US3906156A - Signal matrixing for directional reproduction of sound - Google Patents

Signal matrixing for directional reproduction of sound Download PDF

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US3906156A
US3906156A US288873A US28887372A US3906156A US 3906156 A US3906156 A US 3906156A US 288873 A US288873 A US 288873A US 28887372 A US28887372 A US 28887372A US 3906156 A US3906156 A US 3906156A
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signals
transmission
signal
transmission signals
presentation
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Duane H Cooper
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Priority to CA153,095A priority patent/CA997277A/en
Priority to GB1343875A priority patent/GB1411995A/en
Priority to GB4555872A priority patent/GB1411994A/en
Priority to FR7235624A priority patent/FR2156168B1/fr
Priority to DE2249039A priority patent/DE2249039C2/de
Priority to JP48102583A priority patent/JPS582520B2/ja
Priority to US05/468,279 priority patent/US3946165A/en
Priority to US05/468,238 priority patent/US3985978A/en
Priority to US05/578,078 priority patent/US3970788A/en
Publication of US3906156A publication Critical patent/US3906156A/en
Application granted granted Critical
Priority to CA252,645A priority patent/CA1006831A/en
Priority to CA252,644A priority patent/CA1006830A/en
Priority to CA252,646A priority patent/CA1006832A/en
Priority to CA252,648A priority patent/CA1006828A/en
Priority to CA252,647A priority patent/CA1006824A/en
Priority to CA252,643A priority patent/CA1006829A/en
Priority to US05/836,507 priority patent/US4152542A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
    • H04S3/02—Systems employing more than two channels, e.g. quadraphonic of the matrix type, i.e. in which input signals are combined algebraically, e.g. after having been phase shifted with respect to each other
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/00992—Circuits for stereophonic or quadraphonic recording or reproducing

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  • ABSTRACT Multidirectional sound signals are optimally matrixed to increase the psychoacoustic directional fidelity as compared with prior systems.
  • Four (or more) azimuthally spaced loudspeakers are fed from two transmission channels with very satisfactory directional sensing accuracy and full compatibility with conventional single-channel and two-channel reproduction equipment.
  • Further auxiliary transmission channels may be added to produce a form of discrete-channel capability having even greater azimuthal fidelity than obtained in speaker-identified channels, while at the same time maintaining compatibility both with conventional reproducing equipment and with equipment for the basic two-channel transmission of the invention.
  • the auxiliary channels may be transmitted in a relatively narrow frequency range, thus reducing the total bandwidth requirement for recording or broadcasting as compared with full conventional discrete channels.
  • This invention relates to reproduction of multidirectional audio program material with greater directionality and ambience than those of conventional stereo reproduction, and to the recording and/or transmission of program material for such reproduction. More particularly, the invention relates to the coding or mixing of directional sound information into a number of recording or transmission channels smaller (at least normally) than the number of sound sources to be reproduced and decoding or signal treatment and distribution of the content of these channels to reproducers differing in number or location from the sound-source locations for reproduction simulating presence at the original performance in psychoacoustic impression.
  • quadrasonic an extension of two-speaker stereo techniques to the reproduction of multidirectional program material with four loudspeakers to increase the sensory illusion of presence or ambience.
  • quadrasonic originated to describe systems wherein exciting or presentation signals for individual reproducers are maintained in separate and discrete form as separate signal channels, as in four-speaker reproduction from four-track tape.
  • the present invention flows from study of the weaknesses or inadequacies of the systems heretofore proposed, and lies in the devising of novel methods and apparatus of encoding and decoding multiple-source and multiple-reproducer signals which not only involve, in a 4-2-4 system, a minimum of sacrifice of the performance obtained with the respective reproducer signals maintained in separate channels throughout, but additionally provide much greater flexibility than previous such systems afiord, as well as providing considerable further advantage in supplemental extension to two further transmission channels where these are available, as later discussed.
  • the nature of the anomalies or directional ambiguities in signals intended to appear to the listener to come from particular directions in the prior art systems is not wholly identical in each case, nor are the sound directions from which the prior art matrixing systems produce such anomalous results the same.
  • Typical examples are opposite-phase reproduction from rear speakers and similar anomalies which result in more faithful reproduction of front-oriented sounds than rear-oriented sounds.
  • the anomalies are more or less negligible in psychoacoustic impression with most program materials, but become highly noticeable with materials with sound effects specifically designed for quadrasonic reproduction, wherein rear sounds are not merely supplementary.
  • the invention provides methods and apparatus whereby it is unnecessary to maintain, for satisfactory performance, a single predetermined set of positions of the loudspeakers with respect to the listener to produce satisfactory reproduction.
  • the systems of the prior art (including transmission in four discrete channels) require a single specific orientation of the loudspeakers with respect to the listener.
  • a pair of back speakers is added to the front speakers of a conventional stereo system to form a 2 plus 2 array.
  • the speakers are to be arranged in the form of a diamond or l-2-l, i.e., at opposite sides of the listener and at the center front and back.
  • the encoding and decoding of the present invention is capable of producing the same reproduction characteristics for all directions, and may be described as directionally symmetrical".
  • the meaning of this term as herein used may be most easily understood by considering the simple example of the reproduction of a sound whose source is successively moved to actuate each of four orthogonally located microphones in succession.
  • a listener who turns through corresponding successive 90 angles hears the sound source in wholly identical fashion as it is correspondingly moved through the four positions.
  • This property is inherent in a quadrasonic system with a separate signal channel for transmission of each microphone output but is not obtainable with prior art 4-2-4 matrix systems. As indicated above, this is particularly important in permitting use of new types of program material wherein there is to be conveyed a realistic impression of an independent sound-source (a voice or chorus for example) at a localized location rearward of the listener.
  • the directional symmetry of the matrixing permits simple signalconversion whereby the geometry of a loudspeaker system may be rotated with respect to the loudspeaker geometry assumed in the signal-production to permit wholly satisfactory reproduction of (for example) a recording or FM transmission designed for 2-plus-2 speaker orientation by a reproducing system with speakers arranged in the 1-2-1 form of a diamond, or vice versa.
  • the invention provides methods and apparatus whereby the number and arrangement of speakers to be used in reproduction is essentially unidentified in the signal transmission, which is universal and may be decoded into presentation signals for feeding any desired number and orientation of speakers.
  • the two encoded transmission channels may be decoded to produce, for example, six speaker-feed signals, with the speakers disposed in the form of a hexagon, the resultant listener sensation approximating that obtained with discrete six-channel transmission.
  • the invention has even more unique properties in its extension to transmission in larger numbers of channels, such as four.
  • the two-channel matrixing system hereinafter to be described produces loudspeaker presentation signals which may be shown to contain the maximum possible azimuthal localization information which can be conveyed with a two-transmission-channel matrix which is directionally symmetrical.
  • Such a system cannot be made discrete, i.e., a sound portrayed as emanating from the azimuthal direction coinciding with that of a speaker is always necessarily also presented by the two adjacent speakers, although in such reduced amplitude and in such phase relation that the psychoacoustic sound localization is satisfactory.
  • This pattern of presentation can be sharpened, i.e., the fractional ratio of the undesired-direction presentations to the center or desired-direction presentation can be reduced, only by addition of one or more further transmission channels adding to the directional acutance.
  • two further transmission channels are added to the basic system, with a quadrasonic speaker array, wholly discrete reproduction may be obtained, i.e., a sound which could be reproduced in only a single speaker by using an ordinary four-track tape recording can also be reproduced by the present system from a single speaker, with the others silent.
  • the performance is accordingly psychoacoustically indistinguishable from that produced in a four-channel system wherein the speaker signals are maintained wholly separated throughout.
  • the discrete matrix of the present invention is readily made wholly compatible with any type of conventional monaural or stereophonic reproduction.
  • the four-channel system of the invention is found to produce substantially better psychoacoustic localization of phantom? azimuthal locations, i.e., directional sound images which do not correspond to any actual speaker location, than conventional four-track presentation.
  • the discrete or sole operation of a speaker located directly at the source" azimuth is obgive. Thus bandwidth requirements are substantially reduced for transmission in media which would otherwise require transmission of the entire audio range in each transmission channel.
  • FIG. 1 is a schematic illustration of one type of quadrasonic sould reproduction system
  • FIG. 2 is a similar illustration of a variant type of quadrasonic sound reproduction system
  • FIG. 3 is a similar illustration, but differing from the previous FIGS. in the employment of noncorresponding source-signal and reproduction locations;
  • FIG. 4 is a schematic view illustrating certain angular relations employed in the invention.
  • FIG. 5 shows phasor diagrams of transmission signals formed in accordance with the invention
  • FIG. 6 is a block diagram of an exemplary singlesignal encoder embodying the invention.
  • FIG. 7 is a block diagram of a universal encoder for numerous sound signals embodying the invention.
  • FIG. 8 is a block diagram of one form of decoder incorporating the invention.
  • FIG. 9 is a block diagram of another form of decoder of the invention.
  • FIG. I is a block diagram of an adapter circuit for employing the decoder of FIG. 9 with conventional stereo signals;
  • FIG. II is a block diagram of an overall 4-4-4 mixing and transmission system according to the invention.
  • FIG. 12 is a matrix-equation representation of the encoding. decoding and presentation of the system of FIG. II;
  • FIG. I3 is a polar diagram showing the amplitude and phase of reproduction of a directional sound signal as a function of the azimuthal angle between each direction of reproduction and the direction whence it is sensed to originate by a listener, for the basic twochannel transmission system and for the four-channel transmission system, with a dotted showihg of characteristics later described.
  • FIGS. I through 3 there are shown basic forms of quadrasonic sound system which may bdvantageously employ the invention.
  • FIGS. I and 2 show systems which are, except for the matricesfor encoding and decoding transmission signals, the same as certain systems of the prior art. These exemplary systems are illustrated and described to facilitate understanding of the advantages and broad utility of the encoding and decoding (alternatively called matrixing and re-matrixing) of the present invention to be later described.
  • FIGS. I and 2 are alternate forms of quadrasonic systems heretofore employed with various matrixing systems.
  • an array or pattern of orthogonal microphones 20 or 200 at a program location with a corresponding orthogonal array or pattern of loudspeakers 22 or 22a in the listening space surrounding a listener 23.
  • the microphones 20a are arranged to receive sounds from, and the speakers 220 are arranged to reproduce sounds from. locations at the left front (LF), right front (RF), right back (RB), and left back (LB) portions of the program and listening spaces, respectively, while in FIG. I the locations 20 and 22 are at front (F), right (R), back (B) and left (L).
  • Encoders or matrixers 24 and 24a produce two transmission signals at 26 or 26a which are then decoded or rematrixed at 28 or 280 to produce presentation signals for driving the speakers at the corresponding locations.
  • FIGS. I and 2 represent signalfonnation and processing operations which may be carried out in a manner producing instantaneous reproduction of live program material but more normally involve some form of storage, i.e., recording, of the signals at one or more points in the sequence.
  • some form of storage i.e., recording
  • the two transmission signals are the left and right groovewalls of an ordinary stereo disc recording or the corresponding audio channels of a stereo broadcast; it is of course the twochannel limits presently imposed by these media which creates the greatest necessity for encoding and decoding, rather than direct transmission in discrete channels.
  • the matrixing or coding of the present invention is advantageously employed in even a simple fixedposition system such as that of FIG. I or FIG. 2 because of the directional symmetry which the invention affords.
  • a further advantage of the present matrixing method and apparatus is its breadth of utility.
  • the present matrixing is not only readily adapted to use in the systems of both FIGS. I and 2, but permits decoding for highly satisfactory use of loudspeaker geometries or orientations which are not in any way matched" to the source-signal geometry or orientation.
  • FIG. 3 outputs of the microphone system (or synthesized directional signals representative of sound sources) 200 and encoder 240 of FIG. 2 are reproduced by the decoder 28 and loudspeakers 22 of FIG. 2.
  • the present matrixing or coding and decoding system not only gives excellent reproduction from all angles with such rotated geometries but permits employment of even more diverse source-signal and reproduction geometries, such as the employment of any number of loudspeakers desired by the listener.
  • FIG. 4 illustrates, for identification, certain angular relations employed in the matrixing and re-matrixing or coding and decoding of the invention.
  • the magnitude and phase with which each source signal appears in each presentation signal is determined wholly and solely by the angular relation between the direction or location represented by the source signal and the direction or location of the loudspeaker to which the presentation signal iSql-O be fed.
  • the overall reproduction matrix (the product of the encoding and decoding matrices) is such that the magnitude and phase of each source signal (relative to its original magnitude and phase) in each presentation signal is everywhere a function of only this angular relation. complete directional symmetry is achieved in any system like that of FIGS. 1 to 3.
  • the angle between any given source (actual or synthesized microphone placement) and loudspeaker location may be designated as or. shown in FIG. 4. it will be seen that all values of a are the same in FIG. 1 and FIG. 2, and identical overall matrices for both of these areaccordingly produced by the invention. as later seen. However. the encoding matrices at 24 and 24a in the respective Figures are not numerically the same but are desirable selected in a manner preserving stereo compatibility, i.e., capability of stereo reproduction on equipment having no decoder. This is done.
  • the laterally neutral reference position is considered the front position and angles are measured clockwise; but references herein to left, rightfand similar terminology will be understood to be used for convenience of expression rather than specific limitation. the effects of reversals. etc., being obvious.
  • a universal encoding matrix for forming two transmission signals T and T from any number. n, of sources is:
  • the phasor coefiicients of the respective transmission signals T, and T are shown in FIG. 5 for the par ticulaif source positions previously discussed. Signals from i.e., to appear to be from" upon reproduction) the left, L. are reproduced in full amplitude and original phase in the T signal, but are zero in the T signal, and vice versa. The signals from other bearingangles appear in both transmission signals but always in quadrature'phase relation, one leading and one lagging the reference phase, which is preserved in the L and R signals. The magnitude of each component is diminished with increase of its relative phase angle (positive or negative), reaching zero at each 90 phase angle 180 difference in source location).
  • Fixed circuits for producing the desired mixing for one or both of these fixed microphone placements may be constructed if so desired. with or without employment of microphone directional patterns. Additional insertion of signal material may then be made to simulate performance at any location by. employment of additonal mixers such as shown in the Schematic diagram of HG. 6.
  • the input signal S is fed to a phase splitter 30 which produces a positive and a negative reference-phase signal and a positive and a negative 90 phase-shifted signal.
  • the reference signal and the phase-shifted signals are attenuated (and reversed in polarity were appropriate) in sine and cosine potentiomcters 32 and 34 set to the bearing angle at which the signal S is to be simulatively inserted.
  • the positive reference signal and the potentiometer outputs are mixed in summers 36 and 38, the outputs of which are then inserted as components of the signals T and T respectively, in accordance with the basic encoding equations earlier stated.
  • each of the signals 5,, S etc. is fed to a polarity splitter (phase inverter) 40.
  • the positive or inphase and negative or opposite-phase signal are fed to a sine-cosine potentiometer producing positive and negative signals of amplitude and polarity determined by the angle of potentiometer setting.
  • the unattenu ated positive signals and the negative sine signals (which are of course in positive phase for angles having negative sine values) from all sources are mixed in a summer 44.
  • the positive cosine-amplitude signals (negative in phase for angles having negative cosine values) are mixed in a summer 46.
  • the output of the latter is advanced in phase by 90 at 48 with respect to the output of the summer 44 and the two are mixed or summed at 50 to form the signal T (As will be recognized by those skilled in the art, the output of the summer 44 must be fed to the summer 50 through a reference-phase portion 52 of the phase shifter 48, the phase-shift of presently available frequencyindepcndent phase-shifters being the difference in phase between the phase-shifted output and the output of a reference-phase channel such as shown at 52, rather than the phase difference between output and input.)
  • orthogonally positioned dipole microphones may be employed to produce directly the signals attenuated in accordance with the sine and cosine of the azimuthal angle of the incident sound sources, with a closely adjacent signal omnidirectional microphone employed to produce the unity or unattenuated components.
  • the transmission signals T and T may either be recorded on any conventional medium. notably a stereo disc or tape recording, or used for instantaneous reproduction, as in quadrasionic FM broadcasting employing the two audio channels provided for ordinary stereo.
  • each presentation signal P is formed from the transmission signals by mixing in the amplitude and phase relation where d),- is the bearing angle between the presentation location and a laterally central reference location and j is the square root l.
  • each presentation signal is formed by multiplying each transmission signal by the complex conjugate of the multiplier or coefficient used (or which would have been used) in inserting signal from the bearing angle in forming the transmission signal, and the resulting respective products are then added.
  • Each resultant presentation signal P,- is thus:
  • the presentation signal P for a speaker at the left postiion is thus the signal T as illustrated in FIG. 5, unaltered, and T R is likewise presented unaltered in forming a presentation signal for a speaker at R (if there is one).
  • Presentation signals for other positions are exactly the same in appearance of phasor diagrams, except that the locations represented are intermediate between the l relation shown in FIG. 5 for the L and R signals. Except for a source signal diametrically opposite the presentation point, all source signals appear in every presentation signal, but with a magnitude which varies continuously from maximum to zero as a function of magnitude of the angle between the signal source direction and the presentation direction.
  • Playback equipment permitting sesetion of an individual speaker location at any desired angle whatever may be devised along the same lines as the signalpreparation equipment earlier described.
  • provision is in general superfluous, since practical speaker placements are not nearly as diverse as micro phone placements, in which balance as between front and back, right and left, etc., is optional rather than a requirement.
  • the fixed presentation-signal outputs for the eight positions illustrated suffice to cover the needs and preferences of users of four-speaker systems, while interals of 15 are wholly adequate for virtually any practical use.
  • FIG. 8 There is shown in FIG. 8 one construction for a decoder which may be employed with a very wide variety of speaker geometries.
  • the respective transmission signals T, and T are fed to 90 phase shifters 70 and 72, each of which has positive and negative referencephase and phase-shifted outputs.
  • These outputs are fed to a fixed mixing network 74 consisting of voltagedividers attenuating the input signals and distributing the signals so attanuated to summers producing outputs in accordance with equation (2).
  • Fixed output terminals 76 are provided for presentation through suitable amplifiers by loud-speakers at any selected multiple of l intervals (or any other intervals for which outputs are provided). The number and placement of speakers may thus be selected in accordance with the preference (including economic limitations) of the user.
  • the speakers are normally preferred to be equally spaced in bearing-angle and equidistant from the listening position, i.e., disposed in the form of a square or regular polygon.
  • the listening position i.e., disposed in the form of a square or regular polygon.
  • room shape and acoustics and personal preferences may result in other arrangements in many cases.
  • FIG. 9 Another form of decoder with selectable fixedlocation output terminals is shown in FIG. 9.
  • the transmission signals T and T are fed to a sum and difference circuit 80 to produce a sum signal T; and a difference signal T
  • the difference signal is treated in the same manner as at 70 or 72 of FIG. 8, the separate phase-shifter channels for the reference phase 82 and the shifted phase 84 being again shown in FIG. 9.
  • the respective polarities of the reference and phase-shifted difference signal TA are fed to fixed voltage dividers at 86 and 88 and the attenuated outputs are fed to summers 90 along with the sum signal T; from the reference-phase channel 91 producing output presentation signals for the pre-selected angles 4),, (11 etc., for which the taps on the attenuators or dividers 86 and 88 are designed.
  • the transmission signal pair T and T contains exactly the same information as the transmission signal pair T and T and these signal sets are readily convertible from one form of the other in either direction without any alteration-of the available informataion content. Although these two forms of the same signal information are normally the most useful and simplest in equipment implementation, other transmission signal pairs identical in overall information content and ready convertibility to and from these specific forms may be devised and will be understood to be included in the expressions above.
  • individual presentation signals may,
  • auxiliary signal treatment of the same type heretofore employed with other coding and decoding systems, such as varying the amplification of amplifiers feeding particular loud-speakers to increase apparent contract" or sound-source localization for certain types of sounds.
  • the encoded transmission signals are readily useable with existing reproduction equipment having no provision for decoding of multidirectional signals.
  • the sum of the two transmission signals is the simple sum of all of the source signals in their original phase.
  • employment of the transmission signals in the sum-and-difference mono-compatible matrixing of stereo FM broadcasting, or reproduction of an encoded stereo disc recording on a monaural phonograph produces perfect monaural reproduction.
  • the employement of the two encoded channels as the left and right channels of conventional stereo reproduction produces only slightly less apparent left-right separation than a conventional stereo recording (as in prior systems for quadrasonic encoding and decoding with two-channel transmission).
  • the decoder may be made for artificially encoding ordinary stereo signals containing no directional information, so that such program material is reproduced in the multidirectional speaker system in a manner generally resembling the reproduction of signals wherein the further directional information is encoded.
  • Ordinary stereo signals correspond to source signals at left front, LF, and right front, RF.
  • FIG. 10 an adapter which may be substituted for the sum and difference circuit 80of FIG. 9, for example by a switch on the decoder, to produce a listener effect or sensation similar to that of direction-encoded signals having source-signal components only from these directions.
  • the ordinary stereo signals are fed to respective 45 phase splitters 92 and 94 to produce a sum signal T I in reference phase and a difference signal T A in quadrature phase.
  • the selection of the two transmission signals for direct reproduction at L and R locations, respectively is of significance only for compatibility with conventional stereo equipment having no decording provision.
  • the invention may be employed in applications wherein stereo compatibility is unimportant.
  • the invention may be used for the sole purpose of conserving tape space, and thus extending playing time, in the general type of recording now done in four or more discrete tape channels. By compressing the information into two recording channels and then expanding in playback, much greater utilization of tape space is made.
  • the reference direction of the bearing-angles used in encording may be chosen more or less arbitrarily, and the directions represented by the two transmission signals are accordingly equally arbitrary, so long as they are selected in diametric opposition.
  • a primary use for a larger number of channels is to sharpen the directionality pattern for any given speaker array, i.e., to reduce the cross-talk which is an unavoidable consequence of employment of a number of loudspeakers larger than the number of transmission channels.
  • the invention in these further aspects has great advantage even where the number of transmission channels is equal to or greater than the number of required presentation signals, not only for the purpose of permitting rotation of presentation signals, such as in reproduction of a four-track tape recording recorded for 2 plus-2 loudspeaker presentation on loudspeakers arranged in a 1-2-1 orientation, but for other purposes later seen.
  • the relative importance of these three factors in producing the illusion of presence at the actual performance is a psychoacoustic matter which is presently incapable of quantitative evaluation. It has been experimentally established that the reproduction produced by the two-channel matrixing of the above-described embodiments is more satisfactory than with other matrices for the same purpose.
  • the performance may be described in terms of the factors of merit above by the following: The pattern demonstrates a complete null at l, an amplitude reduction of 3 dB at (and of course 270, these being a convenient point of reference for measuring pattern sharpness), and no component is presented with a phase difference of as great as l80 from any other, any components which are reproduced with a difference of phase approaching 90 from their original relative phase being essentially negligible in amplitude.
  • Three-channel (and further multiple-channel) systems of the first type mentioned above may be described as compatible with the two-channel system.
  • One current utility of such embodiments of the invention is in the production of three-track or four-track tape recordings which may be played back, with suitable decoding, with any desired multiple array of speakers or may, alternatively, be played back as ordinary stereo recordings by equipment which cannot utilize the auxilary recorded channel or channels.
  • Even greater utility lies in the substantial advantages which the invention possesses in making it practical to incorporate quadrasonic signals which are effectively wholly discrete in reproduction in media such as FM broadcasting and disc recording.
  • each auxiliary channel is of course such as to maintain the above-described essential characteristics of the overall transmission or presentation function.
  • each of the auxiliary transmission signals in order to do this, it is necessary that the encoding and decoding of each of the auxiliary transmission signals produce an added component for the presentation signal which is itself a function solely of the difference angle having a maximum value at zero difference angle.
  • the simplest and most desirable manner of utilizing additional channels is to employ an encoding function of 6 for production of each auxiliary transmission signal which, when multiplied by the conjugate decoding function of d) itself produces a product which is a single-variable function of the difference angle and which, when added to the presentation signal function which results from the two-channel transmission, increases the sharpness of the amplitude maximum in the pattern.
  • the auxiliary signal T thus formed may be employed with either the T and T transmission signals of equations (1) or the transmission signals T 2 and T A of (4) above.
  • the overall playback function thus obtained,
  • This overall reproduction function produces presentation signals free of phases shifts and with a null at 180, the magnitude at 90 being down 6 dB from the maximum at 0.
  • the same result is of course obtained with appropriate partial blending of the T and T signals previously described, and the same attenuation of T
  • the recorded or broadcast sets of transmission signals will not normally include this alteration.
  • the modified set of transmission signals is preferably generated in the decoder from the unmodified signals as recorded or broadcast.
  • m is the square of the attenuation factor used in forming the modified T and T Appreciable variation in details of reproduction characteristics is obtained by selection of m.
  • m is varied in the range from 0.5 to 1.0, the backlobe earlier mentioned is reintroduced, but the 90 separation" is simultaneously improved as indicated numerically earlier.
  • m having an intermediate value of 0.707, the 90 separation is 7.66 dB and the backlobe level is 28.3 dB below the 0 maximum.
  • the choiceof the constant m thus involves a tradeoff of desirable pattern characteristics which is incapable of evaluation as regards psychoacoustic effectiveness to the listener, and the threechannel decoder is desirably provided with means for adjustment by the user of the factor m above defined within the range of 0.5 to 1.0.
  • the factor V711 is introduced into the transmission signals at the decoder, and the conjugate functions thereupon immediately applied for decoding, the latter also of course including the factor V m
  • the two successive attenuations by the factor, ⁇ [Fi may be replaced by a single attenuation by the factor m, as by ganged attenuator potentiometers atzthe imputs for the unmodified T and T signals, whereby the user may select a value of m between 0.5 and 1.0.
  • the same general principle may be employed in further adding a fourth channel for still further increasing the contrast between the amplitude of reproduction of a source signal from a loudspeaker in a position corresponding to the original position of the source and the amplitude of its reproduction from other loudspeakers,
  • phase relations of the source-signal components in each presentation signal are the same as in the twochannel case, except in a relatively minor respect to be later mentioned.
  • 90 separation is vastly improved, as now seen.
  • the manner of inserting the factor m does not affect the two basic transmission channels, so that it may be inserted either in the encoding equipment, the decoding equipment, or a combination of both.
  • the factors involved in selection of m by the listener are generally similar to those in the three-channel case, and the listener may be provided with adjustment of this factor in the range of 0.33 to 1.0 if so desired.
  • T and T are transmitted without the m-factor attenuation, attenuated just prior to the decoding, and thereupon decoded by employing the conjugate-function rematrixing already described.
  • an even more advantageous utilization of the effects produced by variation of the factor min (7) above may be made in connection with reducing the frequency-range requirement of the two auxiliary channels, without impairment of the reproduction.
  • FIG. 1 1 An overall system of encoding, transmission, and decoding employing the fourchannel matrixing of the invention, with input signal sources designated S 0 S 0 etc. and output or presentation signals designated P ,1 P 4, etc., each input signal and each output signal being identified with an azimuthal direction.
  • the azimuthal angles are in this instance measured counterclockwise from a reference direction at the right of the listener, thus including the 1r/2 angle additive appearing in the forms of expression heretofore used herein for simplicity of demonstration of th actual right-left symmetry inherently possessed by the matrix.
  • all of the signal sources are merely additively mixed without phase alteration.
  • each source signal is phase-shifted to produce, for each of its frequency components, a phase lag with respect to the corresponding T; component equal to the source azimuthal angle (whether actual or synthetic) and with unaltered amplitude.
  • the T auxiliary channel is formed identically with the T A channel, except that the direction of phase-shift is reversed.
  • the T channel is formed in the same manner as the T or T except that each phase shift angle is doubled.
  • the T and T signals Prior to transmission, are band-pass filtered to limit their content by limitation to mid-range frequencies. such asfrorn 130 Hz to 3kHz.
  • phase equalizers are employed for the T and T2 channels to maintain the desired phase relations in the signals are transmitted.
  • transmitted will of course be understood to include the various forms of recording or signal-storage employed for later reproduction, such as phonograph records and tapes, as well as the instantaneous transmission employed in such media as FM broadcasting.
  • the basic signal pairs T and T or T; and T incorporate each sound-source signal in a reference phase and an azimuth-identifying phase differing from the reference phase by a phaseangle equal to the azimuthal angle of the sound source.
  • T and T where one channel carries only the referencephase component and the other carries only the azimuthidentifying component.
  • the other form of the transmission pair carries exactly the same signal information, however, although linear operations are required to separate these distinct signal components.
  • the third channel T- incorporates each signal in a relative phase equal but opposite to the azimuth-identifying phase and the fourth signal T is formed in the same manner as T A or T except that the phase differs from the reference phase by a doubled phase-angle for the corresponding signal source.
  • the generalized showing of FIG. 11 is of course applicable to radio broadcasting, recording, or any other audio reproduction medium. It is of particular advantage where required transmission bandwidth is a problem, since the limited frequency range of the auxiliary channels permits reduced bandwidth requirement as compared with quadrasonic systems wherein the same four transmission channels are each used for the pre sentation signal at a location assigned to that channel.
  • the utility of the four encoded chanels in various recording and FM transmission schemes which have heretofore been proposed for the latter type of transmission is obvious, and it will be understood that the showing in the drawing of direct feeding of the transmission channels to the decoding portion is highly schematic, the direct connections shown normally representing production and reproduction of a recording or FM broadcast employing multiplex provision for the auxiliary channels. (As will be evident, the channels T and T of FIG. 11 will normally be replaced by T and T in recording equipment for which this form is more appropriate.)
  • the two basic channels are transmitted as the sum and difference signals of conventional mono-compatible stero broadcasting.
  • the auxiliary signals are alternated at a sampling frequency of 9.5 kHz and multiplexed together, as a composite modulation of the quadrature-phased 38-kI-lz carrier known in the art for speaker-identified quadraplex FM transmission, but heretofore objectionable because of bandwidth requirement.
  • the four channels (using T and T as the basic stero channels) are substituted for speaker-identified channels in the four-channel disc reproducing system described at Volume 19, page 576, of the Journal of the Audio Engineering Society.
  • each of the four transmission channels in the decoding equipment associated with an FM receiver, for example
  • each presentation signal is conjugate to the treatment by which that transmission channel was produced, except that the angles of phase-shift correspond to the locations of the loudspeakers, rather than the sound sources.
  • the T signal is again unaltered in phase and continues to serve as a reference phase, its suitability for this purpose again being maintained by reference phase shifts required by the operation of the frequencyindependent phase shifters employed for the other channels.
  • the altered outputs of the four transmission channels are all in phase and directly additive. 7
  • each presentation signal is passed through an amplitude equalizer or band-attenuating filter which is generally complementary to the band pass filters used in the auxiliary channel signal formation except for the attenuation magnitude.
  • each equalizer attenuates the signal by 3 dB, and compensation for the power contribution of the auxiliary channels is similarly made in the adjoining upper and lower roll-off portions of the pass band of the filters used in transmission. Sharpness of the band-pass filter characteristics and corresponding equalization filter characteristics is not required, for reasons later to be mentioned.
  • Numerical values of the encoding matrix, the decoding matrix, and the overall playback matrix are shown in FIG. 12 for the conditions corresponding to those heretofore used in conventional four-track reproduction, which identifies each transmission channel with a specific loudspeaker of the 2 plus 2 speaker array.
  • the encoding and decoding matrices are shown with the matrix elements separated in this respect.
  • the overall playback matrix is shown in an unsimplified form from which most of the terms vanish upon expension, as will be seen upon study.
  • the signal frequencies which are unattenuated in T and T appear only in a single loudspeaker because the other three speakers are in each case at the nulls previously mentioned. Since all presentation signals of this type are of the reference phase, the reproduction of these frequencies is exactly the same as in the case of direct transmission of each loudspeaker signal from the corresponding sound source.
  • FIG. 12 shows, in polar dia gram form, the amplitudes and phase angles of repro- 6 duction for the four-channel and two-channel systems 5 as a function of the angle between each speaker location and the sound-source location portrayed.
  • the Figure shows, in dotted form, the amlitude of reproduction of a typical transitional" frequency component, i.e., a frequency component in the partialattenuation (and subsequent relative boost) or roll-off region, corresponding to one intermediate or fractional value of m.
  • a typical transitional frequency component i.e., a frequency component in the partialattenuation (and subsequent relative boost) or roll-off region, corresponding to one intermediate or fractional value of m.
  • the principles of the invention may be further extended to still higher numbers of channels while preserving the two basic transmission signals T and T or T and T for reproduction on equipment not capable of using the auxiliary channels.
  • auxiliary channels for the two-channel system first described herein, which may be considered as compatible additions to the basic two-channel system
  • the principles of the invention' may be employed for multiple channels which are all associated with particular bearing angles in the same general manner as the signals T and T are identified with the directions left and right, i.e., the signals may be played back directly or decoded for other speaker positions.
  • the decoding function f (45') for each transmission channel in forming each presentation signal may be stated as where d) is the bearing angle of the presentation signal with reference to the direction to which the transmission signal corresponds.
  • the overall or summed presentation signal function is of course not affected by this alteration of reference point used in the encoding and decoding, being the same as the encoding function except for the difference-angle argument.
  • Similar encoding functions (and conjugate decoding functions) may be employed for larger numbers of transmission signals corresponding to equallyspaced directional angles. For three channels, at 120 intervals, the encoding function is and the decoding function of (1) is identical (the function having no imaginary term).
  • the overall presentation signal function is again identical with the encoding function except for the difference-angle argument.
  • Such encoding may of course be used in the making of discrete-signal four-track recordings which can be played back with any desired speaker array, or the presentation signals may be recorded for the improved image-localization of ordinary discrete-channel playback equipment discussed above in connection with FIG. 1 1, or for other purposes which do not require the monaural and stero compatibility of the forms of the invention earlier described.
  • a method of producing signals with directional audio information comprising matrixing source signals representative of sounds from different bearing angles 0, each measured from a source reference direction, to form at least three transmission signals, T2 T and T capable of being re-matrixed for production of presentation signals, each of said transmission signalshaw ing encoding mixing coefficients substantially corresponding to values of single-variable 360 repetitive functions of said bearing angles 6, said single-variable functions being defined as:
  • T T A and 2 SM jflh-l-rr/Z) T are respectively given by T T and T defined as:
  • Th h d f l i 8 comprising hifti h 18.
  • said three muphase of said other transmission signals in amounts wally independent lineal COmbinatiOfls Of equal in frequency characteristic to the phase shifts and TT are respectively given by T1,, TR and Tr 16- produced by said filters. fined 381 10.
  • a recording with directional audio information derived from matrixed source signals representative of sounds from different bearing angles 6, each measured (T: ()T,- T 5: S u from a source reference direction, to form at least three 2 2 2 recorded signals, T: T and T each having mixing l TA+ OTT) 1 TA): 1 2 5k j(6l-+1r/2 coefficients substantially corresponding to values of 2 2 2 k I single-variable 360 repetitive functions of said bearing 1 4- 7 l' m;+ 2) angles 6, said single-variable functions being defined as: 3 (OT-+0T+ 2 J 19.
  • said method comprises the steps of multiplying each of the transmission signals T T and T by decoding mixing coefficients and adding the product signals formed thereby substantially in accordance with the relationship defined by /2) i I12) 21.
  • S in the k-th source signal, 6, is the bearing angle between the sound location thereby represented and said source reference direction andj is the square root of -l said method comprising the steps of multiplying each of said transmission signals by decoding mixing coefficients and adding the product signals formed thereby substantially in accordance with the relationship defined by where P,- is the presentation signal for the transducer located at the bearing angle 6; measured to the reference direction at a laterally central location as to the listening space.
  • said method comprises the steps of multiplying each of the signals T T T and T by decoding mixing coefficients and adding the product signals formed thereby substantially in accordance with the relationship defined by 23.
  • the method of claim 19 wherein the signal T has a substantially narrower frequency range than T and T and each presentation signal is attenuated in the frequency range of these signals to equalize the overall frequency response.
  • Apparatus for the production of signals with directional audio information comprising matrix means for matrixing source signals representative of sounds from different bearing angles 0, each measured from a source reference direction, to form at least three transmission signals, T T A and T-,, capable of being rematrixed for production of presentation signals, said matrix means including means for providing encoding mixing coefficients for each of said transmission signals substantially corresponding to values of single-variable 360 repetitive functions of said bearing angles 0, said single-variable functions being defined as:
  • S is the k-th source signal
  • 6 is the bearing angle between the sound location thereby represented and said source reference direction
  • j is the square root of -1.

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US288873A 1971-10-06 1972-09-13 Signal matrixing for directional reproduction of sound Expired - Lifetime US3906156A (en)

Priority Applications (17)

Application Number Priority Date Filing Date Title
US288873A US3906156A (en) 1971-10-06 1972-09-13 Signal matrixing for directional reproduction of sound
CA153,095A CA997277A (en) 1971-10-06 1972-10-03 Signal matrixing for directional reproduction of sound
GB1343875A GB1411995A (en) 1971-10-06 1972-10-03 Signal matrixing for directional reproduction of sound
GB4555872A GB1411994A (en) 1971-10-06 1972-10-03 Signal matrixing for directional reproduction of sound
FR7235624A FR2156168B1 (de) 1971-10-06 1972-10-06
DE2249039A DE2249039C2 (de) 1971-10-06 1972-10-06 Verfahren zur Aufnahme und Wiedergabe von richtungsbezogener Schallinformation
JP48102583A JPS582520B2 (ja) 1972-09-13 1973-09-11 ホウコウセイオ−デイオジヨウホウノ サイセイホウホウ
US05/468,238 US3985978A (en) 1971-10-06 1974-05-09 Method and apparatus for control of FM beat distortion
US05/468,279 US3946165A (en) 1971-10-06 1974-05-09 Method and apparatus for control of crosstalk in multiple frequency recording
US05/578,078 US3970788A (en) 1971-10-06 1975-05-16 Monaural and stereo compatible multidirectional sound matrixing
CA252,643A CA1006829A (en) 1971-10-06 1976-05-17 Signal matrixing for directional reproduction of sound
CA252,645A CA1006831A (en) 1971-10-06 1976-05-17 Signal matrixing for directional reproduction of sound
CA252,647A CA1006824A (en) 1971-10-06 1976-05-17 Signal matrixing for directional reproduction of sound
CA252,644A CA1006830A (en) 1971-10-06 1976-05-17 Signal matrixing for directional reproduction of sound
CA252,646A CA1006832A (en) 1971-10-06 1976-05-17 Signal matrixing for directional reproduction of sound
CA252,648A CA1006828A (en) 1971-10-06 1976-05-17 Signal matrixing for directional reproduction of sound
US05/836,507 US4152542A (en) 1971-10-06 1977-09-26 Multichannel matrix logic and encoding systems

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US00187065A US3856992A (en) 1971-10-06 1971-10-06 Multidirectional sound reproduction
US288873A US3906156A (en) 1971-10-06 1972-09-13 Signal matrixing for directional reproduction of sound

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US05/468,279 Continuation-In-Part US3946165A (en) 1971-10-06 1974-05-09 Method and apparatus for control of crosstalk in multiple frequency recording
US05/468,238 Continuation-In-Part US3985978A (en) 1971-10-06 1974-05-09 Method and apparatus for control of FM beat distortion
US05/578,078 Division US3970788A (en) 1971-10-06 1975-05-16 Monaural and stereo compatible multidirectional sound matrixing
US05/578,078 Continuation-In-Part US3970788A (en) 1971-10-06 1975-05-16 Monaural and stereo compatible multidirectional sound matrixing
US05/701,228 Continuation-In-Part US4085291A (en) 1971-10-06 1976-06-30 Synthetic supplementary channel matrix decoding systems
US05/836,507 Continuation-In-Part US4152542A (en) 1971-10-06 1977-09-26 Multichannel matrix logic and encoding systems

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2711299A1 (de) * 1976-03-15 1977-09-22 Nat Res Dev Tonwiedergabesystem
US4085291A (en) * 1971-10-06 1978-04-18 Cooper Duane H Synthetic supplementary channel matrix decoding systems
US4119798A (en) * 1975-09-04 1978-10-10 Victor Company Of Japan, Limited Binaural multi-channel stereophony
US4139729A (en) * 1976-07-01 1979-02-13 National Research Development Corporation Sound reproduction system with matrixing of power amplifier outputs
US5708719A (en) * 1995-09-07 1998-01-13 Rep Investment Limited Liability Company In-home theater surround sound speaker system
US5930370A (en) * 1995-09-07 1999-07-27 Rep Investment Limited Liability In-home theater surround sound speaker system
US6118876A (en) * 1995-09-07 2000-09-12 Rep Investment Limited Liability Company Surround sound speaker system for improved spatial effects
US20040033795A1 (en) * 2000-02-04 2004-02-19 Walsh Patrick J. Location information system for a wireless communication device and method therefor
US20100145486A1 (en) * 2008-12-10 2010-06-10 Sheets Laurence L Method and System for Performing Audio Signal Processing
EP2476118A1 (de) * 2009-09-11 2012-07-18 Barry Stephen Goldfarb Phasenschichtungsvorrichtung und verfahren für ein komplettes audiosignal
CN106067996A (zh) * 2015-04-24 2016-11-02 松下知识产权经营株式会社 语音再现方法、语音对话装置

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5521519B2 (de) * 1973-05-10 1980-06-10
JPS5247884B2 (de) * 1973-05-10 1977-12-06
NL185876C (nl) * 1973-05-10 1990-08-01 Nippon Columbia Stelsel voor registratie vanuit een aantal richtingen afkomstige geluidssignalen op een registratiemedium en stelsel voor weergave van dergelijke signalen.
GB1494751A (en) * 1974-03-26 1977-12-14 Nat Res Dev Sound reproduction systems

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3679832A (en) * 1971-03-23 1972-07-25 Bell Telephone Labor Inc Three-channel fm stereo transmission
US3686471A (en) * 1969-11-28 1972-08-22 Victor Company Of Japan System for recording and/or reproducing four channel signals on a record disc
US3708623A (en) * 1970-04-29 1973-01-02 Quadracast Syst Inc Compatible four channel fm system
US3754099A (en) * 1970-11-09 1973-08-21 Pioneer Electronic Corp Four channel stereophonic broadcasting system
US3761628A (en) * 1972-04-13 1973-09-25 Columbia Broadcasting Syst Inc Stereo-quadraphonic matrix system with matrix or discrete sound reproduction capability

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1359509A (en) 1970-06-15 1974-07-10 Scheiber P Decoder apparatus for use in a multidirectional sound system
GB1369813A (en) 1971-02-02 1974-10-09 Nat Res Dev Reproduction of sound
US3745252A (en) 1971-02-03 1973-07-10 Columbia Broadcasting Syst Inc Matrixes and decoders for quadruphonic records

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3686471A (en) * 1969-11-28 1972-08-22 Victor Company Of Japan System for recording and/or reproducing four channel signals on a record disc
US3708623A (en) * 1970-04-29 1973-01-02 Quadracast Syst Inc Compatible four channel fm system
US3754099A (en) * 1970-11-09 1973-08-21 Pioneer Electronic Corp Four channel stereophonic broadcasting system
US3679832A (en) * 1971-03-23 1972-07-25 Bell Telephone Labor Inc Three-channel fm stereo transmission
US3761628A (en) * 1972-04-13 1973-09-25 Columbia Broadcasting Syst Inc Stereo-quadraphonic matrix system with matrix or discrete sound reproduction capability

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4085291A (en) * 1971-10-06 1978-04-18 Cooper Duane H Synthetic supplementary channel matrix decoding systems
US4119798A (en) * 1975-09-04 1978-10-10 Victor Company Of Japan, Limited Binaural multi-channel stereophony
DE2711299A1 (de) * 1976-03-15 1977-09-22 Nat Res Dev Tonwiedergabesystem
FR2345047A1 (fr) * 1976-03-15 1977-10-14 Nat Res Dev Systemes de reproduction des sons
US4095049A (en) * 1976-03-15 1978-06-13 National Research Development Corporation Non-rotationally-symmetric surround-sound encoding system
US4139729A (en) * 1976-07-01 1979-02-13 National Research Development Corporation Sound reproduction system with matrixing of power amplifier outputs
US6118876A (en) * 1995-09-07 2000-09-12 Rep Investment Limited Liability Company Surround sound speaker system for improved spatial effects
US5930370A (en) * 1995-09-07 1999-07-27 Rep Investment Limited Liability In-home theater surround sound speaker system
US5708719A (en) * 1995-09-07 1998-01-13 Rep Investment Limited Liability Company In-home theater surround sound speaker system
US20040033795A1 (en) * 2000-02-04 2004-02-19 Walsh Patrick J. Location information system for a wireless communication device and method therefor
US20100145486A1 (en) * 2008-12-10 2010-06-10 Sheets Laurence L Method and System for Performing Audio Signal Processing
US8320584B2 (en) 2008-12-10 2012-11-27 Sheets Laurence L Method and system for performing audio signal processing
EP2476118A1 (de) * 2009-09-11 2012-07-18 Barry Stephen Goldfarb Phasenschichtungsvorrichtung und verfahren für ein komplettes audiosignal
EP2476118A4 (de) * 2009-09-11 2014-08-13 Barry Stephen Goldfarb Phasenschichtungsvorrichtung und verfahren für ein komplettes audiosignal
CN106067996A (zh) * 2015-04-24 2016-11-02 松下知识产权经营株式会社 语音再现方法、语音对话装置
CN106067996B (zh) * 2015-04-24 2019-09-17 松下知识产权经营株式会社 语音再现方法、语音对话装置

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GB1411994A (en) 1975-10-29
FR2156168B1 (de) 1980-04-18
FR2156168A1 (de) 1973-05-25
DE2249039C2 (de) 1986-07-17
CA997277A (en) 1976-09-21
DE2249039A1 (de) 1973-04-12

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