US3930128A - Electret diaphragm microphone with means to corrugate the diaphragm when in an overstressed condition - Google Patents

Electret diaphragm microphone with means to corrugate the diaphragm when in an overstressed condition Download PDF

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Publication number
US3930128A
US3930128A US478735A US47873574A US3930128A US 3930128 A US3930128 A US 3930128A US 478735 A US478735 A US 478735A US 47873574 A US47873574 A US 47873574A US 3930128 A US3930128 A US 3930128A
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United States
Prior art keywords
diaphragm
electrode
condenser microphone
end faces
raised portions
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Expired - Lifetime
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US478735A
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English (en)
Inventor
Werner Fidi
Herbert Piribauer
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AKG Acoustics GmbH
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AKG Akustische und Kino Geraete GmbH
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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

Definitions

  • the raised portions extend through only a art of the inters ace so that a free s ace is left er- [301 Forelgn Apphcatfon Prmnty Data iitting unimpede t i oscillation of the diaphragm in re- June 26, 1973 Austria 5624/73 spouse to normal sound Waves
  • the raised portions act as stops determining the maximum amplitude so that if [52] U.S. Cl; 179/111 R; 179/11 1 E the Sound waves are abnormally Strong the diaphragm [51] Illt. C1.
  • H04R 19/04 is deflected only up to Contact with the end faces f
  • Field of Search 179/111 R, 111 E the raised portions thus remaining Spaced from the main surface of the opposite electrode.
  • the electro- [56] References C'ted static attractive forces are thereby limited and do not UNITED STATES PATENTS prevent the diaphragm from further free oscillation. 3,328,653 6/1971 Wolf, Jr.
  • This invention relates in general to condenser microphones and, in particular, to a new and useful design of such a microphone in which the electrode responsive to sound can freely oscillate under normal conditions but is prevented from applying against the opposite electrode when exposed to abnormally strong sound waves.
  • a condenser microphone is conventionally so constructed that an electrically conductive diaphragm is disposed at a small distance from and opposite to a flat electrode having a conductive surface.
  • the electrode can be made, for instance, directly from metal or plastic having a surface which has been metallized.
  • the distance between the electrode and the diaphragm is 30-40 a, the necessary insulating layer being obtained either by a thin lacquer coating of the electrode or by using plastic sheets which are vapor treated on one side.
  • Condenser microphones are conventionally connected via a high-ohmic resistance to a voltage source, the externally applied voltage being about 60 volts.
  • the movement of the diaphragm causes direct fluctuations in voltage which are picked up by a high-ohmic amplifier.
  • Microphone constructions of this kind are expensive high precision products andthey are difficult to manufacture in mass production.
  • the disadvantage of this suggestion is that it reduces the effective diaphragm surface and also impedes the movement of the diaphragm and this results in a loss of sensitivity, more particularly in the case of microphoneswith reniform directional characteristic.
  • the electrode itself is made of an electret material with a metallized surface.
  • a condenser microphone comprising an electrode having a surface presenting raised portions and a diaphragm disposed at a small distance from the said surface of the electrode, in which microphone the raised portions of the electrode project from the surface of the electrode a distance which is less than the distance between the electrode and the diaphragm, so that an unimpeded space is provided for the oscillation of the diaphragm when sound impinges normally on the microphone.
  • the diaphragm is as a rule completely free from any support by the electrode, so that the diaphragm as a whole can follow the sound oscillations.
  • the raised portions of the electrode of a microphone embodying the invention at least impede a fairly large surface of the diaphragm from impinging on the electrode surface, if not actually preventing all contact therewith.
  • the electrostatic force occurring represents only a fraction of the force which occurs if the diaphragm bears flush against the electrode surface, the mechanical tensioning of the diaphragm is fully adequate to return it to the inoperative position when the external applied force has ceased to be operative.
  • the invention can be used in general for capacitive transducers, but is particularly advantageous for capacitive transducers which obtain the polarization voltage on the electret principle; it is immaterial whether electret diaphragms or electret electrodes are used.
  • the invention enables the polarization voltage to be increased, or the distance to be reduced if the electret effect is used, thus substantially increasing sensitivity.
  • a condenser microphone comprising two electrodes of which the first one is formed with raised por- 3 vided between the raised portions and the diaphragm permitting unimpeded oscillations of the latter.
  • Another object of the invention is to provide electrodes of which at least one comprises an electretifiable material.
  • a furtherobject of the invention is to provide the raised portions projecting from the first electrode in the form of cylindrical bodies having concave or non-conductive end faces.
  • Still another object of the invention is to provide an improved condenser microphone which is simple in design, rugged in construction and economical to manufacture.
  • FIG. 1 is a cross-sectional view of a condenser microphone embodying the invention showing the diaphragm in normal position;
  • FIG. 2 is a view similar to FIG. 1 showing the position of the diaphragm when extreme sound wave pressure conditions occur;
  • FIG. 3 is an enlarged cross-sectional view of a raised portion of the electrode, having a concave end face.
  • the invention embodied therein, comprises a condenser microphone, which is diagrammatically illustrated and is not drawn to scale.
  • the condenser microphone comprises an annular mount 2 of insulating material and two electrodes 3 and 1 affixed to mount 2 in spaced relationship.
  • Electrode l is a diaphragm, for example,
  • Electrode 3 has an annular recess 3' which defines the depth of penetration of the annular mount 2.
  • electrode 3 has a number of bores 4, so that a connection can be established between the lower air chamber behind the diaphragm and atmosphere.
  • Raised portions or projections 5, which are preferably regularly distributed, are disposed on the webs between bores 4 of electrode 3. The height of the portions 5 is less the whole distance a between the electrode and the diaphragm. Portions 5 terminate at a free distance c from the underside of the diaphragm.
  • the raised portions 5 are to be too numerous, their height above the electrode is conveniently about 36 a. There is then left for the diaphragm a free space of height 4: a, in which it can oscillate without impediment. In practice, the distance a is about 40 pm.
  • diaphragm 1 When diaphragm l is overstressed, it is forced against electrode 3. As a result of the raised portions 5, disposed on the electrode 3, diaphragm 1 is prevented from bearing flush against electrode 3. Diaphragm 1, therefore, occupies a position 1', as shown approximately in section in FIG. 2. The raised portions act as 4 a support for diaphragm 1', and prevent it from-contacting those areas of electrode 3 which have no raised portions 5.
  • the electrostatic force of attraction increases in direct proportion to the contact surface and decreases quadratically with the distance between the opposite surfaces, it can be seen that with a condenser microphone embodying the invention, if the diaphragm is overstressed, the effect of electrostatic attraction represents only a fraction of that which would be exerted if the diaphragm 1 were to bear flush against electrode 3.
  • the mechanical tensionin g of the diaphragm l is adequate to return it to its normal position after the overstressing has ceased.
  • Raised portions 5 can take the form of small cylinders having a flat end face adjacent the diaphragm. However, it has been found to be particularly advantageous, if the applied forces are so great as to cause the diaphragm to bear against the electrode, to make the end face 5' of the raised portion concave, as shown in section in FIG. 3. As a result, the mechanical tensioning of the diaphragm and therefore its return force are substantially enhanced.
  • a condenser microphone embodying the invention has either high sensitivity or, for at least equal sensitivity, a substantially improved reproducibility, accompanied by increased resistance to overloadings of all kinds.
  • a condenser microphone comprising an electrode having a surface, an electret diaphragm at a spaced location from said surface, and means for corrugating said diaphragm in the event said diaphragm becomes overstressed, comprising at least one pin-like projection extending outwardly from said surface in normally spaced relation to said electrode," the space between said pin-like projection and said diaphragm being unimpeded to permit oscillation of said diaphragm in response to normal sound waves.
  • a condenser microphone comprising a mount, a first electrode connected to said mount and having an upper surface, and a second electrode in the form of an electretifiable foil diaphragm connected to said mount and having a lower surface facing said upper surface of said electrode and spaced therefrom by a small distance, and means for corrugating said diaphragm in the event said diaphragm becomes overstressed, comprising a plurality of pin-like raised projections projecting from and distributed over said upper surface of said first electrode and having end faces turned to said lower surface of said diaphragm and spaced therefrom by a free distance so that a free space adjacent said diaphragm is providedbetween said end faces and said diaphragm permitting unimpeded oscillations of the latter in response to normal sound waves.
  • a condenser microphone according to claim 2,

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
US478735A 1973-06-26 1974-06-12 Electret diaphragm microphone with means to corrugate the diaphragm when in an overstressed condition Expired - Lifetime US3930128A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AT562473A AT323257B (de) 1973-06-26 1973-06-26 Kondensatormikrophon

Publications (1)

Publication Number Publication Date
US3930128A true US3930128A (en) 1975-12-30

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ID=3577829

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US478735A Expired - Lifetime US3930128A (en) 1973-06-26 1974-06-12 Electret diaphragm microphone with means to corrugate the diaphragm when in an overstressed condition

Country Status (5)

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US (1) US3930128A (de)
JP (1) JPS5038518A (de)
AT (1) AT323257B (de)
DE (1) DE2430068C2 (de)
GB (1) GB1445504A (de)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4311881A (en) * 1979-07-05 1982-01-19 Polaroid Corporation Electrostatic transducer backplate having open ended grooves
US4429192A (en) 1981-11-20 1984-01-31 Bell Telephone Laboratories, Incorporated Electret transducer with variable electret foil thickness
US4434327A (en) 1981-11-20 1984-02-28 Bell Telephone Laboratories, Incorporated Electret transducer with variable actual air gap
US4495385A (en) * 1982-12-02 1985-01-22 Honeywell Inc. Acoustic microphone
US4610062A (en) * 1982-12-02 1986-09-09 Honeywell Inc. Method of making an acoustic microphone
WO2000035246A1 (en) * 1998-12-07 2000-06-15 American Technology Corporation Electrostatic transducer with nonplanar configured diaphragm
US6510231B2 (en) * 2000-01-27 2003-01-21 Akg Acoustics Gmbh Electroacoustic transducer
WO2006095946A1 (en) * 2005-03-10 2006-09-14 Bse Co., Ltd. Improved condenser microphone
US20070235407A1 (en) * 2006-04-10 2007-10-11 Hsien-Lung Ho Method of fabricating a diaphragm of a capacitive microphone device
US20100092013A1 (en) * 2008-10-15 2010-04-15 Fang-Ching Lee Electro-acoustic transducer
TWI448162B (zh) * 2008-10-15 2014-08-01 Htc Corp 電聲換能器

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT385386B (de) * 1986-07-24 1988-03-25 Akg Akustische Kino Geraete Elektrostatischer wandler

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3328653A (en) * 1966-09-22 1967-06-27 Budd Co Thin film pressure transducer
US3418436A (en) * 1964-07-21 1968-12-24 Neumann Georg Unidirectional condenser microphone

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1639444B2 (de) * 1967-05-15 1972-08-03 Thermo Electron Engineering Corp., Waltham, Mass. (V.StA.) Elektroakustischer wandler

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3418436A (en) * 1964-07-21 1968-12-24 Neumann Georg Unidirectional condenser microphone
US3328653A (en) * 1966-09-22 1967-06-27 Budd Co Thin film pressure transducer

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4311881A (en) * 1979-07-05 1982-01-19 Polaroid Corporation Electrostatic transducer backplate having open ended grooves
US4429192A (en) 1981-11-20 1984-01-31 Bell Telephone Laboratories, Incorporated Electret transducer with variable electret foil thickness
US4434327A (en) 1981-11-20 1984-02-28 Bell Telephone Laboratories, Incorporated Electret transducer with variable actual air gap
US4495385A (en) * 1982-12-02 1985-01-22 Honeywell Inc. Acoustic microphone
US4610062A (en) * 1982-12-02 1986-09-09 Honeywell Inc. Method of making an acoustic microphone
WO2000035246A1 (en) * 1998-12-07 2000-06-15 American Technology Corporation Electrostatic transducer with nonplanar configured diaphragm
US6510231B2 (en) * 2000-01-27 2003-01-21 Akg Acoustics Gmbh Electroacoustic transducer
EP1120996A3 (de) * 2000-01-27 2008-05-14 AKG Acoustics GmbH Elektroakustischer Wandler
WO2006095946A1 (en) * 2005-03-10 2006-09-14 Bse Co., Ltd. Improved condenser microphone
US20070235407A1 (en) * 2006-04-10 2007-10-11 Hsien-Lung Ho Method of fabricating a diaphragm of a capacitive microphone device
US7585417B2 (en) * 2006-04-10 2009-09-08 Touch Micro-System Technology Inc. Method of fabricating a diaphragm of a capacitive microphone device
US20100092013A1 (en) * 2008-10-15 2010-04-15 Fang-Ching Lee Electro-acoustic transducer
US8472650B2 (en) * 2008-10-15 2013-06-25 Htc Corporation Electro-acoustic transducer
TWI448162B (zh) * 2008-10-15 2014-08-01 Htc Corp 電聲換能器

Also Published As

Publication number Publication date
AT323257B (de) 1975-07-10
DE2430068A1 (de) 1975-01-16
JPS5038518A (de) 1975-04-10
DE2430068C2 (de) 1983-05-05
GB1445504A (en) 1976-08-11

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