US3418436A - Unidirectional condenser microphone - Google Patents

Unidirectional condenser microphone Download PDF

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Publication number
US3418436A
US3418436A US472419A US47241965A US3418436A US 3418436 A US3418436 A US 3418436A US 472419 A US472419 A US 472419A US 47241965 A US47241965 A US 47241965A US 3418436 A US3418436 A US 3418436A
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United States
Prior art keywords
diaphragm
back plate
microphone
grooves
condenser microphone
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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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US472419A
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English (en)
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Neumann Georg
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Individual
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Individual
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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
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • 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
    • H04R1/20—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
    • H04R1/38—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 in which sound waves act upon both sides of a diaphragm and incorporating acoustic phase-shifting means, e.g. pressure-gradient microphone
    • 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
    • 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

Definitions

  • ABSTRACT OF THE DISCLOSURE A unidirectional condenser microphone which improves the polar diagram in the frequency region between approximately 6 and approximately 12 kc.p.s., comprising a back plate of the microphone formed with holes extending from the surface of the plate in front of the diaphragm into an acoustical impedance and from this impedance to an opening at the rear of the microphone, and the back plate formed with grooved distributed on its surface in front of the diaphragm, the holes terminating in the grooves, preferably in the crossing points of the grooves.
  • the present invention relates to a unidirectional condenser microphone and is concerned with the construction of the back plate of a condenser microphone consisting preferably of a diaphragm and of a back plate, which are the two electrodes being insulated from each other.
  • the back plate arranged behind the diaphragm consists of a plane metallic or metallized plate which has many holes.
  • the compliance of the air volume between the diaphragm and the back plate would be too small.
  • at least some of the holes must be deep enough to reach one or more openings of the microphone case, the openings being arranged at some distance behind the area of the diaphragm, to insure that also the rear of the diaphragm may be reached by the sound waves.
  • an air-filled chamber in the form of a short cylinder is arranged inside or straight behind the back plate of capacitive unidirectional microphones. That air-filled chamber fulfills the following tasks:
  • FIGURE 1 is a cross-section of a known capacitive pressure-gradient microphone with a time delay device disposed behind the diaphragm;
  • FIG. 2 is a rear elevation thereof
  • FIG. 3 is a cross-section of the condenser microphone, designed in accordance with the present invention, shown at an enlarged scale;
  • FIG. 4 is a front elevation of the microphone disclosed in FIG. 3;
  • FIG. 5 is a cross-section of the condenser microphone capsule, disclosing a variation of the friction element.
  • the known condenser microphone in FIGS. 1 and 2 comprises a housing 1 to which the diaphragm 1 is secured and which receives a back plate 3. Inside the back plate 3 is an air-filled chamber 5. A plurality of drilled holes 4 extend from the outer surface of the back plate 3 into the chamber 5 and a small number of drilled holes 6 or, instead of that, a number of slits or other air-ducts together with an appropriate acoustical impedance 7 connect the air-filled chamber 5 with an opening 8 at the rear or at the periphery of the microphone.
  • the polar diagram of all known unidirectional microphones in the frequency region between approximately 6 and approximately 12 kc.p.s. has discontinuities and irregularities, due to the volume of the airfilled chamber.
  • the microphone-polar-diagram again becomes better by the influence of the sound diffraction on the diaphragm not yet being small compared with the sound-wavelength and by the influence of soundshadowing-effects.
  • the back plate of the present microphone is equipped with grooves disposed on its surface and with drilled holes ending in these grooves.
  • the local arrangement, the number and the cross-section area of the grooves may be varied over a wide range.
  • the grooves may be straight or curved. They may cross one another; but crossing is not necessary. When crossing one another, the small number of drilled holes may end in the crossing points of the grooves effecting thereby a good distribution of the sound. It is very useful, when the grooves form a line-net spreading all over the upper area of the back plate behind the diaphragm.
  • the single parts of the sound energy conducted to the rear of the diaphragm will reach the diaphragm by some separated ways without being joined indefinitely with one another.
  • the single components of the sound energy are joined when reaching the zone directly behind the diaphragm. That means, they are joined in a region where in any case it is necessary to combine the difierent forces.
  • FIGS. 3 and 4 an example of a principal arrangement of the microphone according to the present invention, is illustrated, comprising a back plate 3 which has grooves 9 crossing one another. Behind the diaphragm 1' an air slit 2' is provided. The back has six grooves 9 crossing each other. In the crossing points of the grooves 9, drilled holes 10 terminate.
  • the acoustical resistance 11 belonging to the phase shifting network of the microphone may be built of textures or wickerwork consisting of textiles, synthetic plastics or wires, or of a porous sintered material.
  • the components of the microphone are mounted in a housing 14 by means of a shell 12 and a clamping ring 13, both elements consisting of non-conductive material.
  • FIG. 4 the diaphragm 1 is not shown, to make visible the back plate 3 with the grooves 9 and the drilled holes 10.
  • the mentioned acoustical resistance consists of a friction element formed by an air space as slit 17.
  • An acoustical resistance formed in this manner may be built in a simple way. It is easily adjustable and of good stability, when adjusted.
  • a perforated plate 15 is provided and has, for instance, twelve drilled holes 16 and is mounted at a very small distance spaced behind the back plate 3. Its drilled holes 16 are not aligned with the drilled holes 10 of the back plate 3 but are laterally displaced a small distance.
  • the width of the slits 17 controls its acoustical resistance and may be adjusted by appropriate profiling of the back plate or of the perforated plates as well as by an intermediate layer, for instance in the form of a circleor ring-shaped foil 18.
  • FIG. 5 The other parts shown in FIG. 5 are identical with those disclosed in FIGS. 3 and 4 and bear the same numerals.
  • Unidirectional microphones constructed in accordance with the present invention in the critical frequency range between six and twelve kilocycles/sec. have the same good front-to-back-ratio as known unidirectional microphones only have in the frequency section below 6 kc.p.s. and above 12 kc.p.s. Moreover, the frequency response of the described microphones in the whole frequency range and for all angles of sound incidence, wherein the microphone receives at least some remarkable sound energy, is of excellent linearity.
  • a microphone built in accordance with the present invention may be manufactured by simpler methods than all unidirectional condenser microphones heretofore and its acoustical transducer features are of better reproducibility than for all unidirectional condenser microphones manufactured until now.
  • a unidirectional condenser microphone comprising an electrically conductive diaphragm
  • said back plate having holes extending from the surface of said back plate in front of said diaphragm into said acoustical impedance means and from this impedance to said opening at the rear of said microphone,
  • said back plate having surface grooves distributed over its surface in front of said diaphragm
  • the condenser microphone as set forth in claim 1, which includes a perforated plate disposed behind said back plate and having a plurality of additional holes,
  • said additional holes being laterally displaced relative to said holes of said back plate.
  • the condenser microphone as set forth in claim 3, which includes a substantially ring-shaped foil disposed between said back plate and said perforated plate, in order to control the distance between said plates.
  • said acoustical impedance means includes at least one acoustical resistance member disposed adjacent the back side of said back plate.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
US472419A 1964-07-21 1965-07-16 Unidirectional condenser microphone Expired - Lifetime US3418436A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE1437420A DE1437420C3 (de) 1964-07-21 1964-07-21 Kondensator-Richtmikrophonkapsel

Publications (1)

Publication Number Publication Date
US3418436A true US3418436A (en) 1968-12-24

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Application Number Title Priority Date Filing Date
US472419A Expired - Lifetime US3418436A (en) 1964-07-21 1965-07-16 Unidirectional condenser microphone

Country Status (4)

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US (1) US3418436A (de)
AT (1) AT264614B (de)
DE (1) DE1437420C3 (de)
SE (1) SE331297B (de)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2337078A1 (de) * 1972-07-21 1974-02-07 Ind Res Products Inc Richtungsempfindliche hoerhilfe
US3930128A (en) * 1973-06-26 1975-12-30 Akg Akustische Kino Geraete Electret diaphragm microphone with means to corrugate the diaphragm when in an overstressed condition
FR2461422A1 (fr) * 1979-07-05 1981-01-30 Polaroid Corp Plaque arriere de transducteur electrostatique possedant des rainures ouvertes a leurs extremites
US4582961A (en) * 1981-11-13 1986-04-15 Aktieselskabet Bruel & Kjar Capacitive transducer
US4704556A (en) * 1983-12-05 1987-11-03 Leslie Kay Transducers
WO2007031270A1 (de) * 2005-09-14 2007-03-22 Sennheiser Electronic Gmbh & Co. Kg Kapazitiver schallwandler mit perforierter dämpfungsscheibe
US20080165993A1 (en) * 2007-01-05 2008-07-10 Samsung Electronics Co., Ltd. Directional speaker system and automatic set-up method thereof
US20090146527A1 (en) * 2007-12-07 2009-06-11 Electronics And Telecommunications Research Institute Piezoelectric microspeaker using microelectromechanical systems and method of manufacturing the same
US20140216161A1 (en) * 2011-06-24 2014-08-07 Avl List Gmbh Capacitive ultrasonic transducer
US9573695B2 (en) 2013-02-22 2017-02-21 United Technologies Corporation Integrated nozzle and plug

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2119912C3 (de) * 1971-04-23 1974-12-12 Siemens Ag, 1000 Berlin Und 8000 Muenchen Elektroakustischer Wandler
JPS622879Y2 (de) * 1981-03-25 1987-01-22

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1456538A (en) * 1923-05-29 Acoustic apparatus
US2910539A (en) * 1956-07-27 1959-10-27 William L Hartsfield Microphones
US3118979A (en) * 1961-08-07 1964-01-21 Bell Telephone Labor Inc Electrostatic transducer
US3190972A (en) * 1961-07-08 1965-06-22 Schall Technik Condenser microphone

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1456538A (en) * 1923-05-29 Acoustic apparatus
US2910539A (en) * 1956-07-27 1959-10-27 William L Hartsfield Microphones
US3190972A (en) * 1961-07-08 1965-06-22 Schall Technik Condenser microphone
US3118979A (en) * 1961-08-07 1964-01-21 Bell Telephone Labor Inc Electrostatic transducer

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2337078A1 (de) * 1972-07-21 1974-02-07 Ind Res Products Inc Richtungsempfindliche hoerhilfe
US3930128A (en) * 1973-06-26 1975-12-30 Akg Akustische Kino Geraete Electret diaphragm microphone with means to corrugate the diaphragm when in an overstressed condition
FR2461422A1 (fr) * 1979-07-05 1981-01-30 Polaroid Corp Plaque arriere de transducteur electrostatique possedant des rainures ouvertes a leurs extremites
US4582961A (en) * 1981-11-13 1986-04-15 Aktieselskabet Bruel & Kjar Capacitive transducer
US4704556A (en) * 1983-12-05 1987-11-03 Leslie Kay Transducers
US20100061572A1 (en) * 2005-09-14 2010-03-11 Manfred Hibbing Capacitve Sound Transducer Having a Perforated Attenuation Disk
WO2007031270A1 (de) * 2005-09-14 2007-03-22 Sennheiser Electronic Gmbh & Co. Kg Kapazitiver schallwandler mit perforierter dämpfungsscheibe
US8126168B2 (en) 2005-09-14 2012-02-28 Sennheiser Electronic Gmbh & Co. Kg Capacitive sound transducer having a perforated attenuation disk
US20080165993A1 (en) * 2007-01-05 2008-07-10 Samsung Electronics Co., Ltd. Directional speaker system and automatic set-up method thereof
US8325952B2 (en) * 2007-01-05 2012-12-04 Samsung Electronics Co., Ltd. Directional speaker system and automatic set-up method thereof
US7812505B2 (en) * 2007-12-07 2010-10-12 Electronics And Telecommunications Research Institute Piezoelectric microspeaker using microelectromechanical systems and method of manufacturing the same
US20090146527A1 (en) * 2007-12-07 2009-06-11 Electronics And Telecommunications Research Institute Piezoelectric microspeaker using microelectromechanical systems and method of manufacturing the same
US20140216161A1 (en) * 2011-06-24 2014-08-07 Avl List Gmbh Capacitive ultrasonic transducer
US9816854B2 (en) * 2011-06-24 2017-11-14 Avl List Gmbh Capacitive ultrasonic transducer
US9573695B2 (en) 2013-02-22 2017-02-21 United Technologies Corporation Integrated nozzle and plug

Also Published As

Publication number Publication date
DE1437420A1 (de) 1968-10-17
AT264614B (de) 1968-09-10
SE331297B (de) 1970-12-21
DE1437420C3 (de) 1978-06-22
DE1437420B2 (de) 1972-11-30

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