US3856992A - Multidirectional sound reproduction - Google Patents

Multidirectional sound reproduction Download PDF

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US3856992A
US3856992A US00187065A US18706571A US3856992A US 3856992 A US3856992 A US 3856992A US 00187065 A US00187065 A US 00187065A US 18706571 A US18706571 A US 18706571A US 3856992 A US3856992 A US 3856992A
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signals
presentation
signal
source
function
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D Cooper
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Priority to US00187065A priority Critical patent/US3856992A/en
Priority to US288873A priority patent/US3906156A/en
Priority to GB4555872A priority patent/GB1411994A/en
Priority to CA153,095A priority patent/CA997277A/en
Priority to GB1343875A priority patent/GB1411995A/en
Priority to FR7235624A priority patent/FR2156168B1/fr
Priority to JP47100548A priority patent/JPS582519B2/ja
Priority to DE2249039A priority patent/DE2249039C2/de
Priority to US05/468,238 priority patent/US3985978A/en
Priority to US05/468,279 priority patent/US3946165A/en
Publication of US3856992A publication Critical patent/US3856992A/en
Application granted granted Critical
Priority to US05/578,078 priority patent/US3970788A/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 CA252,645A priority patent/CA1006831A/en
Priority to CA252,644A priority patent/CA1006830A/en
Priority to CA252,646A priority patent/CA1006832A/en
Priority to US05/701,228 priority patent/US4085291A/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

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  • I ABSTRACT Multidirectional audio sound signals are encoded in transmission signals employingphasor matrixing coefficients varying in amplitude and phase as a continuous function of the bearing angle or direction Of each signal source.
  • the transmission signals are decoded to provide presentation signals for loudspeaker placement patterns which maybe selected by the listener.
  • 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.
  • a present requirement for widespread adoption of any quadrasonic system is that of compatibility with continued use of existing reproducing equipment, monaural and stereo. Stated otherwise, it is generally recognized that recordings made for quadrasonic reproduction are desirably capable of satisfactory reproduction by monaural record-players and conventional stereo record-players, and quadrasonic FM transmissions (whether live or from recordings) must similarly be reproduced as monaural or stereo material by existing receivers.
  • 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 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 systems afford.
  • anomalies or directional ambiquities 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 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 l2-l i.e., at opposite sides of the listener and at the center front and back.
  • the required speaker orientation is specified in connection with the directions represented by the four discrete transmission channels or with the coding used in the two-channel transmission or recording, and no manner is provided, so far as is known, for using different speaker orientations, or a different number of speakers, while retaining satisfactory reproduction.
  • 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 l-2l 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 principles of the invention may also be employed to provide analogous flexibility in reproduction of signals transmitted in more than two channels.
  • the invention accordingly provides decoders producing readily selectable presentation signals for the with respect to the listener.
  • a pair of number and pattern of the array of loudspeakers preferred by the listener, as well as equipment whereby encoding of multi-directional sound into a plurality of channels, and selection of directional effects may be simply performed by a recording studio or record manufacturer or broadcaster without limitation to expected use by only those listeners having a specific loudspeaker arrangement.
  • the universal or rotatable aspect of the relation between encoding and decoding of the transmission signals of the invention is obtained by the employment of mixing coefficients which alter both the phase and amplitude of each source signal, in encoding, and of each transmission signal, in decoding, in a manner producing an overall reproduction matrix wherein the phase and amplitude of appearance of any source-signal in any presentation signal is entirely a function of the angular relation between the azimuthal location of the source and the azimuthal location of the speaker for which the presentation signal is formed, i.e., of the difference in bearing angles of the source and the reproducing loudspeaker.
  • FIG. 1 is a schematic illustration of one type of quadrasonic sound 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 Figures 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. 10 is a block diagram of an adapter circuit for employing the decoder of FIG. 9 with conventional stereo signals.
  • FIGS. 1 through 3 there are shown basic forms of quadrasonic sound systems which may advantageously employ the invention.
  • FIGS. 1 and 2 show systems which are, except for the matrices for 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. 1 and 2 are alternate forms of quadrasonic systems heretofore employed with various matrixing systems.
  • an array or pattern of orthogonal microphones 20 or 20a 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 22a 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. 1 the locations 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 260 which are then decoded or rematrixed at 28 or 28a to produce presentation signals for driving the speakers at the corresponding locations.
  • FIGS. 1 and 2 represent signalformation 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.
  • the two transmission signals are the left and right groove-walls of an ordinary disc recording or the corresponding audio channels of a stereo broadcast; it is of course the two-channel 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. 1 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. 1 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 One example of such an overall system is shown in FIG. 3, where outputs of the microphone system (or synthesized directional signals representative of sound sources) 20a and encoder 24a 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 is to 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 sound source (actual or synthesized microphone placement) and loudspeaker location may be designated as a, shown in FIG. 4. It will be seen that all values ofa are the same in FIG. 1 and FIG. 2, and identical overall matrices for both of these geometries are accordingly 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 desirably selected in a manner preserving stereo compatibility, i.e., capability of stereo reproduction on equipment having no decoder.
  • the laterally neutral reference position is considered the front position and angles are measured clockwise; but reference herein to left, right, and 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:
  • mixing equations below calculated from the universal matrix above, may be employed for utilizing the invention with fixed four-microphone placements, with or without the addition of other signals such as the on-mic touch-up signals frequently added for solosits and other special effects.
  • numerical values of the mixing equations are:
  • Fixed circuits for producing the desired mixing for one or both 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 additional mixers such as shown in the schematic diagram of FIG. 6.
  • the input signal S is fed to a 90 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 signals and the phase-shifted signals are attenuated (and reversed in polarity where appropriate) in sine and cosine potentiometers 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 8,, 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 unattenuated 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 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 frequencyindependent 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.)
  • microphone sensitivity patterns of well-known types may readily be employed in substitution for the indicated attenuation potentiometer networks of some or all of the signals 8,, S etc., in the signal-mixing system of FIG. 7.
  • 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 single 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 quadrasonic 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 T (l-sin (b j(coS (in) +T (l sin (1), +j cos (2) where d), is the bearing angle between the presentation location and a laterally central reference location and j is the square root of l.
  • each presenation 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 that 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 position is thus the signal T as illustrated in FIG. 5, unaltered, and T 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 l80 relation shown in FIG. 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.
  • N Playback equipment permitting selection 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 microphone 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-speakers systems, while intervals 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 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 attenuated to summers producing outputs in accordance with equation (2).
  • Fixed output terminals 76 are provided for presentation through suitable 5 amplifiers by loudspeakers at any selected multiple of 15 intervals (or any other intervals for which outputs are provided). The number of 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 e and a difference signal T A
  • 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 T A 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 e from the reference-phase channel 91 producing output presentation signals for the pre-selected angles 11),, (1) 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 e and T A and these signal sets are readily convertible from one form to the other in either direction without any alteration of the available information 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 beincluded in the expressions above.
  • individual presentation signals may, after formation, be touched up in accordance with listener preference. For example a particular listener may find the overall effect more pleasing with further phase shifting of one or more of the presentation signals after the formation thereof (not shown).
  • directional effects may be emphasized by auxiliary signal treatment of the same type heretofore employed with other coding and decoding systems, such as varying the amplification of amplifiers feeding particular loudspeakers to increase apparent contrast 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 employment 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. an adapter which may be substituted for the sum and difference circuit 80 of 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 slitters 92 and 94 to produce a sum signal T 6 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 decoding 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 encoding 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 its broader aspects may be employed even where the number of transmission channels is equal to or greater than the number of required presentation signals, 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, as 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 180, an amplitude reduction of 3 dB at 90 (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 180 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.
  • a typical current utility of such embodiments of the invention is in the production of threetrack 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 auxiliary recorded channel or channels.
  • disc recording and broadcasting may be provided with more than two signal channels, such auxiliary signals may likewise be employed in these media for similar purposes.
  • the encoding and decoding of the auxiliary channel must be such as to maintain the abovedescribed essential characteristics of the overall transmission or presentation function.
  • auxiliary transmission signal or signals
  • the simplest and most desirable manner of utilizing a third channel is to employ an encoding function of 6 for production of the third 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 in forming the added component for each presentation signal P produces a product function of the difference in angles which, when added to the basic two-channel presentation function, substantially sharpens the directional effects.
  • the overall presentation signal is P T S;,-[1+2 cos (tin-910l- With this overall playback function, all sound sources are produced in all speakers in their original relative phase, and the amplitude for an angle difference of (or, of course, 270) is about 10 dB less than the maximum at 0.
  • 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 6 and T of (4) above.
  • the overall playback function thus obtained although improving the pattern in the respects just mentioned, produces a signal component at 180 of the same magnitude as the signal component at 90, i.e., about 10 dB from the maximum at 0. This backlobe may be eliminated by a simple alteration.
  • T E and T A form of transmission of
  • the modified set of transmission signals is preferably generated in the decoder from the unmodified signals as recorded or broadcast.
  • the overall transmission or presentation equation set forth above resulting from the modified transmission signals has a coefficient expression shown in brackets which may also be written as This will be seen to be of the same form as the equation (5) coefficient for the unmodified three transmission signals, each overall presentation signal being expressable as where m is the square of the attenuation factor used in forming the modified T A and T Appreciable variation in details of reproduction characteristics is obtained by selection of m. As m is varied in the range from 0.5 to 1.0, the backlobe earlier mentioned is re-introduced, but the 90 separation is simultaneously improved as indicated numerically earlier. With 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 maximum.
  • the choice of 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 V m 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 m
  • the two successive attenuations by the factor m may be replaced by a single attenuation by the factor in, as by ganged attenuator potentiometers at the inputs for the unmodified T A 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, i.e., in further sharpening of the overall presentation signal functions of
  • a fourth channel addition to the three channels described above which meets the criteria already described is the transmission signal T formed as follows:
  • Such a function may be produced by summing the outputs of two quadrupole microphones (each with one dipole pattern opposed in phase to the other dipole pattern) relatively rotated by 45, with the output of one quadrupole shifted in phase by Alternatively (or as a supplement) mixing circuits obtained by appropriate modification of those previously described may be employed.
  • An attenuation factor equal to the square root of a constant m may be applied to the transmission signals T and T in the formation and conjugate-function decoding of these auxiliary transmission signals.
  • the overall presentation signals are in this case of the form:
  • phase relations of the source-signal components in each presentation signal are the same as in the twochannel case. However the 90 separation is vastly improved, as now seen.
  • 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 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.
  • the encoding function f 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. Th 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 difierence-angleargument 0:.
  • Similar encoding functions may be employed for larger numbers of transmission signals corresponding to equally spaced directional angles.
  • the encoding function is and the decoding function of 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. It will be seen that this overall function is exactly the same as that obtained with the unmodified compatible three-channel system set forth above at (5). It may be demonstrated that the compatible and equalspaced" transmission signals are each linear combinations of the other, i.e., derivable from each other by reversible methods of linear combination which produce no change in the information content.
  • Such encoding is particularly useful in the making of discrete-signal four-track recordings, which can be played back with any desired speaker array.
  • a signalprocessing apparatus for use in the production or reproduction of multidirectional audio signals comprising matrixing means for producing a set of output signals from a set of input signals, each signal of at least one of said sets being identified with a different sound-direction bearing angle, means for mixing the input signals with mixing coefficients defined for each respective value of a 360 repetitive single-variable function of bearing angle for each output signal to provide the respective output signals, said single-variable functions having the characteristic that when each output signal is multiplied by the complex conjugate of the respective function of another bearing angle and all such products are added, the sum produced thereby is a sum of input signals each multiplied by a coefficient that is a function solely of the difference between both bearing angles.
  • a method of reproducing directional audio information from a plurality of source signals to form a plurality of presentation signals comprising the steps of: matrixing source signals representative of sounds from different bearing angles 0, each measured from a source reference direction, to form transmission signals having encoding mixing coefficients, at least one of said transmission signals having encoding mixing coefficients substantially corresponding to values of a given single-variable function of the bearing angle 0 of the respective sounds, re-matrixing the transmission signals to form signals for presentation at bearing angles 4), each measured from a presentation reference direction having a specific angular relation to said source reference direction, by multiplying each transmission signal by a decoding mixing coefficient substantially corresponding to the vlaue of a single-variable function of d) for each presentation bearing angle, said function of 5 being the complex conjugate of the function of 0 defining the encoding mixing coefficients for each transmission signal, and adding the resultant product signals to form each presentation signal, so that the sum of all products of the function of applied to source signals in formation of each transmission signal with the function
  • An audio recording having transmission signals formed from the matrixing of a plurality of source signals representative of sounds from different bearing angles 6 and capable of being re-matrixed for production of a plurality of presentation signals at bearing angles (1), the bearing angles 0 being measured from a source reference direction and the bearing angles :10 being measured from a presentation refererence direction having a specific angular relation to said source reference direction, at least one of said transmission signals including the sum of mixed signals each formed by mixing the source signals with mixing coefficients defined for each respective value of a given 360 repetitive single-variable function of the bearing angles 0 for each transmission signal, and said given single-variable function has the characteristic that when it is multiplied by the complex conjugate of said function of the bearing angle (1) and all such product functions are added, the sum produced thereby is a function solely of the difference between said bearing angles 6 and 42, and has a maximum absolute value at a reference difference angle, a relatively small absolute value at the diametrically opposite difference angle and absolute values at intermediate angles symmetrical with respect to the axi
  • a signal-processing system for producing or reproducing directional audio information comprising encoding means for matrixing source signals representative of sounds from different bearing angles 6, each measured from a source reference direction, to form transmission signals having encoding mixing coefficients, at least one of said signals having encoding mixing coefficients substantially corresponding to values of a given single-variable function of the bearing angle of the respective sounds, decoding means for rematrixing the transmission signals to form signals for presentation at bearing angles 4), each measured from a presentation reference direction having a specific angular relation to said source reference direction, said decoding means having means for multiplying each transmission signal by a decoding mixing coefficient substantially corresponding to the value of a singlevariable function of d) for each presentation bearing angle, said function of (i) being the complex conjugate of the function of 6 defining the encoding mixing coefficients for each transmission signal, and means for adding the resultant product signals to form each presentation signal, so that the sum of all products of the function of 0 applied to the source signals in formation of each transmission signal with the function of (i)
  • a signal-processing apparatus for reproducing directional audio information from a plurality of source signals to form a plurality of presentation signals, wherein the source signals are representative of sounds from different bearing angles 0, each measured from a source reference direction, to form transmission signals having encoding mixing coefficients, at least one of said signals having encoding mixing coefficients substantially corresponding to values of a given single-variable function of the bearing angle 0 of the respective sounds, said apparatus comprising decoding means for re-matrixing the transmission signals to form signals for presentation at bearing angles (b, each measured from a presentation reference direction having a specific angular relation to said source reference direction, said decoding means having means for multiplying each transmission signal by a decoding mixing coefficient substantially corresponding to the value of a singlevariable function of qb for each presentation bearing angle, said function of (I) being the complex conjugate of the function of 0 defining the encoding mixing coefficients for each transmission signal, and means for adding the resultant product signals to form each presentation signal, so that the sum of all products of the source
  • n TA 2 Sk(icos 6 sin 6 2 S j(9+1r/ where S is the k-th source signal, 0;,- is the bearing angle between the sound location thereby represented and a laterally central reference location and j is the square root of l.
  • each presentation signal contains the corresponding-location source signal plus each of the adjacent-location source signals, both of the latter being reduced to 0.707 in relative amplitude, and one of them being advanced in relative phase by 45 and the other being retarded in relative phase by 45, with respect to the corresponding location signal.
  • the signal-processing apparatus of claim 1 comprising an encoder having input sound-source signals of various bearing angles and output transmission signals.

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US00187065A 1971-10-06 1971-10-06 Multidirectional sound reproduction Expired - Lifetime US3856992A (en)

Priority Applications (19)

Application Number Priority Date Filing Date Title
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
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 (enrdf_load_html_response) 1971-10-06 1972-10-06
JP47100548A JPS582519B2 (ja) 1971-10-06 1972-10-06 ホウコウセイオ−デイオジヨウホウ ノ サイセイホウホウ
DE2249039A DE2249039C2 (de) 1971-10-06 1972-10-06 Verfahren zur Aufnahme und Wiedergabe von richtungsbezogener Schallinformation
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
CA252,646A 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
CA252,647A CA1006824A (en) 1971-10-06 1976-05-17 Signal matrixing for directional reproduction of sound
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
CA252,644A CA1006830A (en) 1971-10-06 1976-05-17 Signal matrixing for directional reproduction of sound
US05/701,228 US4085291A (en) 1971-10-06 1976-06-30 Synthetic supplementary channel matrix decoding systems
US05/836,507 US4152542A (en) 1971-10-06 1977-09-26 Multichannel matrix logic and encoding systems

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US05/468,238 Continuation-In-Part US3985978A (en) 1971-10-06 1974-05-09 Method and apparatus for control of FM beat distortion
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
US05/578,078 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 (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3982069A (en) * 1974-10-16 1976-09-21 Sansui Electric Co., Ltd. Decoding apparatus for use in matrix four channel systems of a plurality of types
US3997725A (en) * 1974-03-26 1976-12-14 National Research Development Corporation Multidirectional sound reproduction systems
USRE29171E (en) * 1971-07-02 1977-04-05 Sansui Electric Co., Ltd. Multi-directional sound system
DE2711299A1 (de) * 1976-03-15 1977-09-22 Nat Res Dev Tonwiedergabesystem
US4072821A (en) * 1976-05-10 1978-02-07 Cbs Inc. Microphone system for producing signals for quadraphonic reproduction
US4081606A (en) * 1975-11-13 1978-03-28 National Research Development Corporation Sound reproduction systems with augmentation of image definition in a selected direction
US4096353A (en) * 1976-11-02 1978-06-20 Cbs Inc. Microphone system for producing signals for quadraphonic reproduction
US4251685A (en) * 1971-02-02 1981-02-17 National Research Development Corporation Reproduction of sound
US4910778A (en) * 1987-10-16 1990-03-20 Barton Geoffrey J Signal enhancement processor for stereo system
US6072878A (en) * 1997-09-24 2000-06-06 Sonic Solutions Multi-channel surround sound mastering and reproduction techniques that preserve spatial harmonics
US20070177752A1 (en) * 2006-02-02 2007-08-02 General Motors Corporation Microphone apparatus with increased directivity
US20100131417A1 (en) * 2008-11-25 2010-05-27 Hank Risan Enhancing copyright revenue generation
US20100145486A1 (en) * 2008-12-10 2010-06-10 Sheets Laurence L Method and System for Performing Audio Signal Processing
US20110035686A1 (en) * 2009-08-06 2011-02-10 Hank Risan Simulation of a media recording with entirely independent artistic authorship
US11120819B2 (en) * 2017-09-07 2021-09-14 Yahoo Japan Corporation Voice extraction device, voice extraction method, and non-transitory computer readable storage medium

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5228361B2 (enrdf_load_html_response) * 1972-03-09 1977-07-26
JPS582520B2 (ja) * 1972-09-13 1983-01-17 ナシヨナル・リサ−チ・デイベロプメント・コ−ポレ−シヨン ホウコウセイオ−デイオジヨウホウノ サイセイホウホウ
JPS5343401B2 (enrdf_load_html_response) * 1973-12-17 1978-11-20

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3632886A (en) * 1969-12-29 1972-01-04 Peter Scheiber Quadrasonic sound system

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3632886A (en) * 1969-12-29 1972-01-04 Peter Scheiber Quadrasonic sound system

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
4 Channels and Compatibility by Scheiber, Audio Engineering Society Preprint, Oct. 1970. *
Analysing Phase Amplitude Matrices by Scheiber, Audio Engineering Society Preprint, Oct. 5 8, 1971. *

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4251685A (en) * 1971-02-02 1981-02-17 National Research Development Corporation Reproduction of sound
USRE29171E (en) * 1971-07-02 1977-04-05 Sansui Electric Co., Ltd. Multi-directional sound system
US3997725A (en) * 1974-03-26 1976-12-14 National Research Development Corporation Multidirectional sound reproduction systems
US3982069A (en) * 1974-10-16 1976-09-21 Sansui Electric Co., Ltd. Decoding apparatus for use in matrix four channel systems of a plurality of types
US4081606A (en) * 1975-11-13 1978-03-28 National Research Development Corporation Sound reproduction systems with augmentation of image definition in a selected direction
DE2711299A1 (de) * 1976-03-15 1977-09-22 Nat Res Dev Tonwiedergabesystem
US4072821A (en) * 1976-05-10 1978-02-07 Cbs Inc. Microphone system for producing signals for quadraphonic reproduction
US4096353A (en) * 1976-11-02 1978-06-20 Cbs Inc. Microphone system for producing signals for quadraphonic reproduction
US4910778A (en) * 1987-10-16 1990-03-20 Barton Geoffrey J Signal enhancement processor for stereo system
US6904152B1 (en) 1997-09-24 2005-06-07 Sonic Solutions Multi-channel surround sound mastering and reproduction techniques that preserve spatial harmonics in three dimensions
US6072878A (en) * 1997-09-24 2000-06-06 Sonic Solutions Multi-channel surround sound mastering and reproduction techniques that preserve spatial harmonics
US20050141728A1 (en) * 1997-09-24 2005-06-30 Sonic Solutions, A California Corporation Multi-channel surround sound mastering and reproduction techniques that preserve spatial harmonics in three dimensions
US7606373B2 (en) 1997-09-24 2009-10-20 Moorer James A Multi-channel surround sound mastering and reproduction techniques that preserve spatial harmonics in three dimensions
US20070177752A1 (en) * 2006-02-02 2007-08-02 General Motors Corporation Microphone apparatus with increased directivity
US7813519B2 (en) 2006-02-02 2010-10-12 General Motors Llc Microphone apparatus with increased directivity
US20110026753A1 (en) * 2006-02-02 2011-02-03 General Motors Llc Microphone apparatus with increased directivity
US8325959B2 (en) 2006-02-02 2012-12-04 General Motors Llc Microphone apparatus with increased directivity
US20100131417A1 (en) * 2008-11-25 2010-05-27 Hank Risan Enhancing copyright revenue generation
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
US20110035686A1 (en) * 2009-08-06 2011-02-10 Hank Risan Simulation of a media recording with entirely independent artistic authorship
US11120819B2 (en) * 2017-09-07 2021-09-14 Yahoo Japan Corporation Voice extraction device, voice extraction method, and non-transitory computer readable storage medium

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