Talk:Ambisonics

More speakers are better

Until recently, the article included, "(in general, the more speakers, the higher the accuracy of the reconstructed soundfield)". This was removed by User:Nettings with the edit summary, 'removed "the more loudspeakers, the better". daniel has shown that rE suffers from too many loudspeakers.'

It is still true, however, that six speakers are better than four, and that eight are better than six. The problem Daniel's theoretical work exposed was only with very large numbers of speakers. The two points are not in conflict, so can we find a form of words that accommodates both? HairyWombat 15:17, 16 December 2013 (UTC)

It's not exactly a theoretical problem. And eight speakers for first-order horizontal is already stretching it - I doubt you will find them preferrable to six, really. The more speakers, the higher the accuracy (for a given order) is definitely a myth. Besides, this whole article includes waaay too much information that is not really relevant to an introductory article in an encyclopaedia. Nettings (talk) 15:51, 16 December 2013 (UTC)

Here is a very good elaboration on the problem with too many speakers: Solvang, Audun, "Spectral Impairment for Two-Dimensional Higher Order Ambisonics", JAES Vol.56/4, 2008. If you cannot access this, I can send you an excerpt by mail if you're interested, just get in touch. Nettings (talk) 09:22, 20 December 2013 (UTC)

Six speakers are better than four. This has never been questioned. I have not read this JAES paper, but the results from listening tests are mixed even with many speakers. HairyWombat 17:31, 20 December 2013 (UTC)

Time permitting, I will add some elaboration on this inspired by Wiggins, who made a very nice rE plot for the corner case of three speakers (where horrible speaker detention is evident), and shows the improvement in the rE plot with four and six speakers. So at the low end of the scale, "some more speakers than the absolute minimum == better localisation". But the generalisation "more == better" is demonstrably wrong, see Daniel and Solvang. As the speaker number increases more, spectral issues and phasing will dominate the perception, so that there is a subjective loss in quality for $N_{speakers}\gg 2\ell +1$. From my own experience, I'd be vary of subjective listening reports based on just a single system experience, because reverberant room acoustics tend to mask phasing issues that are very evident (and obnoxious) in dry acoustics. Whereas the objections from Solvang and Daniel are quantifiable. - Btw, thanks for your helpful hints on proper archival and indentation. If you find other places where my edits do not adhere to WP best practises, I'd love to learn about them.Nettings (talk) 11:17, 21 December 2013 (UTC)

Concise single source to support increased interest in Ambisonics

Hi, I just added a statement to the initial section stating renewed interest in Ambisonics from research institutions and media companies. Before I add a looong list of recent papers from said parties to support this claim, does anyone know of a single source that will corroborate this fact more concisely? Nettings (talk) 16:59, 16 December 2013 (UTC)

Shortening the Ambisonics article

Hi *! I have taken the liberty of ruthlessly editing the article, to transform it into a first-class wikipedia citizen eventually. I realize that I've removed content that contains valid and valuable information, and which represents long and hard work by other people. The content is not lost, merely commented out, and can be cherry-picked at leisure. (Besides, Wikipedia does not lose anything and you can always revert my changes if you disagree). However, I felt that the previous state of the article required a heavy-handed clean-up effort. I hope we can arrive at a sub-page structure that leaves room for the interesting and diverse historical information on ambisonics while keeping the main article short and to the point, while transforming the anecdotal style to something that's more in keeping with encyclopaedic writing. (I'm picking this up as I go, so feel free to shorten my contributions even more!) I realize that there is currently too much "original research" (aka. stuff everyone knows) which needs backing up by citations, and that we are totally missing information on psycho-acoustic criteria and optimisations vs. physically correct sound field reconstruction. Time permitting, I will try to add some missing bits in the near future, and I hope that other Ambisonics enthusiasts will join in. Nettings (talk) 22:12, 16 December 2013 (UTC)

After extensive editing, the article is coming into shape, but almost back to its former length, unfortunately. The "Theoretical foundation" section is still woefully incomplete, it definitely needs a formulation of the SH and a connection to the Helmholtz equation. I suggest that whoever tackles this section properly splits it off into another subpage, maybe "Theoretical foundation of Ambisonics", and we add a {{Detail}} template at the end of the "Gentle introduction"... That way, we can keep the main page short and sweet while not glossing over important details.Nettings (talk) 16:29, 28 December 2013 (UTC)

This page is quite out of sync with modern ambisonic use and would benefit from a major update, if someone has the time. Might it be better to reorganise it as a page of what ambisonics does and how it is used, moving much of the mathematical foundation to a separate page? A lot of people work with ambisonics professionally these days, and there's plenty to say about what ambisonics does for them which would be interesting and useful for a wide audience; however, few of them actually know how the maths work and don't need to - it isn't necessary to understand what's possible and use modern tools. — Preceding unsigned comment added by 94.6.85.94 (talk) 19:10, 13 January 2022 (UTC)

Things to do as of 2013-01-04

• Expand section Theoretical foundation/Soundfield analysis with all-out attack on Kirchhoff-Helmholtz, wave equation and multipole expansion. I'm picking up the details as I go, so I'd appreciate someone more knowledgeable to beat me to it :) Nettings (talk) 13:18, 3 January 2014 (UTC)
• Expand section on History of Ambisonics. I added this section because the old page used to be all about history and very little about stuff that actually matters today, but there is lots of good information there that must be salvaged, without letting it clutter the important stuff. Depending on how much interesting material turns up, a sub-page might be warranted. Nettings (talk) 13:18, 3 January 2014 (UTC)

Psychoacoustics of spatial and directional perception

My general problem with the topic is that it does not actually deal with psychoacoustics, with is a psychometric. Rather, it employs a number of basic terms from acoustics, and borrowed from psychoacoustics, as if they were 'real', and exclusively metric. A simple example is that if a mono source needs to be 'placed' in a position which is between two loudspeakers, the signal will be transduced by both. Simply using precedence effect, a person sitting closer to one speaker will 'perceive' / interpret the sound as coming from that speaker rather than 'somewhere between' [sic] the speakers.

The Psychoacoustics section simply describes the dual-band (duplex) theory of sound localization first proposed by Lord Rayleigh around 1900, and used by Blumlein in his 1933 patent on stereo. It omits pinnae cues, but what is there is uncontroversial. Neither the article nor this talk page uses the phrase "somewhere between", so I am not sure what this refers to. Also, in Ambisonics, all speakers cooperate to localize a sound; a mono source is never fed to just one speaker. Because of this, the precedence (Haas) effect is not significant.74.205.216.149 (talk) 21:38, 8 July 2014 (UTC)

Another example is the use of the term 'near-field', without an adequate explanation of what it means in acoustics and recording. I find that there are lots of interesting terms related to this article, and the 'field' of ambisonics, however, in my experience, after over a decade of explanation and 'concert hall examples', sadly, I still hear it as messed-up mono.

I agree that near-field is not adequately explained. In Ambisonics, it only applies to decoder design, so it doesn't mean much in acoustics or recording. Finally, what you hear is what you hear, and nobody can argue with that. Others, however, do not hear messed-up mono (whatever that is).74.205.216.149 (talk) 21:38, 8 July 2014 (UTC)

For further reading on this area, while it is an older book, revised twice, I highly recommend: Spatial Hearing, The Psychophysics of Human Sound Localization, Jens Blauert, MIT Press, ISBN 0-262-02413-6. http://mitpress.mit.edu/books/spatial-hearing

<Spatial Hearing, The Psychophysics of Human Sound Localization, Jens Blauert, MIT Press, ISBN 0-262-02413-6>

Kaustin6969 (talk) 22:39, 7 July 2014 (UTC)

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Duane Cooper was the first to invent Ambisonics, but he is not mentioned in this article.

This article completely omits the work of Duane H. Cooper who was the first to file a patent about Ambisonics. This must be corrected! You can search the U.S. patent office, uspto.gov, for that information. A brief history is outlined in a sidebar of a white paper written by Floyd Toole after consulting Cooper's widow who was extremely cognizant of the events surrounding Cooper's work. (She has since passed away.) The white paper, which is based on a two-part article which appeared in Audio magazine in the mid-1990s, is available here: How Many Channels Cooper's 1972 Journal of the Audio Engineering Society paper is available here: Discrete-Matrix Multichannel Stereo (Shiga had little to do with the work, possibly circuit design or testing). Please, let's get this history right. It was Cooper's patent or patents that were part of the NRC pool. --184.98.185.210 (talk) 10:02, 28 September 2018 (UTC)JB

Only the abtract of the AES paper is generally available at your link; the paper costs $33 for non-members of the AES. The complete paper is available here. Also, I was not able to download the PDF file you link to (not sure why). That said, Duane H. Cooper developed the UMX quadraphonic system, but UMX was not Ambisonic. Cooper's patents were part of the patent pool because the UMX system was a pivotal part of the Ambisonic UHJ Format, and the 'U' in UHJ is there to acknowledge this. The AES paper you link to is a reference in the Wikipedia article on Quadraphonics, so you might want to expand that section. 74.205.219.233 (talk) 17:04, 28 September 2018 (UTC)

Gerzon influenced by earlier work of Cooper and Shiga

F. Rumsey, Spatial Audio, Oxford: Focal Press, 2001

Linn C Doyle (talk) 03:43, 28 November 2020 (UTC)

The "How Many Channels" PDF can be found here. It doesn't state that Cooper invented Ambisonics, only that "The basic idea for this form of surround sound was patented first by Duane Cooper." In the article "What’s wrong with quadraphonics" Michael Gerzon describes both UMX and Ambisonics as "Harmonic Synthesis or kernel systems". AFAIK full bandwidth three channell UMX can losslessly transformed to horizontal first-order B-Format (WXY). See also [1].

Was UMX ever specified for encoding height and full periphonic playback? I couldn't find anything. If UMX was horizontal-only, how did Duane Cooper invent Ambisonics? Though I think UMX is worth mentioning as the Comparison to other surround formats does describe UMX very well.

80.187.116.159 (talk) 10:43, 11 August 2021 (UTC)

Confusion between Ambisonics "order" and spherical harmonics "order"

I found sometimes confusing the description of Ambisonics in terms of order. A first order Ambisonics seems to refer to the first degree of the spherical harmonics which has three orders. Is this confusion unavoidable? Julovi (talk) 08:40, 17 August 2020 (UTC)

This is unavoidably the standard nomaclature Linn C Doyle (talk) 03:45, 28 November 2020 (UTC)

Formulas for decoding

I'd like to ask if the formulas in section "Decoding" are correct. Is it correct to multiply by sqrt(8) at the end? Shouldn't that be a division by sqrt(8)? Does anybody have a reference for these formulas? Waldmaus (talk) 07:28, 22 October 2020 (UTC)

These decoders work but T-Designs would be more appropriate really?Linn C Doyle (talk) 03:45, 28 November 2020 (UTC)

FuMa -> AmbiX

In ye grande age of 2020 is it not surely time to move this article from Furse-Malham to AmbiX definitions? Linn C Doyle (talk) 03:48, 28 November 2020 (UTC)