EP0692921A1 - Schallaufnahmevorrichtung durch Elektretmikrofon - Google Patents

Schallaufnahmevorrichtung durch Elektretmikrofon Download PDF

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Publication number
EP0692921A1
EP0692921A1 EP95401674A EP95401674A EP0692921A1 EP 0692921 A1 EP0692921 A1 EP 0692921A1 EP 95401674 A EP95401674 A EP 95401674A EP 95401674 A EP95401674 A EP 95401674A EP 0692921 A1 EP0692921 A1 EP 0692921A1
Authority
EP
European Patent Office
Prior art keywords
electret microphone
input
differential
preamplifier stage
symmetrical
Prior art date
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.)
Granted
Application number
EP95401674A
Other languages
English (en)
French (fr)
Other versions
EP0692921B1 (de
Inventor
Grégoire Le Tourneur
Marcel Clement
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Orange SA
Original Assignee
France Telecom SA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by France Telecom SA filed Critical France Telecom SA
Publication of EP0692921A1 publication Critical patent/EP0692921A1/de
Application granted granted Critical
Publication of EP0692921B1 publication Critical patent/EP0692921B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/04—Microphones
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/02—Casings; Cabinets ; Supports therefor; Mountings therein
    • H04R1/04—Structural association of microphone with electric circuitry therefor
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/01—Electrostatic transducers characterised by the use of electrets
    • H04R19/016—Electrostatic transducers characterised by the use of electrets for microphones

Definitions

  • the invention relates to a sound pickup device by electret microphone.
  • the final cost of the product essentially depends on the type of microphone used, the cost of this varying directly as a result of its quality.
  • the overall cost can become very high.
  • Dynamic microphones are generally used for sound recording in shows and in the studio, because of their very high quality, but their high price and their irreducible size do not make them suitable for sound recording for telephone terminals, or any making sound economic.
  • Electret microphones providing a weak useful signal, require a preamplifier in order to bring the output signal of the electret capsule at a level of the order of a volt.
  • the electret capsule must be supplied with electrical energy, since it incorporates a field effect transistor.
  • the electret microphone M comprising a point connected to ground and a point receiving the electrical supply and delivering the useful audio signal, the usual arrangement is shown in FIG. 1a.
  • the output level of the useful signal which varies from a few hundred microvolts to a few tens of millivolts, depending on the sensitivity of the capsules and the position of the microphone relative to the source, i.e.
  • this mounting requires the implementation of a high gain preamplification stage.
  • the presence of this significant gain makes the assembly very sensitive to power supply noise and electromagnetic disturbances. Indeed, if the supply voltage VM is not perfectly regulated, the variations thereof are seen as a useful signal by the preamplification stage. The same is true for electromagnetic radiation or parasites, which affect the useful input of the preamplification stage.
  • Such sound recording systems are said to be noisy, because these, on the one hand, have a low signal-to-noise ratio when the power supply is not perfectly regulated, rate of change less than or equal to 0.5% , and, on the other hand, are very sensitive to parasitic electromagnetic radiation, 50 Hz, if the assembly is not perfectly shielded.
  • the object of the present invention is to remedy the aforementioned drawbacks by using a device for picking up sound by an electret microphone of the differential type in which any transformer is omitted.
  • Another object of the present invention is also the implementation of a sound pickup device by good quality electret microphone, due to its operation in differential mode.
  • the device for taking sound from an electret microphone, object of the present invention in which signals delivered by the electret microphone are amplified by means of a differential preamplifier stage, is remarkable in that it comprises a link by connection capacity between each output terminal of the electret microphone and an input of the differential preamplifier stage.
  • a symmetrical bias circuit of the output terminals an electret microphone is provided, which comprises a first and a second voltage source, symmetrical with respect to a reference voltage, and each connected to an output terminal of the electret microphone.
  • the electret microphone sound pickup device finds application in the production of quality sound pickup systems in the field of telecommunications, voice recognition, acoustic antennas.
  • FIG. 2 it is indicated that the same references indicate the same elements as in FIGS. 1a and 1b relating to the prior art.
  • the sound pickup device comprises, as shown in FIG. 2 above, a link 1 per link capacity between each output terminal of the electret microphone M and an input of the differential preamplifier stage 3.
  • the link capacities bear the reference 11 and 12 on the figure 2.
  • a symmetrical bias circuit of the output terminals of the electret microphone M is provided, this circuit bearing the reference 2 in the aforementioned FIG. 2.
  • first 21 and a second 22 voltage source the voltages supplied by the sources 21 and 22 being symmetrical with respect to a reference voltage of the device, the mass of the sound pickup device.
  • Each voltage source 21, 22 is connected via a resistor 210, respectively 220, to an output terminal of the electret microphone M.
  • the polarization device 2 must be symmetrical, the supply voltages -VM and + VM delivered by sources 21 and 22 being opposite, resistors 210 and 220 and capacitors 11 and 12 being identical, for rejection in common mode.
  • the differential preamplifier stage 3 can advantageously comprise on each input channel a preamplifier device in non-differential mode, carrying the reference 30 respectively 31.
  • the preamplifiers in non-differential mode 30 and 31 can conventionally include a positive terminal forming an input terminal for the signals delivered by the connection capacitors 11 respectively. 12, and a resistive feedback coupling via resistors 301 and 311 respectively on the corresponding negative terminal.
  • the output resistors 302 and 312 make it possible to drive a differential output amplifier 32, which can conventionally include a positive terminal forming an input terminal connected to the output of the preamplifier 31 via a resistor 321 and d a capacitor 322 in parallel connected between the aforementioned positive input terminal and the reference voltage, and a negative input terminal connected on the one hand, in feedback by a 320 capacitor circuit 323 to the output terminal of the amplifier 32, and, on the other hand, to the resistor 302 of the output of the preamplifier device in non-differential mode 30.
  • each preamplifier device in non-differential mode 30 and 31 is connected to the reference voltage by means of an input resistor 300, respectively 310.
  • an adjustable resistor 313 is provided, this resistor connecting the two negative inputs of each preamplifier device in non-differential mode 30 and 31.
  • the resistor 313 may include a non-adjustable fixed resistor of non-zero value and thus allows to carry out a gain adjustment adjustment in non-differential mode of the aforementioned non-differential preamplifier devices 30 and 31.
  • a noticeable improvement of the device, object of the present invention, as shown in Figure 3, can then be made, as shown in Figure 4, in order to reduce the noise inherent in the two supply voltages 21 and 22 in the case in particular where non-symmetrical noise disturbances would appear on these supplies.
  • the electret microphone sound recording device further comprises, between the differential preamplifier stage 3 and the link by link capacity, on each input channels of the aforementioned differential preamplifier stage 3, an inverted coupling circuit of each of the input channels to the symmetrical bias circuit.
  • This inverted coupling circuit called supply rejection, makes it possible to reinject at each input terminal of the differential preamplifier stage the voltages delivered by the symmetrical inverted voltage sources, deprived of their continuous components.
  • each input of the differential amplifier stage 3 thus sees the sum of the noises of the two aforementioned supplies 21 and 22, this noise then disappearing at the output since the assembly effects the difference of the input signals.
  • the coupling circuit 4 comprises a first and a second circuit, each formed by a resistor and an electric capacitor in series, bearing the references 211, 212, respectively 221, 222.
  • the first circuit 211, 212 is connected between the second negative voltage source 21 and the first input of the differential amplifier stage 3, that is to say downstream of the connection capacity 11
  • the second circuit 221, 222 is connected between the first positive voltage source 20 and the second input of the differential preamplifier stage 3, that is to say downstream of the connection capacitor 12.
  • the power rejection circuit 4 must be identical to the bias circuit 2, the resistor 211 being identical to the resistor 210, the resistor 221 identical to the resistor 220, the capacity 212 identical at capacity 12 and capacity 222 identical to capacity 11.
  • Figure 5a the response of the assembly of the prior art shown in Figure la to a disturbance of the power supply sector, that is to say at a frequency of 50 Hz.
  • Figure 5a is graduated on the ordinate in decibels and, on the abscissa, in frequencies. The tests were carried out in the presence of a pink noise and a line at 50 Hz due to a disturbance of the sector as well as to the harmonic frequencies of the latter.
  • the response of the circuit as shown in FIG. 1 relating to the prior art, clearly exhibits parasitic noise at the frequency of the sector mentioned above.
  • the device for picking up sound by electret microphone, object of the present invention, previously described, is particularly advantageous insofar as, by the mere replacement of the transformer by a coupling circuit by capacitance link, the results, in terms of pick-up its, however, are identical to the circuits of the prior art comprising such transformers, while the cost price of implementation of these circuits have been known to be reduced.
  • circuits in accordance with the object of the present invention, is particularly advantageous in acoustic antennas or in complex circuits requiring quality sound recording.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
EP19950401674 1994-07-15 1995-07-12 Schallaufnahmevorrichtung durch Elektretmikrofon Expired - Lifetime EP0692921B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9408807 1994-07-15
FR9408807A FR2722636B1 (fr) 1994-07-15 1994-07-15 Dispositif de prise de son par microphone electret

Publications (2)

Publication Number Publication Date
EP0692921A1 true EP0692921A1 (de) 1996-01-17
EP0692921B1 EP0692921B1 (de) 2001-10-04

Family

ID=9465436

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19950401674 Expired - Lifetime EP0692921B1 (de) 1994-07-15 1995-07-12 Schallaufnahmevorrichtung durch Elektretmikrofon

Country Status (4)

Country Link
EP (1) EP0692921B1 (de)
DE (1) DE69523004T2 (de)
ES (1) ES2164140T3 (de)
FR (1) FR2722636B1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2769164A1 (fr) * 1997-09-26 1999-04-02 Alain Maurice Ange Magagnini Dispositif micro electrostatique a interface circuit integre
GB2382949A (en) * 2001-12-04 2003-06-11 Samsung Electronics Co Ltd Reducing echoes and noise caused by cross talk in a telephone handset connecting cord

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3778561A (en) * 1972-06-21 1973-12-11 Bell Canada Northern Electric Electret microphone
EP0055650A1 (de) * 1980-12-31 1982-07-07 Thomson-Csf Telephone Schaltung zur Verbindung eines aktiven Mikrophons, insbesondere mit Elektret, mit einer Fernsprechübertragungsschaltung
DE3933870A1 (de) * 1989-10-11 1991-04-18 Neumann Gmbh Georg Verfahren und schaltungsanordnung zum steuern von mikrofonen
EP0546571A1 (de) * 1991-12-12 1993-06-16 Nec Corporation Verstärkerschaltungsanordnung für ein Elektret-Kondensator Mikrofon
US5315231A (en) * 1992-11-16 1994-05-24 Hughes Aircraft Company Symmetrical bipolar bias current source with high power supply rejection ratio (PSRR)

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3778561A (en) * 1972-06-21 1973-12-11 Bell Canada Northern Electric Electret microphone
EP0055650A1 (de) * 1980-12-31 1982-07-07 Thomson-Csf Telephone Schaltung zur Verbindung eines aktiven Mikrophons, insbesondere mit Elektret, mit einer Fernsprechübertragungsschaltung
DE3933870A1 (de) * 1989-10-11 1991-04-18 Neumann Gmbh Georg Verfahren und schaltungsanordnung zum steuern von mikrofonen
EP0546571A1 (de) * 1991-12-12 1993-06-16 Nec Corporation Verstärkerschaltungsanordnung für ein Elektret-Kondensator Mikrofon
US5315231A (en) * 1992-11-16 1994-05-24 Hughes Aircraft Company Symmetrical bipolar bias current source with high power supply rejection ratio (PSRR)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2769164A1 (fr) * 1997-09-26 1999-04-02 Alain Maurice Ange Magagnini Dispositif micro electrostatique a interface circuit integre
GB2382949A (en) * 2001-12-04 2003-06-11 Samsung Electronics Co Ltd Reducing echoes and noise caused by cross talk in a telephone handset connecting cord
AU2002302014B2 (en) * 2001-12-04 2004-08-19 Samsung Electronics Co., Ltd. Apparatus for reducing echoes and noises in telephone
GB2382949B (en) * 2001-12-04 2004-09-29 Samsung Electronics Co Ltd Apparatus for reducing echoes and noises in telephone equipment
AU2002302014B9 (en) * 2001-12-04 2005-03-24 Samsung Electronics Co., Ltd. Apparatus for reducing echoes and noises in telephone
US6934383B2 (en) 2001-12-04 2005-08-23 Samsung Electronics Co., Ltd. Apparatus for reducing echoes and noises in telephone

Also Published As

Publication number Publication date
DE69523004T2 (de) 2002-06-06
FR2722636B1 (fr) 1996-09-20
FR2722636A1 (fr) 1996-01-19
DE69523004D1 (de) 2001-11-08
ES2164140T3 (es) 2002-02-16
EP0692921B1 (de) 2001-10-04

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