1. INTRODUCTION
Key references are indicated by a "star" rating below. The more important the reference from the viewpoint of understanding Ambisonics, the more stars. Obviously, this assessment is partly subjective.

Many of the 1990s references include new developments in Ambisonic technology relevant to the digital/multimedia era, and not just a rehash of older versions of the technology.

Historically, many of the basic ideas of Ambisonics were discovered independently around 1971/72 by Duane Cooper and by Gibson et al. in the USA, and by Michael Gerzon and by Peter Fellgett in England. Thus there are at least four independent discoverers of the basic concepts.

References are listed more-or-less in chronological order. No attempt has been made to make this list complete. This listing is based on references easily to hand or listed on my computer. It therefore over-represents my own publications and under-represents those of others. This is not meant to be a slight to them. I hope that future versions of this listing will include many more of other's publications.

Despite the incomplete nature of this listing (I am aware of a number of other important publications, but cannot currently find the references), I hope that the information here will prove useful.

2. PUBLISHED ARTICLES & PAPERS
* D.H. Cooper & T. Shiga, "Discrete-Matrix Multichannel Stereo," J. Audio Eng. Soc., vol. 20 pp. 346-360 (1972 June) Correction ibid vol. 20 p. 493 (1972 July/Aug) (Basic paper on the Hierarchical ideas refined in Ambisonics)

O. Kohsaka, E. Satoh & T. Nakayama, "Sound Image Localization in Multichannel Matrix Reproduction," J. Audio Eng. Soc., vol. 20 pp. 542-548 (1972 Sept.) (Early experimental confirmation of the improved sound localisation of systems based on Ambisonic ideas).

P.B. Fellgett, "Directional Information in Reproduced Sound," Wireless World, vol. 78, pp. 413-417 (1972 Sept.) (One of several papers coming up with Ambisonic ideas at that time.)

* J.J. Gibson, R.M. Christensen & A.L.R. Limberg, "Compatible FM Broadcasting of Panoramic Sound", J. Audio Eng. Soc., vol. 20 pp. 816-822 (1972 Dec.). (Although primarily about FM broadcast methods for surround-sound, this paper describes the hierarchical approach both for horizontal and with-height surround sound based on directional harmonics and spherical harmonics also used in Ambisonics)

* M.A. Gerzon, "Periphony: With-Height Sound Reproduction", J. Audio Eng. Soc., vol. 21, pp. 2-10 (1973 Jan./Feb.) (A highly mathematical account of general with-height reproduction systems. Includes the fundamental theory of with-height directional encoding systems).

*** Michael Gerzon, "Surround Sound Psychoacoustics", Wireless World, vol. 80, pp. 483-486 (1974 Dec.) (The first, and clearest, publication of the psychoacoustic decoding theory behind Ambisonic decoding)

Michael Gerzon, "What's Wrong with Quadraphonics?", Studio Sound, vol. 16 no. 5, pp. 50, 51, 56 (1974 May)

M.A. Gerzon, "A Geometric Model for Two-Channel Four-Speaker Matrix Stereo Systems", J. Audio Eng. Soc., vol. 23, pp. 98-106 (1975 Mar.)

* M.A. Gerzon, "The Design of Precisely Coincident Microphone Arrays for Stereo and Surround Sound", preprint of the 50th Audio Engineering Society Convention, London (1975 March) (About the design of the SoundField microphone)

Peter Fellgett, "Ambisonics. Part One. General System Description", Studio Sound, vol. 17 no. 8, pp. 20-22, 40 (1975 Aug.)

Michael Gerzon, "Ambisonics. Part Two: Studio Techniques", Studio Sound, vol. 17 no. 8, pp. 24, 26, 28-30 (1975 Aug.) Correction: Studio Sound, vol. 17 no. 10, p. 60 (1975 Oct.)

M.A. Gerzon, "Recording Concert Hall Acoustics for Posterity", J. Audio Eng. Soc., vol. 23, pp. 569, 571 (1975 Sept.) (Describes the use of sound field microphone recordings of hall impulse responses to simulate reverberant spaces Ambisonically)

P.B. Fellgett & M.A. Gerzon, "Encoding Standards for 2-Channel Surround-Sound", Electronics Letters, vol. 11, pp. 518-519 (1975 Oct. 16) (A summary of the basic ideas beind optimising 2-channel surround sound encoding systems.)

M.A. Gerzon, "Compatible 2-Channel Encoding of Surround Sound", Electronics Letters, vol. 11, pp. 615-617 (1975 Dec. 11) (A summary of the details for optimising 2-channel surround sound encoding systems.)

M.A. Gerzon, "Maximum Directivity Factor of n'th-Order Transducers", J. Acoust. Soc. Am., vol. 60, pp. 278-280 (1976 July) (A mathematical proof of results about the directivity of high order microphones, relevant to periphony.)

* M.A. Gerzon, "The Optimum Choice of Surround-Sound Encoding Specification", Preprint no. 1199 of the 56th Audio Engineering Society Convention, Paris, (1977 Mar. 1) (About optimising 2-channel encoding for surround-sound - the theory behind UHJ. Very mathematical)

** Michael Gerzon, "NRDC Surround-Sound System", Wireless World, vol. 83 no. 1496, pp. 36-39 (1977 April) (A non-technical account of the work in the previous reference.)

P. Fellgett & M. Gerzon, "From quadro to surround sound", Elektor, vol. 3 no. 5, no. 25, pp. 5-19 to 5-25 (1977 May)

*** M.A. Gerzon, "Criteria for Evaluating Surround-Sound Systems", J. Audio Eng. Soc., vol. 25, pp. 400-408 (1977 June) (Although containing a lot of now-historic references to quadraphonics, this is still the best summary of the underlying philosophy of Ambisonics. Concentrates on the ideas, not on technical details.)

Michael Gerzon, "Multi-System Ambisonic Decoder", Part 1: "Basic Design Philosophy", Wireless World, vol. 83 no. 1499, pp. 43-47 (1977 July) Part 2: "Main Decoder Circuits", Wireless World, vol. 83 no. 1500, pp. 69-73 (1977 Aug.) later parts never written & published.

Michael Gerzon, "Don't say quad - say psychoacoustics", New Scientist, vol. 76, pp. 634-636 (1977 Dec. 8)

J.H. Smith, "The Sound Field Microphone," dB, pp. 34-37 (1978 July)

P.S. Gaskell, "System UHJ: A Hierarchy of Surround Sound Transmission Systems," Radio & Electron. Eng., vol. 49, pp. 449-459 (1979 Sept.) *** K. Farrar, "Soundfield Microphone," Wireless World, vol. 85 pp. 48-50 (1979 Oct.) and pp. 99-103 (1979 Nov.) (Best published reference on the design of the Sound field microphone.)

M.A. Gerzon, "Pictures of 2-Channel Directional Reproduction Systems", Preprint 1569 of the 65th Audio Engineering Society Convention, London (1980 Feb.)

* M.A. Gerzon, "Practical Periphony", Preprint 1571 of the 65th Audio Engineering Society Convention, London (1980 Feb.) (A relatively non-technical account of practical with-height full-sphere Ambisonic decoding).

John Borwick, Audio Commentary "Could 'Surround Sound' Bounce Back?", The Gramophone, 1981 Feb., 2 pages.

P B Fellgett, "Ambisonics", New Electronics, 1981 May, pp. 38, 44, 46 and 48.

C.P. Daubney, "Surround Sound: An Operational Insight," IBA Tech. Rev., no. 14 pp. 52-56 (1981 June): reprinted in Studio Sound, vol. 24, pp. 52-54, 56, 58 (1982 Aug.)

T. de Bono, "Gilgamesh, The Epic of the Epic," Broadcast Sound, pp. 10-12, 15 (1983 Jan./Feb.)

Richard Elen, "Ambisonic Mixing - An Introduction," Studio Sound, vol. 25 pp. 40-42, 44, 46 (1983 Sept.)

Nigel Branwell, "Ambisonic Surround-Sound Technology for Recording and Broadcast", Recording Engineer/Producer, Dec.1983, 4 pages.

*** M.A. Gerzon & G.J. Barton, "Ambisonic Surround-Sound Mixing for Multitrack Studios", Conference Paper C1009 of the 2nd Audio Engineering Society International Conference, Anaheim (1984 May 11-14) (Describes commercially available studio production technology for Ambisonics using multitrack methods).

*** M.A. Gerzon, "Ambisonics in Multichannel Broadcasting and Video", J. Audio Eng. Soc., vol. 33 no. 11, pp. 859-871 (1985 Nov.) (Possibly the best overview of classic Ambisonics.)

Michael Gerzon, "Three Channels. The Future of Stereo?", Studio Sound, vol. 32 no. 6, pp. 112, 114, 117, 118, 120, 123 & 125 (1990 June) (An account of Ambisonic ideas applied to 3-speaker frontal stereo.)

M.A. Gerzon, "Masking of Coding/Decoding Errors in Audio Data Compression", Proc. Inst. of Acoustics, vol. 12 part 8, pp. 175-182 (1990 Nov.)

M.A. Gerzon, "Problems of Error-Masking in Audio Data Compression Systems", Preprint 3013 of the 90th Audio Engineering Society Convention, Paris (1991 Feb.) (A technical discussion including the problems of "directional unmasking" of error artefacts in perceptual coding systems for surround sound.)

M.A. Gerzon, "Hierarchical Transmission of Multispeaker Stereo", Proceedings of the IEEE ASSP Workshop on Applications of Signal Processing to Audio and Acoustics, New Paltz, NY, (1991 Oct. 20-23)

M.A. Gerzon, "Directional Masking Coders for Multichannel Subband Audio Data Compression Systems", Preprint 3261 of the 92nd Audio Engineering Society Convention, Vienna (1992 Mar.) (A technical discussion concentrating on methods of "directional masking" of error artefacts in perceptual coding systems for surround sound.)

*** M.A. Gerzon, "General Metatheory of Auditory Localisation", Preprint 3306 of the 92nd Audio Engineering Society Convention, Vienna (1992 Mar.) (This is THE basic reference, mostly written in 1976, for the psychoacoustic theory behind Ambisonics. Highly technical and mathematical, but fundamental to design of Ambisonic decoders.)

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.)

M.A. Gerzon, "Panpot Laws for Multispeaker Stereo", Preprint 3309 of the 92nd Audio Engineering Society Convention, Vienna (1992 Mar.) (The use of Ambisonic methods to optimise pan-pot laws for 3- and 4-speaker frontal stage stereo.)

* M.A. Gerzon, "Hierarchical System of Surround Sound Transmission for HDTV", Preprint 3339 of the 92nd Audio Engineering Society Convention, Vienna (1992 Mar.) (A proposal for integrating Ambisonics and 5-channel cinema surround sound in a mutually compatible hierarchical system.)

*** M.A. Gerzon & G.J. Barton, "Ambisonic Decoders for HDTV", Preprint 3345 of the 92nd Audio Engineering Society Convention, Vienna (1992 Mar.) (A new generation of decoders for Ambisonics using more flexible speaker layouts than before, including cinema-type 5 or more speaker layouts. The new decoders give more stable frontal stage images than the 1970's technology did.)

M.A. Gerzon, (Article on Ambisonics, translated into Japanese), presented to the Japan Audio Society, Tokyo (1992 June 6)

*** M.A. Gerzon, "Optimum Reproduction Matrices for Multispeaker Stereo", J. Audio Engineering Society, vol. 40 no. 7/8, pp. 571-589 (1992 July/Aug.) (A fundamental paper on the application of Ambisonic ideas to frontal stage stereo using more than two loudspeakers. This technology is now known as the "Trifield" system.)

* M.A. Gerzon, "Hierarchical Transmission System for Multispeaker Stereo", J. Audio Eng. Soc., vol. 40 no. 9, pp. 692-705 (1992 Sept.) (The design of hierarchical transmission systems for multispeaker frontal stage stereo based on the previous paper.)

M.A. Gerzon, "Problems of Upward and Downward Compatibility in Multichannel Stereo Systems", Preprint 3404 of the 93rd Audio Engineering Society Convention, San Francisco (1992 Oct. 1-4)

M.A. Gerzon, "Compatibility of and Conversion Between Multispeaker Systems", Preprint 3405 of the 93rd Audio Engineering Society Convention, San Francisco (1992 Oct. 1-4)

** M.A. Gerzon, "Psychoacoustic Decoders for Multispeaker Stereo and Surround Sound", Preprint 3406 of the 93rd Audio Engineering Society Convention, San Francisco (1992 Oct. 1-4) (A useful up-to-date survey of psychoacoustic decoding of directional sound based on Ambisonic ideas, based on recent work.)

M.A. Gerzon, "Signal Processing for Simulating Realistic Stereo Images", Preprint 3423 of the 93rd Audio Engineering Society Convention, San Francisco (1992 Oct. 1-4) (Use of DSP methods for simulating images realistically placed in a virtual space, including distance and image-size simulation. Based on psychoacoustic methods rather than on physical modelling simulation.)

* M.A. Gerzon, "Microphone Techniques for 3-Channel Stereo", Preprint 3450 of the 93rd Audio Engineering Society Convention, San Francisco (1992 Oct. 1-4) (Perhaps the ONLY paper published on recording techniques optimised for 3-channel frontal stereo in the home.)

Ian G. Masters, "Ambisonics", Sound & Vision, Vol. 8, No. 6, 1993 March, pp. 26 & 43.

Richard Elen, article in Audio Media, early 1990s. Complete reference not to hand.

Keith Howard, "Meridian Digital theatre system," The Gramophone, vol.72, no. 859, pp. 247 & 250 (1994 Dec.) (review of equipment containing Ambisonic and "Trifield" decoders).

M.A. Gerzon & P.G. Craven, "A High-Rate Buried Data Channel for Audio CD", J. Audio Eng. Soc., vol. 43 No. 1/2 pp.3-22 (1995 Jan./Feb.)

A.W.J. Oomen, M.E. Groenewegen, R.G. van der Waal and R.N.J. Veldhuis, "A Variable-Bit-Rate Buried-Data Channel for Compact Disc," J. Audio Eng. Soc., vol. 43 No. 1/2 pp.23-28 (1995 Jan./Feb.)

3. GRANTED PATENTS with Michael Gerzon as inventor
"Sound Reproduction Systems" UK Patent 1,494,751 filed 1974 Mar. 26 [describes Ambisonic loudspeaker layout control]

UK Patent 1,494,752 filed 1974 Mar. 26 [describes pressure and velocity shelf filtering in Ambisonic decoders]

International applications corresponding to the above 2:
Canada 1020095 & 1017254,
France 7509457
Germany 2512287
Italy 1034532
Japan 1266685 & 1551072
Netherlands 181068
Switzerland 617303 & 625660
USA 3997725 & 4086433

UK Patent 1512514 (with Peter G. Craven)
[Sound field microphone]
Corresponding international applications:
France 7521673
Germany 2531161
Japan 1413913
Netherlands 186058
USA 4042779

UK Patent 1550627
[describes control of phasiness in Ambisonic decoders] Corresponding international applications:
Canada 1063035
France 7633920
Germany 2649525
Italy 1064312
Japan 1361504
Switzerland 622919
USA 4081606

UK Patent 1550628
[addition of third channel to Ambisonic encoding system, and associated "2-1/2-channel" and 3-channel decoders]
Corresponding international applications:
Canada 1061721
France 7707488
Germany 2711299
Italy 1078035
Switzerland 633400
Japan
USA 4095049

UK Patent 1548674
[use of loudspeaker matrixing for Ambisonic decoding] Corresponding international applications:
Canada 1068219
France 7720330
Germany 2728325
Italy 1107718
Switzerland 627035
USA 4139729

UK Patent 1552478
[delay compensation for varied loudspeaker distance in Ambisonic decoders] Corresponding international applications:
Japan 1589720
USA 4151369

UK Patent 2073556 filed 1980
[Ambisonic decoding via irregular loudspeaker layouts] Corresponding international applications:
Denmark 153269
USA 4414430
France, Germany, Netherlands EP0046765
Japan

The above does not include recent filings still pending.

[Added by Martin Leese] UK Patent ? filed 1998? ["New-type" Ambisonic decoders] Corresponding international applications:
USA 5757927

4. MISCELLANEOUS REFERENCES
Ambisonic Technology for Surround Reproduction of Sound, National Research Development Corporation (defunct), 1979, 2 pages.

Ambisonic Surround Sound System, National Research Development Corporation (defunct), 19??, 4 pages.

"Onkyo TX-SV909PRO A/V Receiver", Sound & Vision, Vol. 8 No. 6, 1993 March, p. 14. (This receiver incorporates an Ambisonic decoder.)

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Date: Tue, 28 Mar 1995 09:46:54 +0100 (BST)
From: DG Malham
Subject: Re: Ambisonic References

Michael - nice to hear from you, .... Your list of references is most useful, as it covers many I haven't currently written up in my lists. I will take the opportunity to put these on the Ambisonics 'Home' page I am maintaining on our World Wide Web server and, of course, if anyone wants to copy the HTML version when it appears on there (give me a couple of days, please!), they are most welcome. The Richard Elen article is;

Elen, R. 'Whatever Happened to Ambisonics' Audio Media, Nov. 1991, 16;50-54

BTW - the URL for the Ambisonics page is;
http://www.york.ac.uk/inst/mustech/3d_audio/ambison.htm
Contributions to this are most welcome.

Best wishes
Dave

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Date: Thu, 30 Mar 1995 23:45:48 -0800
From: Jeffrey Silberman (tm)
Subject: Re: Ambisonic References
The following is a listing of articles supplementing the one recently posted by Michael Gerzon. I have these on hand. Please let me know of additional ones that you may have so that we can compile a master list of surround sound and ambisonic articles and papers.

*Soundfield Microphone*
Calrec Sales Flyer
Farrar, Ken, "Soundfield Microphone" (extensive schematics)
Smith, Howard, "Ambisonics- The Calrec Soundfield Microphone," _Studio Sound_ (Oct. 1979)
McKenzie, A., "Calrec Soundfield Microphone," _Hi-Fi News_ (Dec. 1979)
Ford, Hugh, "Calrec 3B Soundfield Microphone System," _Studio Sound_ (Sept. 1982)
Whiting, John, "The Calrec Soundfield as a Stereo Microphone," _Studio Sound_ (Dec. 1983)
Denyer, Ralph, "Practical Soundfield," _Studio Sound_ (July 1984)
Hastilow, David, "Soundings on the Soundfield," _Studio Sound_ (Apr. 1989)
Lockwood, David, "AMS ST250- Height of Reality," _Audio Media_ (Dec. 1991)

*Ambisonics*
Carbines, Peter, "Ambisonics- Circles of Confusion," _Studio Sound_ (Aug. 1982)
Attewell, Trevor, "Ambisonics- the future of surround sound?"_Hi-Fi News_ Vol. 27 #9 (Sept. 1982)
Elen, Richard, "Ambisonics- Questions and Answers,"_Studio Sound_ (Oct.1982)
Sommerwerck, William, "Ambisonics Comes of Age," _The Audio Amateur_ (in 3 parts 3/84, 4/84 and 5/84)
Elen, Richard, "Ambisonics, A New Age," _Sound_ (1986)
Whiting, John, "Live Surround Sound," _Studio Sound_ (July 1988)
Furlong, Dermott, "Comparative Study of Effective Soundfield Reconstruction," AES, Preprint #2842, New York (1989)
Garman, Stuart, "Ambisonic Surroud Sound," (1991)
Furness, Roger, "Ambisonics- An Overview," _AES 8th Int. Conf
Whyte, Bert, "Home is Where the Hall is," _Audio_ (Mar. 1992)
Hendriksen, Ray, "Irish Ambisonics," _Line Up_
Sommerweck, William, "Ambisonics," _Stereophile_

*Other Papers of Interest*
Thiele, Gunther & Rebscher, Roland, "Enlarging of the Listening Area by Increasing the Number of Loudspeakers," AES, Preprint #2932(K5), Montreux 1990
Thiele, Gunther, "On the Performance of Two-Channel and Multi-Channel Stereophony," _Ibid_
Thiele, Gunther, "Further Developments of Loudspeaker Stereophony," AES, Preprint #2947, Los Angeles 1990
Gerzon, Michael, "Signal Processing for Simulating Realistic Stereo Images," AES, Preprint #3423(O-1), San Francisco 1992

WANTED:
Jagger, D.S., "Recent Developments and Improvements in Soundfield Microphone Technology," AES, Preprint #2064, Paris 1984

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Date: Fri, 31 Mar 1995 09:24:59 +0000
From: Bob Stuart
Subject: Re: Ambisonic References

Hi, Another reference you can add is my AES Paper:

Stuart, J. R. "Perceptual issues in Multichannel Sound Environments", AES San Francisco October 1994 Convention

Cheers,
Bob Stuart: Meridian Audio, Cambridge, England