EP0606387B1 - System zur tonaufnahme sowie gerät zur tonaufnahme und -wiedergabe - Google Patents

System zur tonaufnahme sowie gerät zur tonaufnahme und -wiedergabe Download PDF

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Publication number
EP0606387B1
EP0606387B1 EP92921887A EP92921887A EP0606387B1 EP 0606387 B1 EP0606387 B1 EP 0606387B1 EP 92921887 A EP92921887 A EP 92921887A EP 92921887 A EP92921887 A EP 92921887A EP 0606387 B1 EP0606387 B1 EP 0606387B1
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EP
European Patent Office
Prior art keywords
sound
phase shift
microphones
symmetry
signals
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP92921887A
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English (en)
French (fr)
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EP0606387A1 (de
Inventor
Frédéric Zurcher
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Prescom
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Prescom
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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
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/32—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only
    • H04R1/34—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by using a single transducer with sound reflecting, diffracting, directing or guiding means
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/32—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only
    • H04R1/40—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers
    • H04R1/406—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers microphones
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R27/00—Public address systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/005—Circuits for transducers, loudspeakers or microphones for combining the signals of two or more microphones
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
    • H04R2201/40—Details of arrangements for obtaining desired directional characteristic by combining a number of identical transducers covered by H04R1/40 but not provided for in any of its subgroups
    • H04R2201/401—2D or 3D arrays of transducers

Definitions

  • the present invention relates to a sound recording system.
  • the invention also relates to a sound pickup and restitution apparatus comprising such a system.
  • the present invention has a main application in the field of audio conferencing, in which a sound pickup and playback device is included in a single set of relatively small dimensions.
  • This assembly must be able to be placed easily on a table and operate in any room without the need for acoustic treatment of these premises.
  • this type of device does not fulfill conditions 2 (because of the 180 ° phase differences between speakers, the radiation pattern of the speaker assembly will not be circular in the horizontal plane and will depend significantly on the frequencies emitted) and 3 (because the microphone picks up both direct and indirect reflected sounds, which means that the quality of the sound picked up by the microphone depends too much largely from the position of the speaker in the room and the configuration of this room).
  • this system does not provide for configuration in the case where several microphones are used.
  • an important characteristic of this system is that, with each microphone, there is necessarily associated a loudspeaker and that the technique implemented requires that the sound signals picked up by the microphones be transmitted to the loudspeakers. associated. This arrangement constitutes a local sound system which is not desirable in so-called "hands-free" or audio conference devices.
  • a main object of the present invention is to provide a sound recording system which gives rise to low sensitivity to sounds arriving in a predetermined direction.
  • Another object of the invention is that, in a plane perpendicular to the predetermined direction, a sensitivity varying relatively little is obtained as a function of the direction from which the sounds originate and as a function of the frequency components of these sounds.
  • the present invention aims to provide a sound pickup system whose structure substantially prohibits the passage of vertical components to each microphone while leaving any possibility of processing the horizontal components.
  • the invention thus provides a sound recording system, comprising several sound reception devices, in number n greater than two and arranged, at regular intervals, on a circumference centered with respect to a direction of symmetry, and processing means to process the signals coming from the sound reception devices, these processing means being arranged to apply a phase shift of 360 ° / n between the signals coming respectively from any two adjacent sound reception devices and to add the signals thus phase shifted obtaining substantially uniform and undiminished reception of signals relating to components parallel to the P plane regardless of the direction of the waves and a substantially zero reception of the signals relating to the components parallel to the line of symmetry, sensed acoustic waves, characterized in that the sound reception devices comprise microphones arranged in the same plane perpendicular to the direction of symmetry, each microphone being housed in a cavity open on one side facing a flat plate reflecting the sound waves and arranged parallel to the plane P in which the sound receiving devices are located.
  • each microphone in a cavity open on one side facing a flat plate reflecting sound waves and arranged parallel to the plane in which the sound receiving devices are located, the vertical components of the sound signals cannot pass in each of the cavities and the horizontal components can be treated without difficulty.
  • the incident sounds in the direction of symmetry reach them in phase and with the same intensity. Consequently, due to the applied phase shifts and the addition of the phase-shifted signals, these incident sounds in the direction of symmetry are substantially eliminated after the processing.
  • the incident sounds perpendicular to the direction of symmetry reach the various reception devices with phase and / or amplitude differences between these devices. These sounds are therefore preserved and correctly taken into account.
  • this structure makes it possible to obtain a regular radiation diagram in a plane perpendicular to the direction of symmetry.
  • the invention provides a sound pickup and playback device, comprising sound pickup means and sound playback means comprising at least one speaker characterized in that said sound pickup means comprise a system according to the first object of the invention, with a direction of symmetry (D).
  • This device can be used for audio conferences and satisfies very satisfactorily the criteria, 1 to 4 listed at the beginning.
  • the apparatus comprises a housing 1, a body 2 in which are housed several devices for receiving sound M1, M2, M3, M4, and an element 3 in which is mounted a loudspeaker 4.
  • the body 2 and the element 3 have a general shape of revolution around a direction of symmetry D.
  • the element 3 is mounted on the body 2 which is itself mounted on the housing 1.
  • Des Phonically insulating, and / or mechanically damping materials such as 5, can be interposed between the element 3 and the body 2, or even between the body 2 and the upper part of the housing 1.
  • the device has a structure symmetrical around direction D to minimize the effect of mechanical vibrations which can affect the signals produced by microphones M1, M2, M3, M4.
  • the housing 1 has at its lower part feet 6 of rubber or the like for placing the device on a horizontal surface such as a table.
  • the direction of symmetry D is then vertical.
  • Electrical circuits 7, 8 are mounted inside the housing 1. These circuits can be connected as shown diagrammatically at 9, 10 in FIG. 1, to an external audio conference system, not shown, with which the device operates according to the invention. 'invention.
  • These circuits include an amplification circuit 7 which receives signals from the audio conference system and sends them in amplified form to the loudspeaker 4 so that the latter emits the corresponding sounds, and processing means 8 for processing the signals. from the M1, M2, M3, M4 sound reception devices and send them after processing to the audio conference system.
  • the amplification circuit 7 can include, to increase listening comfort, a cell electronic correction of the response curve of the loudspeaker 4, in particular to reinforce the low frequencies and to suppress possible resonances or anti-resonances.
  • conventional means of echo cancellation are generally mounted between circuits 7 and 8.
  • each sound reception device consisting of a single microphone M1, M2, M3, M4.
  • These four microphones M1, M2, M3, M4 are all arranged in the same horizontal plane P perpendicular to the direction of symmetry D.
  • the four microphones M1, M2, M3, M4 are distributed symmetrically with respect to the direction of symmetry D, which is perpendicular to the plane of Figure 2. These four microphones are located on a circumference 13 parallel to the plane P and centered on the direction of symmetry D. These four microphones are associated in pairs, respectively M1, M3 and M2, M4, the microphones of each pair being arranged symmetrically with respect to the direction of symmetries D, and the two pairs of microphones being arranged along two radial lines 14, 15 forming between them a right angle.
  • Each of the microphones M1, M2, M3, M4 is housed in a respective cavity 12 machined in the body 2.
  • This body 2 is metallic, for example made of brass. It is traversed by an axial bore 16 in the direction of symmetry D, and it further comprises four radial bores 17, each extending between the axial bore 16 and one of the four cavities 12.
  • the axial bore 16 serves the passage of the connection wires (not shown) of the loudspeaker 4 to the amplification circuit 7, with a corresponding bore 18 provided at the base of the element 3.
  • the axial bore 16 and the four radial bores 17 are used for the passage of the connection wires (not shown) of the microphones M1, M2, M3, M4, to the processing means 8 located in the housing 1.
  • the four microphones M1, M2, M3, M4 are of the condenser type, and have a small dimension (for example a cylindrical shape with a diameter of 6 mm, and a height of 4.5 mm). It is known that, for a given production series, such microphones have substantially the same response curve, with an offset between them not exceeding 3 to 4 decibels. To make the device, it is therefore easy to sort four microphones having identical response curves to within a predetermined tolerance (for example 0.5 decibel).
  • the body 2 is mounted on a flat metal plate 20, parallel to the plane P of the microphones and constituting the upper face of the housing 1.
  • the cylindrical body 2 has an axial cylindrical extension 21, of smaller diameter which rests on this flat plate 20 and which defines a spacing 22 between the flat plate 20 and the surface 23 of the body 2 which is parallel to the plane P, and on which the machined cavities open 12.
  • the extension 21 of the body 2 provides a certain acoustic insulation between the microphones M1 , M2, M3, M4 vis-à-vis the sounds arriving in a plane perpendicular to the direction of symmetry D. As can be seen in FIG.
  • the cavities 12 have an axial height greater than the height of the cylinders of the microphones M1 , M2, M3, M4, and the latter are pressed into their respective cavities 12 so as to leave a gap 24 between the side of each microphone facing the plate 20 and the surface 23 defining the bor d of the cavities 12.
  • each cavity 12 extends into a portion 25 of diameter weaker which defines a shoulder against which the rear face of the microphone rests, and into which the radial bore 17 opens, thus giving space for the connection wires not shown.
  • the element 3 mounted above the body 2 forms a resonance box for the loudspeaker 4.
  • the loudspeaker 4 is mounted in the element 3 in the direction of symmetry D, and oriented in this direction of symmetry D , opposite the plane P where the microphones M1, M2, M3, M4 are located.
  • the membrane 29 of the speaker 4 which has a shape of revolution around an axis, is arranged in the element 3 so that this axis coincides with the direction of symmetry D of the device, the edge outer 30 of this membrane 29 being located in a plane perpendicular to the direction of symmetry D.
  • this outer edge 30 of the membrane 29 is typically between 100 and 150 mm above the horizontal surface on which the device is placed.
  • a protective grid 32 is mounted at the top of the element 3 to protect the membrane 29 of the loudspeaker 4.
  • the external peripheral surface 33 of the element 3 has a concave curvature and is tangentially connected to the external peripheral surface of the body 2, this external peripheral surface of the body 2 being a cylinder defined by generatrices substantially parallel to the direction of symmetry D.
  • the processing means 8 for the signals from the microphones M1, M2, M3, M4 are shown diagrammatically in FIG. 3. These processing means comprise on the one hand two differential preamplifiers A13, A24 and two phase shift channels D13, D24 for applying a phase shift between the signals from different microphones respectively, and on the other hand an adder circuit 40 provided for summing the phase-shifted signals coming from the phase-shifting channels D13, D24. At the output of the adder circuit 40 is mounted a circuit 41 which formats the signals with a view to their transmission to the external audio conference system.
  • the phase shifts applied and the addition carried out are such that the signals relating to any sound wave arriving in phase and with the same intensity on each of the microphones M1, M2, M3, M4 are substantially canceled at the output of the circuit. adder 40.
  • the sounds emitted by the speaker 4 and reflected by the horizontal ceiling located above the device reach the four microphones in the direction of symmetry D and have, taking into account the symmetrical arrangement of the microphones, an identical phase and intensity on each of the microphones. Consequently, these reflected signals are advantageously eliminated from the output signal from the processing circuit 8.
  • the symmetrical structure of the sound pickup system ensures that the mechanical vibrations of the device will reach each of the microphones in an identical manner. Consequently, the effect of these vibrations on the microphones is also eliminated from the output signal of the processing circuit 8.
  • a differential preamplifier A13 (respectively A24) has two inputs E1, E3 (respectively E2, E4) each connected to one of the microphones M1, M3 (respectively M2, M4) of a pair of microphones arranged in diametrically opposite position with respect to the direction of symmetry D.
  • the differential preamplifiers A13, A24 preamplify the output signals of the microphones, eliminating certain parasites present in these output signals, and produce output signals S13 and S24 which are proportional to the difference between the input signals they receive from microphones.
  • each differential preamplifier A13 applies a phase shift of 180 ° between the signals from the microphones M1, M3 (respectively M2, M4) and adds the signals thus phase shifted, which substantially cancels the signals relating to any sound wave arriving in phase and with the same intensity on each of the microphones M1, M3 (respectively M2, M4) constituting the pair.
  • the outputs of the differential preamplifiers A13, A24 are respectively connected to the inputs of two phase shift channels D13, D24.
  • the phase shifting channel D13 receives the output signal S13 from the differential preamplifier A13 and applies to it a frequency-dependent phase shift to transmit an output signal SD13.
  • phase shifting channel D24 receives the output signal S24 from the differential preamplifier A24, and applies to it a frequency dependent phase shift to transmit an output signal SD24. Even if the output signals SD13 and SD24 have individually received a frequency-dependent phase shift, the phase shift channels D13, D24 are arranged so that their respective output signals SD13, SD24 have between them a phase shift relatively independent of the frequency. In the example with four microphones described here, this phase shift independent of the frequency is equal to 90 °.
  • the phase shifted output signals SD13, SD24 are sent to two inputs of the adder circuit 40.
  • the latter sends an output signal ST equal to the sum of these two signals SD13, SD24.
  • This sum ST is therefore a combination of the signals from the four microphones M1, M2, M3, M4 in which a phase shift of 90 ° exists between the signals from respectively two microphones any adjacent. In this combination, therefore, the contributions of the sounds reaching the microphones in the direction of symmetry D and the effects of symmetrical mechanical vibrations are eliminated.
  • this combination ST takes homogeneous account of the sound signals, whatever their direction of incidence in this plane.
  • the sounds emitted by speakers are thus taken into account satisfactorily whatever the position of these speakers relative to the device, while the echoes from the loudspeaker. speaker are substantially eliminated.
  • the arrangement of the microphones M1, M2, M3, M4 in the body 2 and the presence of the pressure zones between this body 2 and the metal plate 20 reflecting the sound waves largely eliminate the indirect echoes reaching the microphones.
  • the cylindrical body 2 has an outside diameter of 54 mm
  • the four microphones are placed on a circumference 13 of diameter 46 mm
  • the extension 21 of the body 2 has a diameter of 36 mm and an axial height d 'about 2 mm defining the spacing 22
  • the cavities 12 have a diameter of 6.mm coinciding with that of the microphones and an axial height allowing to leave an interval 24 of about 3 mm.
  • the variation of the total combined signal for all the microphones as a function of the direction of incidence in a plane perpendicular to the direction of symmetry D is only ⁇ 0.5 decibel in the entire frequency band. corresponding to telephone frequencies. If this possible frequency band is widened up to 7000 hertz, there is only a variation of ⁇ 2.5 decibels, which can be further reduced by decreasing the dimensions of the assembly mounting microphones.
  • the detailed structure of the differential preamplifier A13 is shown in FIG. 4, it being understood that the differential amplifier A24 has an identical structure.
  • the inputs E1, E3 of the differential preamplifier A13 are each connected to the positive input terminal of an operational amplifier 45, 46, and are moreover connected to each other by two resistors 47, 48 connected in series and having the same ohmic value .
  • the connection point of these two identical resistors 47, 48 is connected to ground.
  • the negative input terminals of the operational amplifiers 45, 46 are connected together by a resistor r.
  • Each of the two operational amplifiers 45, 46 has its output terminal connected by a feedback resistor R to its negative input terminal.
  • the differential preamplifier A13 comprises a third operational amplifier 49, the output of which delivers the output signal S13 from the differential preamplifier A13.
  • the positive input terminal of this third operational amplifier 49 is connected via a resistor 50 to the output terminal of the operational amplifier 45, the positive input terminal of which is connected to the microphone M1.
  • the negative input terminal of the third operational amplifier 49 is connected, via a resistor 51 having the same ohmic value as the resistor 50 above, to the output terminal of the operational amplifier 46 including the terminal d the positive input is connected to the microphone M3.
  • the positive input terminal of the third operational amplifier 49 is also connected to ground via a resistor 52 having the same ohmic value as the above-mentioned resistors 50, 51.
  • the output terminal of the third operational amplifier 49 is further connected to its negative input terminal by a feedback resistance 53 having the same ohmic value as the above resistors 50, 51, 52.
  • FIG. 4 does not represent the power supplies of the microphones M1, M3 and the operational amplifiers 45, 46, 49.
  • This assembly of the differential preamplifier A13 represented in FIG. 4, achieves the desired difference between the output signals of the microphones M1, M3, by additionally eliminating the parasites present jointly in these signals.
  • the preamplification gain can be chosen as large as desired by choosing the 2R / r ratio.
  • phase shift channels D13, D24 are shown diagrammatically in FIG. 7.
  • Each of these phase shift channels D13, D24 consists of an association in alternating series of all-pass cells of a first type PT1 (FIG. 5) and of a second type PT2 ( Figure 6), each all-pass cell having a gain equal to 1, regardless of the frequency of the voltage signals applied.
  • an all-pass cell PT1 has its input connected on the one hand to the negative input terminal of an operational amplifier OA1 by means of a resistance of ohmic value r 1 , and d on the other hand to the positive input terminal of this operational amplifier OA1 by means of a resistance of ohmic value R 1 .
  • the output of the all-pass cell PT1 is constituted by the output terminal of the operational amplifier OA1, which is connected to its negative input terminal by a feedback resistor of ohmic value r 1 .
  • the positive input terminal of the operational amplifier OA1 is also connected to ground via a capacitor of capacity C 1 .
  • This all-pass cell PT1 introduces between its output and input signals a phase shift depending on the frequency of the input signal and between 0 ° for a frequency tending towards zero and 180 ° for a frequency tending towards infinity.
  • an all-pass cell of the PT2 type has its input connected on the one hand to the negative input terminal of an operational amplifier OA2 by means of a resistance of ohmic value r 2 , and on the other hand to the positive input terminal of this operational amplifier OA2 by means of a capacitor of capacitance C 2 .
  • the output of the all-pass cell PT2 is constituted by the output terminal of the operational amplifier OA2 which is connected to its negative input terminal by means of a feedback resistor having an ohmic value r 2 .
  • the positive input terminal of this operational amplifier OA2 is also connected to ground via a resistor with an ohmic value R 2 .
  • the PT2 cell introduces between its output and input signals a phase shift depending on the frequency of the input signal and between 180 ° for a frequency tending towards zero and 360 ° for a frequency tending towards infinity.
  • the phase shift channel D13 successively comprises a all-pass cell PT1A of the PT1 type, a all-pass cell PT2B of the PT2 type, and a all-pass cell PT1C of the PT1 type.
  • the phase shift channel D24 successively comprises a PT2A all-pass cell of PT2 type, a PT1B all-pass cell of PT1 type, and a PT2C all-pass cell of PT2 type.
  • the all-pass cells PT1A, PT2B, PT1C or PT2A, PT1B, PT2C associated in series in each phase shift channel D13, D24 comprise at least one set of all-pass cells which, considered in ascending order of their frequencies reference, are alternately of the first PT1 and of the second type PT2 and have reference frequencies in geometric progression according to an identical reason K for the two phase shift channels D13, D24.
  • FIGS. 8 to 11 are sectional views similar to FIG. 2.
  • six microphones 100 are used which are arranged geometrically at the vertices of a regular hexagon centered on the direction of symmetry D. These six microphones 100 can also be associated in pairs, each consisting of two diametrically opposed microphones relative to direction D, the output signals of the two microphones of each pair being subtracted from each other as described above.
  • the phase shifting channels are then arranged to apply a 60 ° phase shift between the signals obtained by subtraction relative to each pair of microphones 100, which makes it possible to obtain substantially the same advantages as in the example with four microphones described with reference to the figures. 1 to 7.
  • n pairs of sound receiving devices can be provided at regular intervals along a circumference 13 centered on the direction of symmetry D, n denoting an integer at least equal to two, the processing means 8 then being arranged to apply a phase shift of 360 ° / 2n between the signals originating respectively from any two adjacent sound reception devices.
  • the metal body 102 in which the cavities 112 receiving the various are machined microphones 100 may have a general shape different from the cylindrical shape described above.
  • the diameter of the lower extension 121 of the body 102 is kept over the entire height of the body 102, and the latter comprises, in its part located above the extension 121, six radial protrusions in which the six are respectively machined. cavities 112 receiving the microphones 100.
  • the pressure zones defined between the metal upper plate 20 of the housing 1 and the part of the body 102 receiving each microphone 100 are defined spatially more clearly.
  • Another possible variant of the geometric shape of the body 202 is constituted by the example with four microphones M1, M2, M3, M4 shown in FIG. 9.
  • the part of the body 202 located above its lower extension 221 has a regular polygonal shape centered on the direction of symmetry D, the circular outline of the extension 221 being part of this regular polygon (this polygon is a square in an example with four microphones).
  • the cavities receiving the microphones M1, M2, M3, M4 are then machined in the parts of the square which extend outside the circular shape defined by the extension 221.
  • each sound pick-up device 300 consists of several microphones 301 (two in the example shown), located close to each other.
  • the body 302 therefore comprises eight cavities arranged symmetrically with respect to the direction of symmetry D to receive the eight microphones 301.
  • the processing means 8 then comprise four additional adder circuits (not shown) for add in phase the two signals respectively from the two microphones 301 making up each of the sound reception devices 300.
  • the rest of the processing means 8 is identical to what has been described with reference to FIG. 3, the output signals of the four additional adder circuits then constituting the four signals addressed to the inputs of the differential preamplifiers A13, A24.
  • the method according to the present invention can be implemented with an odd number (three) of microphones 400.
  • the three microphones are then located in the body 402 along three concurrent radial lines at their intersection with the direction of symmetry D and forming between them angles of 120 °.
  • the processing means 8 do not include differential preamplifiers mounted immediately at the output of the microphones 400. It is necessary to use phase-shifting channels applying a phase shift of 120 ° between the signals from any two microphones 400, before adding the signals thus out of phase.
  • FIG 12 there is shown in schematic elevation an alternative construction of the recording device and sound reproduction according to the invention.
  • the base of the device is constituted by the box 501 containing the various electrical circuits of the device.
  • the apparatus comprises a main loudspeaker 504 oriented in the direction of symmetry D and a smaller auxiliary loudspeaker 505 dimension (tweet).
  • the two speakers 504, 505 are arranged back to back so as to transmit in opposite directions in the direction D.
  • the plane P in which the microphones M1 to M4 are located extends between the two speakers 504, 505, so that the microphones receive practically no direct sound from the speakers 504, 505.
  • the element 503 forming a resonance box for the main speaker 504 has a generally cylindrical shape centered on the direction of symmetry D and is mounted on the housing 501 by means of four uprights 519, through which the connection wires of the speakers 504, 505 and the microphones pass.
  • a cone-shaped element 511 is fixed to the upper face of the housing 501, the cone being of revolution around the direction of symmetry D and pointing towards the main speaker 504.
  • the main speaker 504 is oriented downwards towards the cone 511 and the sounds it emits are therefore reflected laterally by the cone 511, with a regular distribution in a horizontal plane.
  • the body 502 in which the microphones are housed is disposed on the side opposite to the cone-shaped element 511 with respect to the main speaker 504.
  • the arrangement of the microphones in the body 502 is similar to that described with reference to the figures 1 and 2, with a flat metal plate reflecting the sound waves 510 separating the element 503 forming a sound box for the main speaker 504 and the block 502 receiving the microphones.
  • the processing of the microphone signals is identical to that described above.
  • the auxiliary speaker 505 is mounted in an element 506 forming a sound box.
  • This element 506 is of frustoconical shape of revolution around the direction of symmetry D. Its side of smaller section is fixed to the upper part of the body 502 receiving the microphones, and its larger section side, like the 505 tweeter, faces up.
  • This arrangement illustrated in FIG. 12 provides an excellent efficiency of the main speaker 504 because the cone 511 directs the sound homogeneously towards the listeners.
  • the efficiency of the microphones is improved because they are located towards the upper part of the apparatus so that, when the latter is placed on a table, the microphones are placed at a higher level (for example 30 cm) to that of the table, that is to say at a level advantageously close to the mouths of the speakers when they are seated around the table.
  • the presence of an acute auxiliary speaker improves the quality of sound reproduction.

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  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • General Health & Medical Sciences (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Signal Processing Not Specific To The Method Of Recording And Reproducing (AREA)
  • Fittings On The Vehicle Exterior For Carrying Loads, And Devices For Holding Or Mounting Articles (AREA)
  • Input Circuits Of Receivers And Coupling Of Receivers And Audio Equipment (AREA)
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  • Stereophonic System (AREA)

Claims (16)

  1. Einrichtung zur Tonaufnahme mit mehreren Tonempfangsvorrichtungen (M1 bis M4; 100; 300; 400), deren n-Anzahl höher als zwei ist und die in gleichmäßigen Abständen über einen Umfang (13) zentrisch zu einer Symmetrierichtung (D) angeordnet sind, und mit Verarbeitungsmitteln (8) zur Verarbeitung von aus den Tonempfangsvorrichtungen entstandenen Signalen, wobei diese Verarbeitungsmitteln (8) derart ausgebildet sind, daß eine Phasenverschiebung von 360°/n zwischen den jeweils aus zwei beliebigen benachbarten Tonempfangsvorrichtungen entstandenen Signalen ansteht und daß die so phasenverschobenen Signale zusammen addiert werden, um einen wesentlich gleichmäßigen und nicht abgeschwächten Empfang von auf die zu der Ebene (P) parallelen Komponenten bezogenen Signalen unabhängig von der Wellenrichtung und einen wesentlichen Nullempfang der auf die zu der Symmetriegerade (D) parallelen Komponenten bezogenen Signalen der akustischen aufgefangenen Wellen zu ermöglichen, dadurch gekennzeichnet, daß die Tonempfangsvorrichtungen Mikrophone (M1, M2, M3, M4; 100; 301; 400) umfassen, die in einer zur der Symmetrierichtung (D) senkrechten gleichen Ebene (P) angeordnet sind, wobei jedes Mikrophon in einer Ausnehmung (12; 112) gelagert ist, die auf einer Seite (23) offen ist, die einer ebenen Platte (20; 510) gegenübersteht, die die Tonwellen reflektiert und parallel zu der Ebene (P) angeordnet ist, in welcher die Tonempfangsvorrichtungen sich befinden.
  2. Einrichtung nach Anspruch 1, dadurch gekennzeichnet, daß die Ausnehmungen (12 ; 112), in welchen die verschiedenen Mikrophone (M1 bis M4; 100; 301; 400) gelagert sind, in einem Körper (2; 102; 202; 302; 402; 502) angebracht sind, der eine zu der besagten Symmetrierichtung (D) symmetrische Form hat und seitens der die Tonwellen reflektierenden ebenen besagten Platte (20; 510) eine Verlängerung (21; 121; 221) aufweist, um einen bestimmten Abstand (22) zwischen den Ausnehmungen (12; 112) und der besagten Platte (20; 510) zu definieren.
  3. Einrichtung nach einem der Ansprüche 1 oder 2, dadurch gekennzeichnet, daß jedes Mikrophon (M1 bis M4; 100; 300; 400) in seine jeweilige Ausnehmung (12; 112) derart hineingedrückt wird, daß eine Spalte (24) zwischen einer Seite dieses der die Tonwellen reflektierenden ebenen Platte (20; 510) entgegengesetzten Mikrophons und einem der besagten Platte (20; 510) gegenüberstehenden Rand (23) dieser Ausnehmung (12; 112) gebildet wird.
  4. Einrichtung nach irgendeinem der vorgehenden Ansprüche 1 bis 3, dadurch gekennzeichnet, daß jede Tonempfangsvorrichtung ein einziges Mikrophon (M1 bis M4; 100; 300; 400) umfaßt.
  5. Einrichtung nach irgendeinem der vorgehenden Ansprüche 1 bis 3, dadurch gekennzeichnet, daß jede Tonempfangsvorrichtung (300) sich aus mehreren Mikrophonen (301) besteht, und daß die Verarbeitungsmitteln (8) zum phasenmäßigen Addieren der Signale ausgebildet sind, die jeweils aus den Mikrophonen (301) entstehen, die jede Tonempfangsvorrichtung (300) bilden, um den Ausgangssignal dieser Tonempfangsvorrichtung (300) zu erstellen.
  6. Einrichtung nach einem der Ansprüche 1 bis 5, wobei diese Einrichtung bei auf einer Umfang 13 mit einem Durchmesser von ca. 46 mm angeordneten 2N Mikrophonen ein kombiniertes Gesamtsignal für die Gesamtmikrophone aufweist, das schwach in Abhängigkeit von der Einfallrichtung in einer zur der Symmetrierichtung (D) senkrechten Ebene in dem gesamten Frequenzband veränderbar ist, das den telefonischen Frequenzen entspricht, und dessen Veränderung zunimmt, wenn dieses Frequenzband sich bis 7.000 Hertz erstreckt, dadurch gekennzeichnet, daß man die Veränderungen dieses Signals in dem oberen Teil dieses Frequenzbandes durch Reduzierung der Abmessungen des gesamten Aufbaus der Mikrophone weiter einschränken kann.
  7. Einrichtung nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß die besagten Tonempfangsvorrichtungen (M1 bis M4; 100; 300; 400) eine gerade Anzahl m = 2n aufweisen, die höher als drei ist, daß sie paarweise einander zugeordnet sind, daß die Tonempfangsvorrichtungen jedes der besagten Paare symmetrisch zu der Symmetrierichtung (D) angeordnet sind, daß die Verarbeitungsmittel (8) so ausgebildet sind, daß die jeweils aus den Empfangsvorrichungen jedes Paares entstandenen Signale voneinander abgezogen werden, um sie mit einer Phasenverschiebung von 180° miteinander zu addieren, daß eine Phasenverschiebung an jedes aus einem Paar entstandene Signal (S13, S14) angelegt wird, um eine Phasenverschiebung von 360°/m zwischen den Signalen zu schaffen, die jeweils aus zwei Paaren von beliebigen benachbarten Tonempfangseinrichtungen entstanden sind und daß die so phasenverschobenen Signale addiert werden.
  8. Einrichtung nach Anspruch 7, dadurch gekennzeichnet, daß die Verarbeitungsmitteln (8) für jedes Paar von Tonempfangseinrichtungen (M1 bis M4; 100; 300; 400) einen Differenzverstärker (A13 und A24) umfassen, der zwei Eingänge (E1, E3 und E2, E4) zur jeweiligen Aufnahme der aus den beiden Tonempfangseinrichtungen (M1 bis M4; 100; 300; 400) des Paares entstandenen Signale und einen Ausgang aufweist, der die verstärkte Differenz (S13 und S24) zwischen den an den Eingängen (E1 bis E4) entgegengenommenen Signalen liefert.
  9. Einrichtung nach einem der Ansprüche 7 oder 8, dadurch gekennzeichnet, daß die Verarbeitungsmitteln (8) zur Anlegung der 360°/m-Phasenverschiebung zwischen den jeweils aus zwei beliebigen benachbarten Tonempfangseinrichtungen entstandenen Signalen n Phasenschieber-Kanäle (D13, D24) umfassen, die jeweils einen ein aus einem der besagten Paare entstandenes Signal (S13, S24) aufnehmenden Eingang und einen Ausgang (SD13, SD24) aufweisen, wobei die n Ausgänge der Phasenschieber-Kanäle addiert werden, um das aus der Einrichtung zur Tonaufnahme entstandene Signal herzustellen.
  10. Einrichtung nach Anspruch 9, dadurch gekennzeichnet, daß jeder Phasenschieber-Kanal (D13, D24) eine Serienverbindung von mehreren Allpaßzellen (PT1A, PT2B, PT1C; PT2A, PT1B, PT2C), die zu zwei Typen von Allpaßzellen (PT1, PT2) gehören, daß ein erster Typ von Allpaßzellen (PT1) einen Widerstand (R1) und eine Kapazität (C1) aufweist, deren Werte die Abhängigkeit einer elementaren Phasenverschiebung bestimmen, die durch die Allpaßzelle (PT1) zwischen ihrem Ausgangssignal und ihrem Eingangssignal nach der Frequenz ihres Eingangssignals geleistet wird, wobei diese elementare Phasenverschiebung zwischen 0° und 180° liegt und bei einer Bezugsfrequenz f1 = 1/(2ηR1C1) der Allpaßzelle (PT1) wesentlich 90° entspricht, daß ein zweiter Typ von Allpaßzellen (PT2) einen Widerstand (R2) und eine Kapazität (C2) aufweist, deren Werte die Abhängigkeit einer elementaren Phasenverschiebung bestimmen, die durch die Allpaßzelle (PT2) zwischen ihrem Ausgangssignal und ihrem Eingangssignal nach der Frequenz ihres Eingangssignals geleistet wird, wobei diese elementare Phasenverschiebung zwischen 180° und 360° liegt und bei einer Bezugsfrequenz f2 = 1/(2ηR2C2) der Allpaßzelle (PT2) wesentlich 270° entspricht, daß die serienmäßig verbundenen Allpaßzellen in jedem Phasenschieber-Kanal (D13, D14) wenigstens eine Einheit von Allpaßzellen (PT1A, PT2B, PT1C; PT2A; PT1B, PT2C) aufweisen, die von ihren steigenden Frequenzen ausgehend abwechselnd vom ersten (PT1) und zweiten Typ (PT2) sind und Bezugsfrequenzen (F, KF, K2F; G, KG, K2G) haben, die sich wesentlich gemäß einem identischen Verhältnis (K) für beide Phasenschieber-Kanäle (D13, D24) geometrisch abstufen.
  11. Einrichtung nach Anspruch 10, dadurch gekennzeichnet, daß das Verhältnis (K) der geometrischen Abstufungen etwa bei eη liegt.
  12. Einrichtung nach einem der Ansprüche 10 oder 11, dadurch gekennzeichnet, daß zwei Allpaßzellen (PT1A, PT2A) verschiedener Typen, die zu zwei unterschiedlichen Phasenschieber-Kanälen (D13, D14) gehören, jeweilige Bezugsfrequenzen (F, G) haben, deren Verhältnis (G/F) wesentlich K1-(d/180) entspricht, wobei K das Verhältnis der geometrischen Abstufungen und d einen vorbestimmten Wert bezeichnen, der in Grad ausgedrückt und einer erwünschten Differenz zwischen den Phasenverschiebungen (D1, D2) gleich ist, die jeweils von den beiden Phasenschieber-Kanälen (D13, D24) angelegt wird.
  13. Einrichtung nach einem der Ansprüche 10 bis 12, dadurch gekennzeichnet, daß die Allpaßzellenanzahl pro Phasenschieber-Kanal (D13, D24) sich auf drei beläuft.
  14. Einrichtung nach einem der Ansprüche 1 bis 13, dadurch gekennzeichnet, daß sie eine allgemeine symmetrische Struktur um die Symmetrierichtung (D) aufweist.
  15. Gerät zur Tonaufnahme und -wiedergabe mit Mitteln zur Tonaufnahme und Mitteln zur Tonwiedergabe, die wenigstens einen Lautsprecher (4; 504, 505) umfassen, dadurch gekennzeichnet, daß die besagten Mittel zur Tonaufnahme eine Einrichtung nach einem der Ansprüche 1 bis 14 mit einer Symmetrierichtung (D) aufweisen.
  16. Gerät zur Tonaufnahme und -wiedergabe nach Anspruch 15, dadurch gekennzeichnet, daß die besagten Mittel zur Tonwiedergabe an der Symmetrieachse (D) derart angeordnet sind, daß das besagte Gerät zur Tonaufnahme und -wiedergabe eine allgemeine symmetrische Struktur um die besagte Symmetrierichtung (D) aufweist.
EP92921887A 1991-10-02 1992-10-02 System zur tonaufnahme sowie gerät zur tonaufnahme und -wiedergabe Expired - Lifetime EP0606387B1 (de)

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FR9112125 1991-10-02
FR9112125A FR2682251B1 (fr) 1991-10-02 1991-10-02 Procede et systeme de prise de son, et appareil de prise et de restitution de son.
PCT/FR1992/000919 WO1993007730A1 (fr) 1991-10-02 1992-10-02 Procede et systeme de prise de son, et appareil de prise et de restitution de son

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DE69213748D1 (de) 1996-10-17
AU669859B2 (en) 1996-06-27
EP0606387A1 (de) 1994-07-20
CA2120019C (en) 2000-05-30
ATE142836T1 (de) 1996-09-15
ES2094374T3 (es) 1997-01-16
JP3099961B2 (ja) 2000-10-16
CA2120019A1 (en) 1993-04-15
FR2682251B1 (fr) 1997-04-25
JPH06511363A (ja) 1994-12-15
RU2096928C1 (ru) 1997-11-20
DE69213748T2 (de) 1997-04-10
WO1993007730A1 (fr) 1993-04-15
US5524059A (en) 1996-06-04
FR2682251A1 (fr) 1993-04-09
AU2777992A (en) 1993-05-03

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