* Significantly changed from the previous version
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By anonymous FTP from ftp.omg.unb.ca (131.202.34.4) in the directory /pub/ambisonic (ie from file://ftp.omg.unb.ca/pub/ambisonic/). The file is called faq_v2_6.html or something similar, and is suitable for viewing with Mosaic and other WWW browsers. PostScript and text files derived from this HTML source file can be found in the same directory.
It is posted periodically to the Usenet newsgroups rec.audio.tech, rec.audio.pro, rec.audio.misc, rec.audio.opinion, rec.answers and news.answers.
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The FAQ still contains a few `?'s. If you can complete any of them, please let me know. If you have more information, please e-mail, post or fax it to me.
Many thanks,
Martin Leese
University of New Brunswick
Department of Geodesy and Geomatics Engineering
Post Office Box 4400
Fredericton, N.B.
Canada E3B 5A3
E-mail: mleese@omg.unb.ca
WWW:
http://www.omg.unb.ca/~mleese/
Tel: (506) 453-4969
Fax: (506) 453-4943
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Then there was stereo with directional information spread along a line in front of the listener.
In real life, of course, sound reaches our ears from all directions. Surround sound attempts to improve the realism of the perceived sound by providing information from all directions, not just from in front of the listener.
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Ambisonic technology is based on a meta-theory (a theory of theories) of sound localisation developed by Michael A Gerzon when he was with the Mathematical Institute, University of Oxford (see the Gerzon 1992 reference). Ambisonic decoder design aims to satisfy simultaneously and consistently as many as possible of the mechanisms used by the ear/brain to locate sounds. The Gerzon theory takes account of non-central as well as central listening positions.
In an Ambisonic decoder the spherical harmonic direction signals, W, X, Y and Z, are passed through a set of shelf filters which have different gains at low and high frequencies designed to match different ways the ear/brain locates sounds. (The different localisation mechanisms operate below and above about 700 Hz.) The speaker feeds are then derived by passing the outputs from the shelf filters through a simple amplitude matrix. An important aspect of Ambisonic decoder technology is that it is only at this final stage of processing that the number and layout of speakers is considered.
The listening area for Ambisonic Surround Sound is comparable with that for conventional stereo, but larger.
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The fact that the Z component can be recorded creates the opportunity for periphonic (full-sphere) reproduction. Periphony requires speakers to be placed above and below the height of the listeners' ears.
Readers familiar with microphone techniques will realise that the W and Y spherical harmonic components are equivalent to the M and S components of the M-S stereo recording technique. Ambisonics is a natural extension of this recording technique to three dimensions.
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In contrast, Ambisonics attempts to recreate for the listener the complete sound field of the original performance. A particular number of speakers is not assumed and the technology can use various numbers and speaker layouts. With the Ambisonic Surround Sound system all of the speakers cooperate to locate a sound in its correct position.
A problem with the quadraphonic systems was that they did not work, and could never have been made to work because they were based on false premisses. This is explained in detail in the Sommerwerck 1984 reference, part I. In contrast, Ambisonics does work.
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Dolby Motion Picture matrix encoding (Dolby MP) is an encoding system, similar to the SQ quadraphonic system, designed for motion picture sound tracks. Four channels are encoded; left, centre, right and a mono surround channel. Dolby Stereo is the result of this encoding. Dolby Surround is a decoding process designed to decode Dolby Stereo in the living room. Pro Logic is an active decoding process, also designed for the living room. Lucasfilm Home THX is an enhancement of Pro Logic.Dolby Surround AC-3 is described in technical publications available from Dolby Laboratories Inc, info@dolby.com, and on the Dolby WWW page (http://www.dolby.com/). These suggest that:
AC-3 is a digital encoding technique that exploits "audio masking" to achieve high bit-rate reductions. AC-3 can be used to encode between 1 and 5.1 audio channels. Dolby Stereo Digital film sound format uses AC-3 to encode 5.1 audio channels onto film stock. The 5 channels, left, centre, right, right surround and left surround, are all full bandwidth. The .1 channel is a band limited (20 Hz to 120 Hz) bass effects channel. Dolby Surround AC-3, also called Dolby Surround Digital, is the consumer equivalent of Dolby Stereo Digital film sound and is also based on AC-3 coding of 5.1 channels.Ambisonic Surround Sound differs from the Dolby surround systems in that the former is designed for the realistic reproduction of music while the latter, to enhance the enjoyment of motion pictures.
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The `H' has no meaning. The BBC called the first matrix they assessed Matrix A, and then worked up the alphabet.
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Established transmission media (LP, FM radio, CD) are two-channel and, unfortunately, it is impossible to obtain reasonable surround sound using only two of the B-Format signals. To overcome this two-channel UHJ matrix encoding was developed. Not only can two-channel UHJ be decoded back into horizontal surround sound, but also this C-Format is mono and stereo compatible.
When two-channel UHJ is played in stereo, the front- and side-stage material is reproduced with sharply defined images. The rear-stage material is reproduced, but given a less focussed, more "recessed" quality. This helps to provide an audible distinction between front and rear sounds when played in stereo.
When two-channel UHJ is played in mono, sounds from all directions, including due back, are reproduced in the single speaker at a level within 5 dB of one another.
Two-channel UHJ was extended into a hierarchy of C-Formats for 2, 2.5, 3 and 4 transmission channels, termed BHJ, SHJ, THJ and PHJ, respectively. The extra channels are used to augment the two base channels to give improved horizontal surround sound and, for four-channel UHJ (PHJ), periphonic (full-sphere) surround sound. In practice, only two-channel UHJ (BHJ) encoded material has ever been released. For this reason UHJ has become a synonym for BHJ, and UHJ is the symbol you will see on LPs and CDs.
The advantages of UHJ over B-Format are that it is mono and stereo compatible, and allows horizontal surround sound to be transmitted using two-channel media. The disadvantages of UHJ are that both encoding and decoding require the use of 90 degree phase shifters, and that encoding into only two channels requires compromise. ("No-compromise" horizontal surround sound requires three transmission channels.) It is UHJ which has caused Ambisonics to be described as a "matrix" system, but Ambisonics is much more than UHJ.
Readers interested in seeing the set of encoding/decoding equations should consult the appendices of the Gerzon 1985 reference.
UHJ is more symbolism than initialism. The `U' stands for Universal, and is taken from the UMX quadraphonic system which pioneered the technique of using supplementary channels to enhance directional resolution. The `H' represents the BBC's Matrix H and their work on mono and stereo compatible matrices. The `J' is taken from System 45 J, the name of the original two-channel UHJ system. (The `J' was simply a code letter used to describe a possible surround sound system.)
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SHJ specifies how W, X and Y can be encoded into 2.5 channels, called Left, Right and T, where the T channel is of reduced bandwidth (5 kHz). The original intention was to provide the reduced bandwidth channel in broadcasting by additional modulation of the 38 kHz sub-carrier. Presumably RDS, Minicall, etc, kills this possibility.
THJ specifies how W, X and Y can be encoded into three channels called Left, Right and T. This is the "no-compromise" horizontal C-Format.
PHJ specifies how W, X, Y and Z can be encoded into four channels, called Left, Right, T and Q, and is the "no-compromise" periphonic C-Format. Periphonic (full-sphere) reproduction requires speakers to be placed above and below the height of the listeners' ears.
BHJ, SHJ, THJ and PHJ are all inter-compatible. That is to say, to go from one member of the set to the next you add or delete additional signals without changing those that remain. A beauty of this is that each member of the UHJ set is mono and stereo compatible. In addition, a BHJ decoder, for example, can decode SHJ, THJ and PHJ material simply by ignoring the extra T and Q channels.
Version 1.0 of this FAQ suggested encoding a third channel into the `subcodes' of a CD to give THJ or SHJ. It transpires that the bandwidth available in the subcodes is less than 2 kHz using 16 bits, so this ain't gonna fly.
It is possible, however, to use "buried data" to encode a third channel of reduced bandwidth onto a CD such that an existing CD player is unaware the channel exists. This would allow SHJ encoded CDs to be produced that are completely compatible with conventional stereo CD players. That is to say, a stereo system would produce stereo, a BHJ decoder would produce surround sound, and an SHJ decoder (fed from a CD player with special digital electronics) would produce even better surround sound. All this from the same CD! The technique is too complicated to describe here, and interested readers should consult the Gerzon and Craven 1995 reference.
Peter Knight has pointed out that the CD format specification includes a four-channel quad format that would be suitable for PHJ encoded material. The problem, of course, is that existing CD players are not quad CD "aware" and would produce a mishmash if asked to play a quad CD. He has also pointed out that quad CDs have to be spun twice as fast as stereo CDs and have only half the playtime.
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A key part of Ambisonic decoding is the use of shelf filters. These give different gains at low and high frequencies to satisfy different mechanisms used by the ear/brain to locate sounds. (The change occurs at around 700 Hz.) Dolby MP encoding is similar to the SQ quadraphonic system and, unfortunately, SQ decoding requires that no shelf filters be used. As a consequence, SQ (and therefore Dolby MP) decoders cannot be designed to give full Ambisonic results; there is even a mathematical theorem to this effect.
Integrex Limited manufactured an Ambisonic decoder which could decode almost every quadraphonic system, including SQ. The design of this decoder has been published (see the Gerzon 1977b reference), and the SQ mode used Ambisonic technology only to give more freedom over the number and layout of speakers.
Of course, there is nothing to prevent you reproducing Dolby MP encoded material through an Ambisonic UHJ decoder. The seamless coherent sound field which results has been described as "superb", but it will not be what the sound engineer who created the recording intended you to hear. The question of whether UHJ decoding of Dolby MP encoded material is preferable, is most easily answered by listening.
Dolby MP will always suffer from non-existent sound imaging to the rear and side of the listener. While not a serious impediment to the enjoyment of motion pictures, these limitations do make Dolby MP encoding unsuitable for music. I am old enough to remember SQ; like all the quadraphonic systems, it sucked.
It is also strange that the Dolby MP crowd seems determined to repeat the mistakes made by the quadraphonic crowd, namely a desire for channel separation (which merely calls attention to individual speakers as sources of sound) and a penchant for active decoders (which cause fatigue in listeners).
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Dolby Surround AC-3 does not use matrixing and the five audio channels have complete separation. Sadly, this is not sufficient for realistic surround sound reproduction. The problem is the "pair-wise" mixing style. Dolby Surround AC-3 is just a delivery mechanism and is not tied to pair-wise mixing, however, to date all Dolby Surround AC-3 movie sound tracks have been mixed using the pair-wise mixing style.
Pair-wise mixing is also called "pan-potting", "amplitude mixing" and "intensity stereophony". It mixes signals into the feeds for a pair of speakers to create the illusion that a sound is coming from a point somewhere between the speakers. The apparent location of each sound is determined only by the relative amplitude of that sound in the two speakers. Almost all stereo recordings are mixed using the pair-wise mixing style.
The ear/brain locates sounds using phase differences between the ears as well as amplitude differences. (In truth, phase is used to locate sounds with frequencies between 150 Hz and 1.5 kHz, amplitude for frequencies between 300 Hz and 5 kHz, and other cues for frequencies above 3.5 kHz. Note that the three frequency ranges overlap.) Fortunately, when a pair of speakers are in front of the listener and separated by 60 degrees or less, the amplitude changes mimic the correct phase changes and the pair-wise mixing style works well. Unfortunately, pair-wise mixing works poorly when the speakers are to the rear of the listener and not at all when they are to one side. (See the Gerzon 1985 or the Fellgett 1981 reference. Better still, try it yourself!) This means that any surround sound system that relies on pair-wise mixing between adjacent speakers must fail. This is as true for Dolby Surround AC-3 as it was true for the quadraphonic systems. Such absolute statements can be made because the way that the ear/brain localises sound has not changed.
One solution is for sound engineers to use a mixing style other than pair-wise mixing to mix the Dolby Surround AC-3 format. Happily, an alternative exists - Ambisonics.
Another solution is for the 5.1 pair-wise mixed channels to be converted into W, X and Y signals by projecting each of the five stereo pairs onto 72 degrees of the horizontal sound stage, and to then use Ambisonic technology to reproduce the sound field. I am not sure whether this is technically feasible.
As with Dolby MP, these limitations of pair-wise mixing are not a serious impediment to the enjoyment of motion pictures. They do, however, make pair-wise mixed Dolby Surround AC-3 unsuitable for music.
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HQAD will be the first real opportunity for periphonic (full-sphere) Ambisonic source material to be released commercially. A periphonic decoder was demonstrated as long ago as 1980, but to date domestic full-sphere surround sound reproduction has been enjoyed only by a few enthusiasts with access to Ambisonic master tapes. The advent of HQAD and its accommodation of Ambisonics will, for the first time, bring full-sphere surround sound within the reach of everybody.
The advantages of periphony over horizontal surround sound are not only the possibility of using height for special effects but also that recordings sound more lifelike and less "hi-fi". For example, the timbre of orchestral instruments take on the "feathery" quality heard at live events.
Practical periphony requires six or eight speakers, some of which must be placed above and below the height of the listeners' ears. Readers interested in seeing the various speaker layouts which are possible should consult the Gerzon 1980 reference.
Of course, horizontal Ambisonic decoders will still be able to produce "no compromise" horizontal surround sound simply by ignoring the Z (height) signal.
Copies of A Proposal for the High-Quality Audio Application of High-Density CD Carriers (Version 1.2) can be obtained from:
J R Stuart, Chairman ARASection headings are shown in the Contents list.
c/o the Secretariat
Acoustic Renaissance for Audio
Stonehill
Stukely Meadows
Huntingdon
Cambridgeshire
United Kingdom
Tel: +44-1480-52144
Fax: +44-1480-451587
E-mail: ara@meridian.co.uk
WWW: http://www.meridian.co.uk/ara/Hirokazu Negishi, Founder ARA
Research & Development Headquarters
Cannon Inc Shinjuku Office
7-1 Nishi-Shinjuku 2-chome
Shinjuku-ku
Tokyo 163-07
Japan
Tel: +81-3-3344-8409
Fax: +81-3-3349-1399
E-mail: negishi@gcds.cannon.co.jp
By Nimbus Records.
By Unicorn (now Unicorn-Kanchana).
By Music from York (now York Ambisonics). They also released UHJ encoded cassettes.
Libra Realsound may only have released UHJ encoded cassettes. Address/telephone anyone?
By IMF Electronics (see TDL Electronics Limited).
I am not sure whether Hyperion Records Limited released LPs or just sold them. Telephone/fax number anyone? Do they still exist?
Hyperion Records LimitedSection headings are shown in the Contents list.
PO Box 25
Eltham
London SE9 1AX
United Kingdom
All Nimbus recordings are UHJ encoded.
Nimbus RecordsUnicorn-Kanchana have abandoned Ambisonics, but there are still sixteen UHJ encoded recordings in their catalogue.
Wyastone Leys
Monmouth
Gwent NP5 3SR
United Kingdom
Tel: +44-1600-890682
Fax: +44-1600-890779Nimbus Records
PO Box 7746
Charlottesville
VA 22905 7746
USA
Tel: +1-804-985-8555 (also 1-800-944-1341)
Fax: +1-804-985-3953
E-mail: NimbusCD@aol.com
Unicorn-KanchanaYork Ambisonics.
14 Hillgate Place
London W8 7SJ
United Kingdom
Tel: +44-171-727-3881
Fax: +44-171-243-1701
York AmbisonicsCollins Classics have abandoned Ambisonics, but there are still two or three UHJ encoded titles in their catalogue.
PO Box 66
Lancaster LA2 6HS
United Kingdom
Tel: +44-1524-823020
Fax: +44-1524-824420
Collins ClassicsOndine Inc have abandoned Ambisonics, but there are many UHJ encoded titles in their catalogue.
Premier House
10 Greycoat Place
London SW1P 1SB
United Kingdom
Tel: +44-171-222-1921
Fax: +44-171-222-1926
Ondine IncFinlandia have abandoned Ambisonics. I do not know how many UHJ titles remain in their catalogue.
Fredrikinkatu 77 A 2
SF-00100 Helsinki
Finland
Tel: +358-0-492-348
Fax: +358-0-493-956
FinlandiaUHJ encoded CDs have been released by the following labels. Can anybody provide addresses?
PO Box 169
FIN-02101 Espoo
Finland
Tel: +358-0-435-011
Fax: +358-0-455-2352
Pony Canyon (they have abandoned Ambisonics)The SNH record label is also supposed to have released UHJ encoded titles. Can anybody expand the initialism or supply an address?
EMI
KPM (EMI)
RCA Victor (CDs by Cowboy Junkies)
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Minim Electronics Limited marketed a range of three decoders, the AD 7, AD 8 and AD 10, and also a printed circuit board module for enthusiasts to incorporate into their own projects.
IMF Electronics assisted in the development of Ambisonics and manufactured a decoder, the D20B. Part of the company was resurrected under the name TDL Electronics Limited, but it is unlikely that they have had any interest in Ambisonics.
TDL Electronics LimitedUp to 1981, Integrex Limited offered an Ambisonic decoder which could decode SQ, QS, UMX and Matrix H/HJ as well as UHJ. The Company is alive and kicking, but no longer has any involvement in Ambisonics or the hi-fi business.
Unit 2, Pilot Trading Estate
High Wycombe
Buckinghamshire
United Kingdom
Tel: +44-1494-441191
Fax: +44-1494-461803
Integrex LimitedAbacoid Limited produced a Professional Ambisonic Decoder, the PAD 9211. Does anybody know if they still exist? The telephone number listed in previous versions of this FAQ is no longer a business number.
Portwood Industrial Estate
Church Gresley
Derbyshire DE11 9PT
United Kingdom
Tel: +44-1283-551551
Fax: +44-1283-550325
Abacoid LimitedTroy manufactured an Ambisonic Processor [Decoder], the TA 110P, for use in the car. Troy currently have no plans to restart manufacture.
110A St Margarets Road
Hanwell
London W7 2HF
United Kingdom
Alan SextonNAD developed inexpensive Ambisonic decoders. Does anybody know if they were ever offered for sale? The telephone number listed in previous versions of this FAQ is no longer a business number.
Troy
Charters Road
Sunningdale
Ascot
Berkshire SL5 9QD
United Kingdom
Tel: +44-1344-21552
NADAnd one for our antipodean readers; Audiotech Industries offered an Ambisonic decoder. Details anyone?
683 High Street
North Finchley
London N12
United Kingdom
Audiotech IndustriesSection headings are shown in the Contents list.
PO Box 8756
Auckland
New Zealand
Tel: +64-9-587-386
By Minim Electronics Limited. When I last spoke to them in January 1995, they were about to revamp their offerings.
Minim Electronics LimitedAudio Design manufacture a Reference Ambisonic Decoder. This is intended for professional use, and is priced accordingly. The decoder is configured for four speakers and is distributed by Cepiar Limited. Cepiar are also planning to release a consumer Ambisonic decoder in the second half of 1996.
Lent Rise Road
Burnham
Slough SL1 7NY
United Kingdom
Tel: +44-1628-663724
Cepiar LimitedIn March 1993, Sound & Vision (see References) reviewed the Onkyo TX-SV909PRO A/V Receiver which incorporates an Ambisonic decoder. When in Ambisonic mode, the receiver is configured only for four speakers. The successor to the 909PRO is the Onkyo 919THX, but this does not incorporate an Ambisonic decoder.
Debden House
11 St Ethelwold's Close
Ely
Cambridgeshire CB6 3AX
United Kingdom
Tel: +44-1353-666818
Fax: +44-1353-666819
Onkyo USA CorporationMeridian's 565 Digital Surround Processor, which can be configured for 4, 5, 6 or 7 speakers, incorporates an Ambisonic decoder.
200 Williams Drive
Ramsey
NJ 07446
USA
Tel: +1-201-825-7950
Fax: +1-201-825-8150Onkyo Europe GMBH
Hellersbergstrasse 4
4040 Neuss
Germany
Tel: +49-2131-120075
Fax: +49-2131-103306
Telex: 8517916 ONDU D
Meridian Audio LimitedThe October 1995 issue of Audio magazine contained an annual equipment directory that included Sansui and Legacy Audio as suppliers of Ambisonic receivers and decoders, respectively. The Sansui receiver, model RZ2900, does not have an Ambisonic mode, so this was a misprint.
Stonehill
Stukely Meadows
Huntingdon
Cambridgeshire
United Kingdom
Tel: +44-1480-52144
Fax: +44-1480-459934
E-mail: jrs@meridian.co.uk
WWW: http://www.meridian.co.uk/Meridian America Inc
3800 Camp Creek Pkwy.
Bldg. 2400, Suite 112
Atlanta
GA 30331
USA
Tel: +1-404-344-7111
Fax: +1-404-346-7111
When I last spoke to Legacy Audio in December 1995, they were still intending to add an Ambisonic mode to their Steradian product, but had not yet done so.
Legacy AudioVersion 2.2 of this FAQ suggested that Maplin Electronics plc offered an Ambisonic decoder kit. This was incorrect. In 1994, Electronics - The Maplin Magazine carried a series of articles on surround sound (see the Woodgate 1994 reference), but referred readers to Minim Electronics Limited for the supply of Ambisonic decoders.
3021 Sangamon Ave
Springfield
IL 62702
USA
Tel: +1-217-544-5252 (also 1-800-283-4644)
Fax: +1-217-744-7269
If anybody knows of other commercial Ambisonic decoders, will they please let me know. I am particularly interested to hear about stand alone Ambisonic decoders that are not bundled together with home theatre decoders.
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Ambisonics has suffered from the following:
Ambisonic technology places restrictions on the choice and placement of speakers. Specifically:
The disadvantage of using only four speakers is that sounds with spiky waveforms (audience applause, harpsichords, oboes) tend to be drawn away from their correct location and towards a speaker. Using five or six speakers gives considerably more robust side and rear imaging.
For periphonic (full-sphere) surround sound a minimum of six or eight speakers is required driven from at least four or five power-amps, respectively. Readers interested in seeing the possible speaker layouts should consult the Gerzon 1980 reference.
Auditorium decoders that can drive between 8 and 128 speakers are available (from Cepiar Limited). For domestic use the limiting factors are the cost of the necessary speakers and power-amps, and the practical problem of squeezing them into your living room.
The speaker feeds are each a simple weighted sum of the W, X, Y and Z signals after they have passed through the shelf filters. Readers interested in seeing the equation should consult the appendices of the Gerzon 1985 reference.
With the "old-type" Ambisonic decoders described above, the apparent position of the centre-front sound image varies as the listener moves from one side of the living room to the other. This is not a problem when reproducing music, but when used with TV the on-screen sounds can become misaligned with the on-screen pictures. "New-type" Ambisonic decoders, described in the Gerzon and Barton 1992 reference, produce a stable centre-front sound image that solves this problem. These decoders can be used with irregular speaker layouts, either five speakers with one at the centre-front or six speakers with two at the centre-front. The "new-type" Ambisonic decoders are not yet commercially available.
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If you want to know what Ambisonic Surround Sound sounds like, but cannot arrange to hear it for yourself, the results of an extensive domestic listening test are described in the Attewell 1982 reference.
Further information on Ambisonics is available from the Ambisonic and `B'-format User Group run by Donald G Maclennan. ABUG is an informal group of about 180 devotees. Donald keeps a database of members' interests and he is happy to put people whose interests overlap in touch with each other. The membership includes people from the pro sound industry, journalism, academia and individuals like me who are just interested.
Donald G MaclennanThis FAQ is aimed at the domestic listener. Two areas of Ambisonic technology which have been omitted deliberately are recording and studio processing. These topics deserve an FAQ of their own, but somebody else will have to create it; I have done enough. Readers interested in these topics might like to join an e-mail mailing list, called sursound, devoted to surround sound audio discussion and research. To join, send an e-mail message to majordomo@lists.uoregon.edu with the contents:
ABUG
51 Hillside Avenue
Plymouth
Devon PL4 6PS
United Kingdom
Tel: +44-1752-663229
Fax: by appointment
subscribe sursoundThe list owner is Jim Rusby.
end
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Michael Gerzon, 1977a, "NRDC surround sound system", in Wireless World, April issue, pages 36 to 39.
Prof P B Fellgett, 1981, "Ambisonics", in New Electronics, May issue, pages 38, 44, 46 and 48.
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Rustan Finndin, rustan@cd.chalmers.se
Peter Knight, P.J.Knight@bradford.ac.uk
Jun Guo, jguo@u.washington.edu
Jeffrey Silberman, ambisonx@well.com
Jimmy T Rusby, jrusby@darkwing.uoregon.edu
Dave Malham, dgm2@unix.york.ac.uk
Brian Lenharth, brianl@lsid.hp.com
David S Monett of Monett Media Inc
Peter G Craven, peter@occl-ox.demon.co.uk
Michael A Gerzon, 100274.1550@compuserve.com
William Sommerwerck, williams@washington.nwlink.com
Roger Dressler, rwd@dolby.com
Eero Aro, EERO.ARO@YLE.YLE.mailnet.fi
Jeffrey Silberman maintains one of the very few B-Format studios in the USA. He would love to hear about any others.
Jeffrey SilbermanDavid S Monett runs Monett Media Ambisonics. This is a wanttodo entity which will record anything worth recording (in their opinion) any place for free, or near free, provided the recordings are never subject to commercial release or broadcast use. They also have a periphonic (full-sphere) Ambisonic Surround Sound decoder.
21 Millay Place
Mill Valley
CA 94941
USA
Tel: +1-415-380-8273
Fax: +1-415-380-9414
E-mail: ambisonx@well.com
Monett Media AmbisonicsSection headings are shown in the Contents list.
400 Colony Square
Suite 200
Atlanta
Georgia 30361
USA
Tel: +1-404-870-9009 (ask for Ambisonics)
Fax: +1-404-870-9005
The following are registered trademarks of Dolby Laboratories Licensing Corporation:
DolbyFor more information contact Lily Cheung, Dolby's Intellectual Property Manager, lsc@dolby.com.
Dolby Surround
AC-3
Pro Logic (no hyphen)
Dolby Stereo
Lucasfilm and Home THX are both registered trademarks of Lucasfilm Ltd, whether used together or separately.
PostScript is a trademark of Abobe Systems Incorporated or its subsidiaries which may be registered in certain jurisdictions.
Mosaic is a proprietary trademark of the University of Illinois.
The following are not definitive in that I have been unable to contact directly the companies concerned. If anybody has e-mail or WWW addresses for them, please let me know.
QS is a trademark of Sansui.
SQ is a trademark of CBS Laboratories.
CD-4 is a trademark of Japan Victor (JVC).
Does anybody know if UMX is a trademark?
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As it [UHJ encoding] is the first system design based on a complete mathematical analysis of both system theory and human psychoacoustics it is possible to say with some confidence that no system appreciably different from it can exceed its performance in optimal surround-sound decoding, so that no further system change is ever likely to be needed for horizontal encoding. [From the Gerzon 1977a reference, pages 38 and 39]Nothing has happened in the last 18 years to suggest this statement is wrong.
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