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US2093540A - Sound-transmission, sound-recording, and sound-reproducing system - Google Patents

Sound-transmission, sound-recording, and sound-reproducing system Download PDF

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Publication number
US2093540A
US2093540A US647057A US64705732A US2093540A US 2093540 A US2093540 A US 2093540A US 647057 A US647057 A US 647057A US 64705732 A US64705732 A US 64705732A US 2093540 A US2093540 A US 2093540A
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Prior art keywords
sound
impulses
microphones
channels
recording
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US647057A
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English (en)
Inventor
Blumlein Alan Dower
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EMI Ltd
Electrical and Musical Industries Ltd
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EMI Ltd
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Priority claimed from GB3465731A external-priority patent/GB394325A/en
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Priority claimed from GB450134A external-priority patent/GB429054A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R5/00—Stereophonic arrangements
    • H04R5/04—Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R11/00—Transducers of moving-armature or moving-core type
    • H04R11/08—Gramophone pick-ups using a stylus; Recorders using a stylus
    • H04R11/12—Gramophone pick-ups using a stylus; Recorders using a stylus signals being recorded or played back by vibration of a stylus in two orthogonal directions simultaneously
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/12—Gramophone pick-ups using a stylus; Recorders using a stylus
    • H04R9/16—Gramophone pick-ups using a stylus; Recorders using a stylus signals recorded or played back by vibration of a stylus in two orthogonal directions simultaneously
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S1/00—Two-channel systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S1/00—Two-channel systems
    • H04S1/002—Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution

Definitions

  • This invention relates to the transmission, recording andreproduction of sound and is more particularly directed to systems for recording and reproducing speech, music and other sound 5 effects. It is applicable in particular, although not exclusively, to systems associated with picture effects as in talking motion pictures.
  • the fundamental object of the invention is to provide a sound recording, reproducing and/or transmission system whereby there is1,conveyed to the listener a realistic impression that the intelligence is being communicated to him over two illusion that the sound is coming, and is only coming, from, the artist or other sound source presented to the eye.
  • the invention is not, however, limited to use in connection with picture effects, but may, for example, be used for imp-roving the qualities of public address, telephone or radio transmission systems, or for improving the quality of sound recordings.
  • recording music considerable trouble is experienced with the unpleasant effects produced by echoes which in the normal way would not be noticed by anyone listening in the room in which the performance, is taking place.
  • An observer in the room is listening with two ears, so that, echoes reach him with the directional significance which he associates with the music performed in such .a room. He therefore discounts these echoes and psychologically focuses sound sources, sound waves emitted thereby, and
  • this directional effect can also be obtained, for example, in a studio. If, however, the channels are not kept separate (as, for example, is the case in previously proposed arrangements for recording and/or reproducing sound, in which sounds picked up by a plurality of microphonesare led to loud speakers which take the place of the headphones) the effect is almost entirely lost and such systems have therefore not come into common use since they are quite unsatisfactory for the purpose.
  • the present invention contemplates controlling the soundyemitted for example by such loud speakers, in such a way that the directional effect will be retained.
  • phase differences are phase differences and intensity differences between the sounds reaching the depending upon the frequency of the sounds emitted.
  • intensity differences For low frequency sound waves, there is little or no difference in intensity at thetwo ears but there is a marked phase difference.
  • the phase difference is approximately proportional to frequency, representing a fixed time delay between sound arriving at the two cars, by noting which the brain decides the direction from which the sound arrives.
  • phase differences necessary at the ears for low-frequency directional sensation are not produced solely by phase differences at two loud speakers (both of which communicate with both ears) but that intensity differences at the speakers are necessary, while initial intensity differences from the sources necessary for hi.i.1-fre-- quencies are not sufficiently marked when the sounds reach the ears, and to produce suitable effects, therefore, the initial intensity differences must be amplified. It is for this reason that the aforementioned methods previously proposed are not successful in achieving the desired effect,
  • the invention consists broadly in so controlling the intensities of sound to be, or being, emitted by a plurality of loud speakers or similar sound sources, in suitable spaced relationship to the listener, that the listeners ears will note low-frequency phase differences and high-frequency intensity differences suitable for conveying to the brain a desired sense of direction of the sound origin.
  • the direction from which the sound arrives at the microphones determines the characteristics (more especially, as will become apparent hereinafter, the intensities) of the sounds emitted by the loud speakers in such a way as to provide this directional sensation.
  • control may be wholly effected either during the recording or during reproduction, or may be partially carried out in each stage.
  • the invention consists in a system of sound transmission, recording and/or reproduction wherein the sound is picked up by a plurality of microphone elements and reproduced by a plurality of loud speakers, comprising two or more directionally sensitive microphones and/or an arrangement of elements in the transmission circuit or circuits whereby the relative loudness of the loud speakers is made dependent upon the direction from which the sounds arrive at the microphones.
  • the invention also consists in a system of sound transmission, recording and/or reproduction wherein the sound is received by two or more microphones and wherein, at low frequencies, difference in the phase of sound pressure at the microphones is reproduced as difference in volume at the loud speakers.
  • the invention further consists in a system of sound transmission, recording and/or reproducticn, in which the original sound is detected by two or more microphones of a type such as velocity microphones whose sensitivity varies with the direction of incident sound, and in which the dependence of the relative responses of the microphones to the direction of an incident sound Wave is used to control the relative volumes of sound emitted by two or more loud speakers.
  • a type such as velocity microphones whose sensitivity varies with the direction of incident sound
  • the dependence of the relative responses of the microphones to the direction of an incident sound Wave is used to control the relative volumes of sound emitted by two or more loud speakers.
  • the invention also consists in a system of sound transmission, recording and/or reproduction wherein impulses from two microphones transmitted over individual channels are adapted to interact whereby the two impulses further transmitted consist in half the sum and half the difference, respectively, of the original impulses, said impulses being thereafter modified to control the relati'e loudness of loud speakers whereby the sound is to be reproduced.
  • the invention also consists in a system of sound transmission, recording and/or reproduction wherein the sound is picked up by two directionally sensitive microphones which are so spaced and/ or with their axes of maximum sensitivity so directed relative to one another and to the sound source, that the relative loudness of loud speakers which reproduce the impulses is controlled by the direction from which the sound reaches the microphones.
  • the invention also consists in a system as set forth above wherein the impulses are recorded in the transmission between the microphones and the loud speakers.
  • the invention also consists in a system, as set forth above, wherein two impulses are mechanically recorded in the same groove.
  • the invention also consists in a system, as set forth above, wherein the impulses are transmitted by radio telephony.
  • the invention also consists in a system, as set forth above, in combination with means for the photographic recording or transmission and/or reproduction of pictures.
  • the word channel means an electric circuit carrying a curren, having a definite form depending upon the original sounds in the studio.
  • two channels may be different not because the average intensities or types of current in them differ but because they originate from two microphones in different positions in the studio.
  • Figure 2 represents a microphonic arrangement for use according to one form of the invention
  • Figure 3 represents atransformer arrangement employed in one form of the invention
  • Figure 4 shows a symbolic representation of th arrangement shownin Figure 3
  • Figures 5, 6 and 7 represent variouscircuit arrangements applicable to various forms of the invention, while Figures 8, 9, 10 and 11 represent different forms of sound recorders which may be employed.
  • the sounds to be recorded and reproduced with the pictures may be received from a source a by two pressure microphones a1.
  • a2 mounted on opposite sidesof a block of wood or baffle b which serves to provide the high fre quency intensity differences at the microphones in the same way as the human head operates upon the ears as indicated above.
  • the outputs from the two microphones are, after separate amplification by separate similar amplifiers bi,
  • circuits 0 comprising transformers or bridge or network circuits which convert the two primary channels into two secondary channels which may be called the surnmation and difference channels. These are arranged so that the current flowing into the summation channel will represent half the sum, or the mean, of the currents flowing in the two original channels, while the current flowing into the difference channel will represent half the difference of the currents in the original channels.
  • FIG. 3 One convenient transformer arrangement for this purpose is shown in Figure 3 wherein input currents from amplifiers b1, b2 are separately fed each to two primary windings, one on each of two transformers, the secondary winding of ⁇ each transformer providing a sum or difference output current on account of the senses in which the pimary coils are woundas shown.
  • a diagrammatic representation of a sum and difference arrangement (which may consist of a transformer similar to that of Figure 3 or any other suitable arrangement of circuit elements) is shown in Figure 4. i
  • Figure 5 which represents the portion of the'circuits indicated bye in Figure l 1.
  • the current in the difference channel will be role 75 the voltage across the condenser f in the difference channel.
  • These two voltages are then combinedand reseparated by a sum and difference process such as previously adopted so as to produce two final channels.
  • the voltage in the first final channel will be the sum of these voltages and the-voltage in the second final channel will be the difference between these voltages.
  • the two final channels will be in phase but will differ in magnitude.
  • the value of the shunt resistance 2' in the summation channel and the shunt condenser fin the difference channel for a given frequency any degree of amplitude difference in the final channels can be obtained for a given phase difference-in the original channels.
  • the phase difference between the waves will, for a given obliquity "in-the difference circuit will have the effect of producing a fixed intensity difference in the final channels for a given obliquity at all low frequencies.
  • the shunt condenser f in the difference circuit is therefore built out with a resistance k whose value determines the degree of modification.
  • the capacity of the condenser is of such value that its impedance issmall compared with that of the series resistances d and 6 over the whole working range, wlnle the value of resistance is such that it equals the reactance of the condenser at approximately the frequency above which it is desired not to convert phase differences into amplitude differences. that of i, in. which casethe amplitude differences for high frequencies are augmented in the final outputs.
  • the outputs from the modifying circuit 0 are passed to amplifiers d1, (Z2 and thence to loud speakers e1, e2 suitably disposed on each side of a picture screen. It is to be understood that Figure 1 merelytraces the passage of intelligence from the source a to a recipient and no recording or reproducing system has been shown. Such may, however, be inserted anywhere along the electrical circuit such for example as between amplifiers b1, b2 and modifying assembly 0, or between assembly c and amplifiers d1, d2.
  • the impulses transmitted through the two channels as indicated above may, for example, be recorded on two sound tracks on a film by any suitable or known means, each of which records may comprise either a sound track of constant density and variable width (e. g. an oscillograph record), or a sound track of constant width and variable density (e. g. a light valve record).
  • records may comprise either a sound track of constant density and variable width (e. g. an oscillograph record), or a sound track of constant width and variable density (e. g. a light valve record).
  • the modifying circuit may be arranged to convert phase differences into amplitude differences throughout the entire frequency range.
  • the phase differences dealt with at the low-frequencies may be so small that, in this case, slight differences in the two microphone circuits would have very large effects.
  • microphone spacing of the same order as that of the human ears is most suitable.
  • 0 angle of obliquity, in radians, of the source from the median plane between the microphones.
  • s width of screen of theatre.
  • the portion is a factor of the recording, and is constant for a given arrangement if either the camera is in line with the microphones and the centre of the picture, or the action does not move appreciably to or from the microphones and camera.
  • the relative distances of camera and microphones and the focal length of the lens may be adjusted to maintain this factor a constant.
  • the expression is a constant for the theatre. As regards low frequencies only, the distance apart of the speakers need not exceed the screen width, but should certainly not be closer than per cent. of the screen width. The closer the loud speakers, the greater the necessary power handling capacity, but the less the troubles introduced by formation of stationary waves.
  • the modifying networks and channel arrangements may be employed between the microphones and the film during recording, or between the record and the loud speakers during reproduction, and the latter course, in addition to allowing of adjustment of the arrangements to suit the particular theatre as indicated above, has the additional advantage that the sound film can be reproduced by a single reproducing head or channel if, for example, one of the dual arrangements breaks down, or in a theatre which, having one installation, does not wish to go to the expense of installinga second apparatus.
  • volume indicator measurements may be made with a standard sound source placed at the extremes of the set, i. e., the space within which recording is to be effected, and from these the proposed modifying network laid out.
  • a further experiment may also be effected to standardize phase angles on the film.
  • a simple adjustment may be provided to check and balance the input to the two channels, a length of test film being used for this purpose.
  • the total theatre equipment necessary is very simple and consists in a transmission modifier (comprising two or four transformers, for example, artificial line resistances and the control network, which may be no more than a condenser and a resistance) and two normal soundreproducing heads or pick-ups, or one especially designed head or pick-up adapted to separate the two recordings to two complete reproducing channels.
  • a transmission modifier comprising two or four transformers, for example, artificial line resistances and the control network, which may be no more than a condenser and a resistance
  • two normal soundreproducing heads or pick-ups or one especially designed head or pick-up adapted to separate the two recordings to two complete reproducing channels.
  • the binaural transfer frequency (from phaseto intensity-discrimination) need have no definite significance in recording, since it is a function of the human. brain, it is, nevertheless, necessary to fix a change-over frequency from highto low-frequency working for recording, since this frequency fixes the values of the elements in the modifier and thus the form of modification to be used, the distance apart of the microphones and the form of bafiie between them. Any convenient frequency may be chosen as standard after experience has decided which is most suitable. Instead of stand ardizing, it may be possible from the preliminary experiments to allow electrically for variation of microphone positions and/or of microphone spacing (although the latter would be extremely difi'icult) and it must be understood that this arrangement falls within the scope of the invention.
  • Directionally sensitive miorophones may also be employed spaced a small distance apart, the outputs being modified as indicated so that the relative outputs ofthe loud speakers are controlled both by differences in phase and differences in magnitude of the microphone outputs.
  • Such directionally sensitive microphones may be,
  • velocity microphones but are not necessarily, of the type known as velocity microphones.
  • Velocity or moving conductor microphones are very suitable for any system according to the invention and, in addition to use with circuit arrangements described above, they may also be employed with various alterations in the circuits. These microphones give a response varying as the cosine of the, angle of incidence of the sound relative to the direction of normal or optimum incidence, and they therefore have the advantage that a specific degree of loud speaker output separation may be obtained without phase-conversion or like network modifications.
  • Two velocity microphones are placed one with its axis directly facing in the direction of the centre of the scene, and the other with its axis at right angles to that direction.
  • Such sum and difference arrangement differs from the modifying network employed with pressure microphones in that the pressure type provide phase differences (whereby direction is determined) which have to be converted, whereas with the velocity type the edgeon microphone provides an output proportional to the obliquity of the source.
  • a suitable modifying arrangement for this form of the invention is shown in Figure 6.
  • Two velocity microphones, or microphone elements may be placed with their axes perpendicular to one another and each axis at 45 to the direction of the centre of the screen.
  • This arrangement is represented diagrammatically in Figure 2 wherein n and 0 represent two velocity, or directionally sensitive, microphones one above the other arranged perpendicular to one another and at equal angles of 45 to the direction of the centre of the field from which sound is to be received. It will be clear that movement of the sound source w laterally to a position p removed from the centre of the field will result in the sound waves striking 0 at a more acute angle than they strike n and differences in the microphone outputs will result.
  • the microphones are sufficiently close together to render phase differences of the incident sound negligible and the output amplitudes therefore differ approximately proportionally .to the obliquity of the incident sound. They may, therefore, be amplified simi larly and supplied directly to the loud speakers to which they Will give the correct amplitude differences for the desired directional effect, provided the relationship between the various dimensions of the recording and reproducing lay-outs are correct. If it is desired to accommodate any differences between the lay-outs, the outputs may be modified by networks, in the manner described, suitably to increase or decrease the differences between them. An arrangement such as shown in Figure 6 is suitable for this purpose, and such an arrangement may, of course, also be employed even if the lay-out is correct if it is desired for any reason to control or modify the amplitude differences of the loud speaker outputs.
  • (3)Two microphones may be arranged with the two axes lying symmetrically to the direction of the centre of the field and with an angle between them of say 0 degrees, so that sound from a performer at the centre subtends an angle of degrees to each microphone. If 0 is small, a small movement of the performer to one side is sufficient to make one microphone edge-on and to reduce its output to zero, while if 0 is large a large movement of the performer is necessary to do this.
  • 0 adjustable different layouts may be accommodated without the modifi cation indicated under (2), and it will be clear, also, that this provides a method of directional sound transmitting, recording and reproduction which avoids the necessity of combining and reseparating the two channels.
  • the microphone elements in any of the above cases may be enclosed in a single casing if .de-
  • Two velocity microphones set with their axes symmetrically inclined to the direction of the centre line of the scene may, if placed one above the other, be employed also to provide significance of vertical as well as horizontal movement of the sound source.
  • Such vertical displacement of the source will, in this arrangement, give phase differences to the outputs, while lateral displacements give amplitude differences, and these can be separated, the phase differences converted to intensity differences by modifying networks, as described, and the resulting impulses employed to operate four or more loud speakers distributed around the screen, the transmission occupying, however, only two channels.
  • a similar effect may be obtained with a plurality of pressure microphones by employing suitable modification previous to transmission.
  • the invention is not limited solely to the use of two microphones.
  • a plurality may be employed and their outputs suitably collected and/or modified and/or separated to transmit suitable differences of impulses to a plurality of loud speakers.
  • the general feature is that two transmitting channels receiving impulses from two or more microphones, for example, communicate two directional senses at right angles to one another, the sounds whereby this is done being provided by a plurality of loud speakers.
  • the outgoing channels 1) and w whose difference is to be a modification of the original difference, are connected by one wire each to the common point t of the original channels, and by their other wires to tappings along the choke u, If the differences are to be increased, the tappings at which the output channels are connected lie outside the tappings to which the input channels are connected, so that the choke operates in effect as an autotransformer amplifying the difference voltages. Similarly, for a reduction of differences, the output channels are tapped intermediately between th two input channels. Modifications of this arrangement in which the devices are balanced about earth, etc. may be arranged, but the chief advantage is that the modification is varied entirely by altering tappings along a transformer or choke, and that no great power loss is involved.
  • This arrangement of a choke or transformer is well suited to working a number of loud speakers for binaural reproduction.
  • the two outputs from power valves are fitted to a choke such as 11. along which the loud speakers are tapped.
  • the position of the loud speaker tappings can be adjusted to suit their relative positions, and it can be arranged that the valves are working into their best impedances.
  • Transformers may be used to ensure the speakers taking their correct fraction of the output.
  • the invention is not limited to that medium since the recording may, if desired, be effected on discs or cylinders of suitable material.
  • the two channels may, if desired, be recorded in separate grooves but it is preferred that they be recorded in the same groove having a hill-and-dale and also a lateral cut movement.
  • a wax disc has a sound record as a hill-and-dale cut and a picture record as a laterally cut V-shaped groove at the bottom of the hill-and-dale groove, or vice versa.
  • the two channels being recorded are directly picked up from two microphones, or are intended to work unmodified into two speakers, that is, with intensities .and qualities similar, it is preferred not to cut one track as lateral cut and the other as hill-and-dale, but to cut them as two tracks whose movement axes lie at 45 to the wax surface, or at some other convenient angle dependent on the relative available intensities from lateral cut and hill-and-dale respectively. If, however, the two channels recorded are such as summation .and difference channels, it is preferred to separate them completely into pure hill-anddale and pure lateral out, i. e., to make the recording axes normal and tangential to the wax surface.
  • a record cut as a combined hill-and-dale and lateral cut record may be reproduced, if desired, as two skew direction cuts, the basic principle being that the groove has amplitude in any direction in the plane at right angles to the direction of wax movement, and the recording and reproducing directions may be chosen as any pair of axes lines, not necessarily at right angles, in this plane.
  • the track section is preferably adapted to work with a sapphire and have a sufficiently fine angle to give lateral as well as vertical control tothe to thewax surface.
  • Figure 8 shows schematically a recorder of this kind suitable for producing records having complex cuts.
  • l and 2 represent the driving elements of two; recorders normally adapted for cutting lateralcut records; These driving elements drive arms 3 and 4 about axes at right anglesto theplaneof thepaper within I and 2.
  • FIG. 9 Another such form of recorder shown in Figure 9, represented a moving iron recorder, may
  • reed 9 mounted closely above T and parallel with the wax track and carrying the cutting sapphire 8.
  • This reed 9 may extend backwards perpendicularly to the paper to supports (not shown) which jointhe top of a laminated pole system l0 tofComplete a polarizingmagnetic system therewith.
  • the two laminated arms of the pole piece It! extend down towards the free endof thereed 9. These arms form two-poles in a direction at to the wax surface.
  • each pole being adapted to pull the reed reed maybesuitably damped, e. g., by a rubber line, and have a resonant frequency at the top'of,
  • the two pole pieces may be wound with speech coils and the energization of one of these moves the sapphire in an upward direction at 45 to the wax surface.
  • the terminals of one channel are connected to main winding I2 and compensating windingll.
  • terminals [6 of the other channel are connected to main winding M and compensating winding [3.
  • anyother movement axes may be obtained.
  • An alternative movingicoil design which may employ electromagnetic damping may consistof a it is moving member in theshape of a T as; shown in Figure 10.
  • the recorder sapphire 8 is supported on a light T member ll, whichis supported at l8
  • the by elastic means such that it mayrotate about this point, and may also translate vertically, although it is resistant to movements in the plane of the paper.
  • the device is driven by moving coils l9 and 20 which are located in annular gaps in a magnetic system, not shown. Current in one of the moving coils tends to both rotate and translate the device so that the sapphire 8 moves along an axis at approximately 45 to the vertical.
  • the movement of this device may be damped and equalized along the lines described in British patent specification No. 350,998.
  • any required axes of movement may be obtained by suitable interconnection of the two driving coils.
  • Such a movement preferably has the same natural frequency for both rotation and translation.
  • the distributionof mass is preferably such that a small instantaneous force applied at one coil produces no movement at the other.
  • Figure 11 shows another form of recorder similar in principle to the one shownin Figure 10 except that a moving iron drive is employed.
  • the member I! moving about axis 58 is constructed of magnetic material, or has a magnetic upper portion.
  • is polarized either by being partially permanently magnetized, or having a magnetizing winding on it, so that the central pole is of opposite polarity to the two outer poles. Speech windings on the outer poles are brought out to terminals l5 and it to which the two channels are connected.
  • angles of the axes defining themovements ofthe sapphire can be altered by suitably connecting the speech windings; for instance, axes which are normally inclined at 45 to the wax surface can be converted into pure hill and dale and lateral cut axes by arranging thatthe speech windings are in series aiding for one channel and opposing for the other channel.
  • any of the speech windings for instance, axes which are normally inclined at 45 to the wax surface can be converted into pure hill and dale and lateral cut axes by arranging thatthe speech windings are in series aiding for one channel and opposing for the other channel.
  • axis conversion can be effected by suitably com-- bining the channels through transformers.
  • radio transmission may, if desired, be employed.
  • Each channel may be separately transmitted or preferably the methods described in the specification of copending Cognate British patent applications Nos. 30,712 of 1931 and 24,423 of 1932, whereby two signals from a common source are transmitted over a single carrier wave, may be employed.
  • the methods described in those two specifications comprise the separate modulation by signals from a common source of two carrier waves 90 different in phase, which are thereafter combined to form a single wave which is transmitted.
  • the 90 phase difference enables the wave to be broken into its. appropriate components by suitable means at the receiver and the signals to be separately reproduced.
  • Another method also de'- scribed comprises the modulation of a single carrier wave by two signals from a common source, one modulating the carrier in frequency and the other modulating it in amplitude.
  • Suitable receiving apparatus enables these signals to be separately received and reproduced independently. It should be added that duplex radio-signalling is well known and the novelty thereof in the present application resides only in its use in the binaural systems described above in accordance with the present invention.
  • the secondary impulses obtained as sum and difference effects from the initial impulses may conveniently be obtained by shifting the phase of the transmitted carrier wave through 45.
  • the general transmission arrangement may be substantially as described in the specification referred to and any convenient or known means may be utilized for effecting If, for example, B and B in Figure 2 of that specification form parts of balanced modulator systems, the outputs from which are free from any carrier waves, a separate carrier wave amplifier may be added enabling a carrier wave to be injected into the aerial in any desired phase.
  • transmission may be effected by modulation of phase and amplitude of the carrier wave by the signals originating from the two microphones, and reception effected by apparatus such as shown in Figure 3 of the specification referred to, in which case signals are received proportional to the sum and difference respectively of the signals modulating the carrier wave.
  • the hereindescribed system while being especially applicable to talking pictures, is not limited to such use. It may be employed in recording sound quite independently of any picture effects and in this connection (as well as when used in cinematograph work)v it seems probable that the binaural effect introduced will be found to improve the acoustic properties of recording studios and to save any drastic acoustic treatment thereof while providing much more realistic and satisfactory records for reproduction. Furthermore, the system may clearly be employed when the microphone outputs are led directly to the loud speakers instead first of being recorded, and such an arrangement may, for example, be employed in public address systems in which directional sound effects are desired; In general, the invention is applicable in all cases where it is desired to give directional effects to emitted sound.
  • the total modification and/or interaction of the channels may be accomplished in more than one stage.
  • the low frequency phase differences may be amplified, the medium frequency phase differences converted to amplitude differences, and the high frequency amplitude differences augmented in a first stage of modification; the low frequency phase differences may then be converted to amplitude differences in a later stage of modification.
  • One or both of these stages may occur either before or after the sound has been recorded. In this manner, the very small low frequency phase differences are augmented before they are amplified, so avoiding troubles due to small low frequency phase shifts in amplifiers.
  • a system of sound transmission comprising a plurality of microphone elements, a plurality of loud speakers adapted to receive and reproduce impulses from said microphone elements, and electrical elements in the circuit between said loud speakers and said microphone elements adapted to control the relative loudness of said loud speakers in accordance with the direction of incidence of the sounds on said microphone elements.
  • a system of sound transmission comprising a plurality of microphone elements, a plurality of loud speakers for receiving and reproducing impulses from said microphone elements, and means for controlling the relative loudness of said loud speakers in accordance with the direction from which the sounds arrive at said microphones, said means including electrical connections in the transmission circuit adapted to combine the impulses from the said microphones and reseparate them into a plurality of impulses of different form.
  • a system of sound transmission comprising a plurality of microphone elements, a plurality of loud speakers for receiving and reproducing impulses from said microphone elements, and means for controlling the relative loudness of said loud speakers in accordance with the direction from which the sounds arrive at said microphones, said means including electrical connections in the transmission circuit adapted to combine the impulses from the said microphones and reseparate them into a plurality of impulses 2,093,540 of different form; and electrical elements adapted-.
  • a system of sound transmission comprising a plurality of microphone elements, a plurality of loud speakers for receiving and reproducing impulses fromsaid microphone elements, and means for controlling the relative loudness of said loud speakers in accordance with the direction from which the sounds arrive at said microphones, said means including electrical connections in the transmission circuitadapted to combine the impulses from the said microphones and reseparate them into aplurality of impulses of different form, electrical elements adapted to modify the characteristics of said different impulses, and further electric connections adapted to recombine and again reseparate said modified impulses.
  • a system of sound transmission according, to claim 2 comprising electric connections adapted to combine two original impulses and reseparate them into two different impulses consisting respectively in half the sum and half the difference of the original impulses.
  • a system of sound transmission according to claim 3 comprising an attenuator network adapted to modify the characteristics of said impulses.
  • a system of sound transmission according to claim 3 comprising a phase modifying arrangement of elements adapted to alter the characteristics of said impulses.
  • a system of sound transmission according to claim 3 comprising plain shunt elements in the transmission channels of said different impulsesadapted to modify the characteristics of such impulses.
  • a system of soundtransmission according to claim 2 comprising means adapted to convert, over part of the frequency range, phase differences between the original impulses from said microphones intoamplitude differences between the impulses of different form in the resultant channels.
  • a system of sound transmission according toclaim 2 comprising means in the resultant channels for modifying the amount of difference between the impulses therein.
  • a system of sound transmission comprising as microphone elements a plurality of strip conductors so light as to move substantially as the surrounding air, positioned longitudinally in line ing in directions equally inclined to the direction of the centre of the field in which the sound source is located.
  • a system of sound transmission according to claim 1 comprising electrical modifyingelements in the transmission channels of values defined by the formula.
  • a system of sound transmission comprising a plurality of microphone elements, a plurality of electrical channels adapted to receive impulses from said microphone elements, and electrical elements in circuit between said microphone elements and said electrical channels adapted to control the impulses generated by an elementary sound Wave arriving at said microphone elements, whereby the transmitted impulses are maintained in phase, but are rendered dependent in relative amplitude upon the direction from which the sound arrives at said microphone elements.
  • a system of sound transmission comprising a plurality of directionally sensitive microphone elements, and a plurality of electrical channels adapted toreceive impulses from said microphone elements, arranged so that the impulses in a plumeanings defined rality of said channels are combined and reseparated in such a manner that the impulses of the resultant channels, although not similar to those of the original channels, are modifications of them conveying the same directional intelligence in another form.
  • a system of sound transmission comprising a plurality of microphone elements, means for recording impulses generated in said microphone elements by the incident sounds, means for picking up said recorded impulses from said record, aplurality of loud speakers for reproducing said impulses and means adapted to control the relative loudness of said loud speakers in accordance with the direction from which sounds arrive at said microphone elements, wherein said impulses from said microphone elements are recorded unmodified, and said means for controlling the loudness of said loud speakers are incorporated in circuit between said pick-up means and said loud speakers.
  • a system of sound transmission comprising a plurality of microphone elements, means for recording impulses generated in said microphone elements by the incident sounds, means for picking up said recorded impulses from said record, a plurality of loud speakers for reproducing said impulses, means between said microphone elements and said recording means adapted partially to modify impulses from said microphone elements, and means between said pick-up and said loud speakers adapted to eifect a. further stage of modification of said impulses, whereby the relative loudness of said loud speakers is controlled in accordance with the direction from which sounds arrive at said microphone elements.
  • a plurality of microphone elements recording means for simultaneously recording different sets of imfrom which sounds arrive at said microphone elements.
  • a plurality of microphone elements adapted to move in accordance with the velocity component of the air set into vibration by the sounds being transmitted
  • recording means for simultaneously recording difierent sets of impulses comprising a cutting tool capable of controlled movement in any direction in a plane perpendicular to the direction of movement of the medium it is cutting, means for picking up said recorded impulses from said record, a plurality of loud speakers for reproducing said impulses and electrical elements in the circuit between said loud speakers and said microphone elements adapted to control the relative loudness of said loud speakers in accordance with the direction from which sounds arrive at said microphone elements.
  • a plurality of microphone elements comprising a cutting tool capable of movement in two directions, a co-operating magnetic system whereby movements of said cutting tool are controlled, energizing windings on the poles of said magnetic system for receiving impulses to be recorded, and compensating windings on said poles adapted to neutralize the magnetic effects in one pole of impulses received in the energizing windings of the other pole, means for picking up said recorded impulses from said record, a plurality of loud speakers for reproducing said impulses and means adapted to control the relative loudness of said loud speakers in accordance with the direction from which sounds arrive at said microphone elements.
  • a system of sound transmission comprising two microphone elements adapted to move in accordance with the velocity component of the air set into vibration by the sounds being transmitted, arranged with their axes of maximum sensitivity inclined to one another, two loud speakers adapted to receive and reproduce impulses from said microphone elements, four leads, one from each microphone and each loud speaker, being connected together, and the other four leads, one
  • each microphone and each loud speaker being connected to tappings on a common choke adapted to modify the impulses from said microphones prior to reproduction by said loud speakers.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Electromagnetism (AREA)
  • Stereophonic System (AREA)
  • Circuit For Audible Band Transducer (AREA)
US647057A 1931-12-14 1932-12-13 Sound-transmission, sound-recording, and sound-reproducing system Expired - Lifetime US2093540A (en)

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GB3465731A GB394325A (en) 1931-12-14 1931-12-14 Improvements in and relating to sound-transmission, sound-recording and sound-reproducing systems
GB450134A GB429054A (en) 1934-02-10 1934-02-10 Improvements in and relating to sound-transmission, sound-recording and sound-reproducing systems

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Cited By (43)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2481911A (en) * 1942-05-20 1949-09-13 Hartford Nat Bank & Trust Co Device for adjusting the stereophonic effect in devices for stereophonic transmission
US2505585A (en) * 1944-12-23 1950-04-25 Us Sec War Electroacoustic binaural listening system
US2616970A (en) * 1948-02-11 1952-11-04 Hartford Nat Bank & Trust Co Device for the transmission by electrical means of oscillations of acoustic frequency
US2710662A (en) * 1948-12-23 1955-06-14 Armour Res Found Sound projection system
US2836662A (en) * 1954-08-18 1958-05-27 Emi Ltd Electrical sound transmission systems
US2958738A (en) * 1958-01-06 1960-11-01 Erie Resistor Corp Compensating network for binaural pickup
US3013125A (en) * 1958-05-16 1961-12-12 Columbia Broadcasting Syst Inc Stereophonic recording
US3026378A (en) * 1958-04-30 1962-03-20 Rca Corp Stereophonic audio-frequency signal amplifier systems
US3047666A (en) * 1958-10-27 1962-07-31 Murray G Crosby Compatible stereophonic system
US3051798A (en) * 1958-03-05 1962-08-28 Fonofilm Ind As Device for the recording or reproduction of sound tracks
US3053943A (en) * 1957-07-12 1962-09-11 Columbia Broadcasting Syst Inc Phonograph record cutter
US3055989A (en) * 1957-08-12 1962-09-25 Columbia Broadcasting Syst Inc Ceramic reproducer
US3067295A (en) * 1958-08-04 1962-12-04 Pickering & Co Inc Stereophonic phonograph pick-up device
US3067292A (en) * 1958-02-03 1962-12-04 Jerry B Minter Stereophonic sound transmission and reproduction
US3070658A (en) * 1956-08-31 1962-12-25 Philips Corp Stereophonic sound collecting device
US3083264A (en) * 1959-12-10 1963-03-26 Bell Telephone Labor Inc Sum and difference stereophonic transmission with negative feedback
US3086780A (en) * 1960-07-26 1963-04-23 Foster Mallard Ltd Sound reproducing machines
US3115554A (en) * 1959-01-02 1963-12-24 Philips Corp Stereo transducer
US3117186A (en) * 1960-02-17 1964-01-07 Richard W Burden Compatible stereophonic broadcast system
US3118978A (en) * 1958-02-27 1964-01-21 Gen Electric Magnetic stereophonic phonograph cartridge
US3155779A (en) * 1958-03-31 1964-11-03 Rca Corp Stereophonic phonograph system
US3178520A (en) * 1957-10-29 1965-04-13 Ronette Piezo Electrische Ind Binaural pick-up cartridge
US3215785A (en) * 1958-12-23 1965-11-02 Astatic Corp Stereophonic piezoelectric pickup cartridge
US3215786A (en) * 1959-08-21 1965-11-02 Astatic Corp Universal monaural-binaural phonograph pickup cartridge
US3225146A (en) * 1958-03-14 1965-12-21 Rca Corp Stereophonic phonograph system
US3231673A (en) * 1961-10-23 1966-01-25 Rca Corp Stereophonic subcarrier signal generator
US3236955A (en) * 1960-02-02 1966-02-22 Telefunken Ag Stereophonic electrodynamic transducer
US3261925A (en) * 1960-10-06 1966-07-19 Bernard Smith Lab Inc A Stereophonic photoelectric transducer
US3297831A (en) * 1964-02-06 1967-01-10 Walter O Stanton Magnetic stereophonic phonograph pickup
US3309469A (en) * 1958-02-27 1967-03-14 Rca Corp Phonograph pickup
US3360616A (en) * 1962-08-02 1967-12-26 Nippon Columbia Stereophonic ribbon cartridge
US3381149A (en) * 1958-03-03 1968-04-30 Electro Voice Multichannel piezoelectric transducer
US3463889A (en) * 1957-10-30 1969-08-26 Shure Bros Moving magnet stereophonic pickup
US3489864A (en) * 1965-03-08 1970-01-13 Electro Voice Stereo phonograph pickup and turnover mechanism
US3576956A (en) * 1958-06-20 1971-05-04 Philips Corp Stereophonic phonograph transducer
US3627931A (en) * 1968-01-23 1971-12-14 Nippon Columbia Moving magnet type stereo pickup
US4061889A (en) * 1973-10-09 1977-12-06 Gabor Erdelyi Film with light sound track carrying the stereophonic sound information; ribbon light valve for providing the light sound track as well as light sound adapter for reproducing the information recorded on
US4121059A (en) * 1975-04-17 1978-10-17 Nippon Hoso Kyokai Sound field expanding device
US4356349A (en) * 1980-03-12 1982-10-26 Trod Nossel Recording Studios, Inc. Acoustic image enhancing method and apparatus
US20060188101A1 (en) * 2003-07-21 2006-08-24 Fredrik Gunnarsson Audio stereo processing method, device and system
US7146010B1 (en) 1999-11-25 2006-12-05 Embracing Sound Experience Ab Two methods and two devices for processing an input audio stereo signal, and an audio stereo signal reproduction system
US20070237340A1 (en) * 2006-04-10 2007-10-11 Edwin Pfanzagl-Cardone Microphone for Surround-Recording
US20090175472A1 (en) * 2006-04-19 2009-07-09 Embracing Sound Experience Ab Loudspeaker Device

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE744615C (de) * 1941-03-07 1944-01-21 Philips Nv Mikrophon fuer geraeuschvolle Umgebung
US2498772A (en) * 1941-05-15 1950-02-28 Bendix Aviat Corp Aerial torpedo
US3002105A (en) * 1959-08-20 1961-09-26 Charles A Cady Emergency power supply
US5850453A (en) * 1995-07-28 1998-12-15 Srs Labs, Inc. Acoustic correction apparatus
US8050434B1 (en) 2006-12-21 2011-11-01 Srs Labs, Inc. Multi-channel audio enhancement system

Cited By (45)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2481911A (en) * 1942-05-20 1949-09-13 Hartford Nat Bank & Trust Co Device for adjusting the stereophonic effect in devices for stereophonic transmission
US2505585A (en) * 1944-12-23 1950-04-25 Us Sec War Electroacoustic binaural listening system
US2616970A (en) * 1948-02-11 1952-11-04 Hartford Nat Bank & Trust Co Device for the transmission by electrical means of oscillations of acoustic frequency
US2710662A (en) * 1948-12-23 1955-06-14 Armour Res Found Sound projection system
US2836662A (en) * 1954-08-18 1958-05-27 Emi Ltd Electrical sound transmission systems
US3070658A (en) * 1956-08-31 1962-12-25 Philips Corp Stereophonic sound collecting device
US3053943A (en) * 1957-07-12 1962-09-11 Columbia Broadcasting Syst Inc Phonograph record cutter
US3055989A (en) * 1957-08-12 1962-09-25 Columbia Broadcasting Syst Inc Ceramic reproducer
US3178520A (en) * 1957-10-29 1965-04-13 Ronette Piezo Electrische Ind Binaural pick-up cartridge
US3463889A (en) * 1957-10-30 1969-08-26 Shure Bros Moving magnet stereophonic pickup
US2958738A (en) * 1958-01-06 1960-11-01 Erie Resistor Corp Compensating network for binaural pickup
US3067292A (en) * 1958-02-03 1962-12-04 Jerry B Minter Stereophonic sound transmission and reproduction
US3309469A (en) * 1958-02-27 1967-03-14 Rca Corp Phonograph pickup
US3118978A (en) * 1958-02-27 1964-01-21 Gen Electric Magnetic stereophonic phonograph cartridge
US3381149A (en) * 1958-03-03 1968-04-30 Electro Voice Multichannel piezoelectric transducer
US3051798A (en) * 1958-03-05 1962-08-28 Fonofilm Ind As Device for the recording or reproduction of sound tracks
US3225146A (en) * 1958-03-14 1965-12-21 Rca Corp Stereophonic phonograph system
US3155779A (en) * 1958-03-31 1964-11-03 Rca Corp Stereophonic phonograph system
US3026378A (en) * 1958-04-30 1962-03-20 Rca Corp Stereophonic audio-frequency signal amplifier systems
US3013125A (en) * 1958-05-16 1961-12-12 Columbia Broadcasting Syst Inc Stereophonic recording
US3576956A (en) * 1958-06-20 1971-05-04 Philips Corp Stereophonic phonograph transducer
US3067295A (en) * 1958-08-04 1962-12-04 Pickering & Co Inc Stereophonic phonograph pick-up device
US3047666A (en) * 1958-10-27 1962-07-31 Murray G Crosby Compatible stereophonic system
US3215785A (en) * 1958-12-23 1965-11-02 Astatic Corp Stereophonic piezoelectric pickup cartridge
US3115554A (en) * 1959-01-02 1963-12-24 Philips Corp Stereo transducer
US3215786A (en) * 1959-08-21 1965-11-02 Astatic Corp Universal monaural-binaural phonograph pickup cartridge
US3083264A (en) * 1959-12-10 1963-03-26 Bell Telephone Labor Inc Sum and difference stereophonic transmission with negative feedback
US3236955A (en) * 1960-02-02 1966-02-22 Telefunken Ag Stereophonic electrodynamic transducer
US3117186A (en) * 1960-02-17 1964-01-07 Richard W Burden Compatible stereophonic broadcast system
US3086780A (en) * 1960-07-26 1963-04-23 Foster Mallard Ltd Sound reproducing machines
US3261925A (en) * 1960-10-06 1966-07-19 Bernard Smith Lab Inc A Stereophonic photoelectric transducer
US3231673A (en) * 1961-10-23 1966-01-25 Rca Corp Stereophonic subcarrier signal generator
US3360616A (en) * 1962-08-02 1967-12-26 Nippon Columbia Stereophonic ribbon cartridge
US3297831A (en) * 1964-02-06 1967-01-10 Walter O Stanton Magnetic stereophonic phonograph pickup
US3489864A (en) * 1965-03-08 1970-01-13 Electro Voice Stereo phonograph pickup and turnover mechanism
US3627931A (en) * 1968-01-23 1971-12-14 Nippon Columbia Moving magnet type stereo pickup
US4061889A (en) * 1973-10-09 1977-12-06 Gabor Erdelyi Film with light sound track carrying the stereophonic sound information; ribbon light valve for providing the light sound track as well as light sound adapter for reproducing the information recorded on
US4121059A (en) * 1975-04-17 1978-10-17 Nippon Hoso Kyokai Sound field expanding device
US4356349A (en) * 1980-03-12 1982-10-26 Trod Nossel Recording Studios, Inc. Acoustic image enhancing method and apparatus
US7146010B1 (en) 1999-11-25 2006-12-05 Embracing Sound Experience Ab Two methods and two devices for processing an input audio stereo signal, and an audio stereo signal reproduction system
US20060188101A1 (en) * 2003-07-21 2006-08-24 Fredrik Gunnarsson Audio stereo processing method, device and system
US7702111B2 (en) 2003-07-21 2010-04-20 Embracing Sound Experience Ab Audio stereo processing method, device and system
US20070237340A1 (en) * 2006-04-10 2007-10-11 Edwin Pfanzagl-Cardone Microphone for Surround-Recording
US20090175472A1 (en) * 2006-04-19 2009-07-09 Embracing Sound Experience Ab Loudspeaker Device
US8620010B2 (en) 2006-04-19 2013-12-31 Embracing Sound Experience Ab Loudspeaker device

Also Published As

Publication number Publication date
FR45642E (fr) 1935-11-02
FR45547E (fr) 1935-09-12
US2062275A (en) 1936-11-24
FR747504A (fr) 1933-06-16

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