e.: how many and where to place speakers). Third order ambisonic is already nigh correct for a central, static listener. Especially when augmented with dynamic decoding for specular sources, akin to the higher order extensions of DirAC. It really does not *need* hundreds of separate parametric sources. It's just a good enough description of the central soundfield, taken from any angle. If parallax was involved, such as in games where you don't stand still, I could understand the point. But as far as I understand it, neither Atmos nor AC-4 support anything of the kind. So where's the point? The selling point is adaptation to different speaker layouts, but high enough order ambisonic can do that already, 3rd order is well enough for regular speaker layouts, and no irregular layout is going to work even for re-rendered specular sources. That's just basic math: irregular enough meshes don't admit stable quadrature. Plus in the meanwhile, Atmos is about synthetical, specular sources. You can't *mic* an Atmos field, but have to *compose* it. Third order ambisonics on the other hand *is* a technology you can so-and-so capture from the real world. Plug-and-play with spatial sound, to a degree. To me it sounds just stupid to bring in all of the "spatial objects" nonsense, when all it does is to add complexity and weight to the abstraction. Similar why DCPs (Digital Cinema Packages) encode color in CIE XYZ (you can encode invisible "colors"). Don't even get me started... XYZ is there because it's derived from the tristimulus theory at the physical level. Its weighting functions take on negative values only because the optimum transform to "color" call for them, and because we want the XYZ space to stay positive. Human vision then isn't quite like this, nonlinear as it is. So when charted out in the linear XYZ space, vision takes on a wonky, though convex, shape. As such, the "invisible" colors are a mathematical artifact. They are not an intrinsic part of the color space, but rather the complex side conditions of which XYZ values you are allowed to use in order not to encode imaginary colors are the way we model the truth about how human vision works. If you went out of gamut, it's not that "an imaginary color has suddenly been discovered", but that you failed to respect the boundary conditions engendered by the -- rather well-defined -- restrictions of the gamut. I guess the idea also was not to restrict the color space to the limits of any existing device. Indeed it was not. The idea was to start with linear tristimulus theory which was already known to be true, and then to model the newer (still rather old) opponent process theory of color within it. CIE's various standards rather successfully do just that. Or maybe they just want to fight pirated copies by filling up the disks faster ;-) I think this is the most likely explanation. Because, you know, Dolby is Dolby. It's always gone the Intellectual Property route, throughout its existence. Hell, at one time they refused to let anybody licence their noise reduction algorithms except as implemented by their analogue chips. Fuck, I don't think they even now permit anybody to implement SR, A, B, C, S, god forbid Prologic-II(x) in software. And they just keep on "inventing" -- not unlike one of our Finnish national prides ABLOY (lit. "Aktie Bolaget Lukko Osakeyhtiö", roughly "plc. Lock Plc.") keeps churning out newer and newer designs of keys in order to keep them under trademark and design rights. -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3751464, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
Re: [Sursound] Reynolds mics
On Wed, Apr 06, 2022 at 02:57:51AM +0300, Sampo Syreeni wrote: > I ask because theory-wise pantophonic and periphonic soundfields > shouldn't be captured the same way, There is no such thing as a 'pantophonic sound field'. We don't live in Flatland. All microphones operate in 3D space. Unless you mean a sound field with all sources in the horizontal plane of the mic. Then it is just a subset of a 3D sound field, and a conventional AMB mic will capture it correctly. > nor do they represent even the same encoding system. How does a sound field 'represent an encoding system' ? Your statement may be grammatically correct but it has no meaning. > people seem to do whathever, and don't even quantify their > secret sauce. Because there isn't any. The same applies to decoder design. Unless your speakers are infinitely long vertical line sources and radiate only in the horizontal plane, your system is a 3D one. Ciao, -- FA ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
Re: [Sursound] Reynolds mics
Hello Jack, > 25 Mar 2022 - Jack Reynolds : J> For windshields I have custom made Rycote BBGs that sit the array J> at the centre of the windshield. may i ask what are the diameters of the mic - head and body? -anders ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
Re: [Sursound] Reynolds mics
Hi Sampo! I am here if there’s anything you want to know. My marketing approach so far has been word of mouth really. I have been developing the designs with much field testing help from Axel and intended the mics to be as quiet and clean sounding as possible and also to be very difficult to break while camped out in the jungle. Waterproof Lemo connectors and 3D printed nylon makes for a much more robust product than the soundfields. They are based on the classic tetrahedron of cardioids and there’s not much more going on that. Cheers Jack Sent from my iPhone > On 6 Apr 2022, at 01:03, Sampo Syreeni wrote: > > On 2022-03-26, Chris Woolf wrote: > >> Jack has been conversing with me since then off-list, and I've clearly >> managed a bit of unintentional promo on his behalf! > > A bit of promo is not bad in these circles: quite obviously ambisonic (and > other principled high order) technologies need a bit of a commercial and > social boost nowadays. > > But why don't you then bring Jack back into the fold, too? It'd be a *hoot* > to discuss his technical and marketing choices in here. Maybe have a bit of > to-and-fro abotu them. :) <3 > -- > Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front > +358-40-3751464, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 > ___ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit > account or options, view archives and so on. ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
