US2778882A - Microphones - Google Patents

Microphones Download PDF

Info

Publication number
US2778882A
US2778882A US254567A US25456751A US2778882A US 2778882 A US2778882 A US 2778882A US 254567 A US254567 A US 254567A US 25456751 A US25456751 A US 25456751A US 2778882 A US2778882 A US 2778882A
Authority
US
United States
Prior art keywords
diaphragm
coil
microphone
housing
magnet
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.)
Expired - Lifetime
Application number
US254567A
Inventor
Pontzen George Raoul
Clark Robert Richard
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.)
LUSTRAPHONE Ltd
Original Assignee
LUSTRAPHONE Ltd
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 LUSTRAPHONE Ltd filed Critical LUSTRAPHONE Ltd
Application granted granted Critical
Publication of US2778882A publication Critical patent/US2778882A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • 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

Definitions

  • One of the objects of the present invention is to provide a microphone which is largely, if not wholly, non-responsive to background noises, that is to say, noises emanating from a relatively distant source, but which is suitable for transmitting sounds applied to the microphone from a close source.
  • Microphones fullling this object can be advantageously employed in aircraft, in vehicles with a high ambient noise level, in crowded surroundings and under noisy conditions in general.
  • a microphone comprising a plane diaphragm, both faces of the diaphragm being substantially freely accessible to the surrounding air over substantially the whole peripheral extent of the diaphragm, means for supporting the diaphragm so that the latter can vibrate, a coil supported from the diaphragm to move in correspondence with the vibration of the diaphragm, and means for establishing a magnetic iield whereby movement of the coil in the ield causes an electromotive force to be induced in the wires of the coil, the arrangement being such that sound waves from a relatively distant source cause substantially no vibration of the diaphragm and sound waves from a relatively close source not in the plane of the diaphragm cause vibration of the diaphragm.
  • the housing and openings constitute means for directing sound waves initiated at a distance to impress these waves upon the two opposite faces of the diaphragm in substantially identical phase and amplitude.
  • the diaphragm being substantially freely accessible to the surrounding air over substantially the whole peripheral extent of the diaphragm.
  • Figure 1 is a cross-sectional elevation of a microphone having a centrally supported diaphragm
  • Figure 2 is a plan view of the magnet housing of the microphone shown in Figure 1, and
  • Figure 3 is a cross-sectional elevation of a microphone having a peripherally supported diaphragm.
  • the microphone shown in Figure 1 has a pot-type magnet comprising a permanent magnet 1 having a centrally disposed pole-piece 2 secured thereon.
  • a magnet housing 3 of hollow cylindrical form closed at the lower end by a base plate 3A encloses the magnet 1 and pole-piece 2.
  • the pole-piece 2 is disposed within a circular opening in the top of the housing 3, whereby an annular air gap 4 is formed between the pole-piece 2 and the housing 3.
  • the iron circuit of the magnet consists of pole-piece 2, magnet 1, base plate 3A and housing 3, the polepiece 2 being of opposite polarity to that portion of the housing adjacent the pole-piece.
  • the diaphragm 7 is secured on the pole-piece 2 by means of an upstanding stud 8 which is passed through the centre of the diaphragm 7 and has a nut 9 threaded thereon,
  • a thick washer 10 is interposed between the diaphragm 7 and the pole-piece 2, and a washer 11 is interposed between the nut 9 and diaphragm 7.
  • a plurality of recesses 12 are formed around the upper outer periphery of the housing 3 to ensure that the underside face of the peripheral edge portion of the diaphragm is freely in contact with the surrounding air.
  • the 'recessed top of the housing 3 has a castellated appearance.
  • the diaphragm is protected against damage by a perforated cover 13, the bottom of which is secured to the side wall of the housing 3. lt is to be understood that the cover 13 allows sound waves to be transmitted freely therethrough and in no way serves as a guide for directing sound waves onto the two opposite faces of the diaphragm 7.
  • a washer 15 is provided within the housing 3 for closing the cavity between the housing 3 and the magnet 1.
  • the diaphragm 7 has a plurality of holes 16A therethrough, the holes being disposed in a ring around the washer LD.
  • the microphone shown in Figure 3 is similar to Figure l except that the central support for the diaphragm is omitted and instead the diaphragm is supported at its periphery.
  • a plurality of pillars 14 screwed into the housing 3 support a mounting ring 17.
  • a diaphragm 16 is secured between the ring 17 and a clamping ring 1S which latter is secured to the pillars 14.
  • the diaphragm 16 has an aperture 19 at the centre thereof.
  • the housing 3 shown in Figure 3 tapers towards the diaphragm 16 so that the underside face of the diaphragm 16 has free access to the surrounding air.
  • the microphones described above with reference to the gures operate as follows. Sounds originating from a relatively distant source cause pressure waves to impinge simultaneously and substantially equally on the upper and under-sides of the diaphragm. The forces acting on the upper and under-sides of the diaphragm are, therefore, substantially balanced and substantially no vibration ot the diaphragm takes place. Hence substantially no electrornotive force is generated in the coil 5.
  • a relatively close point source for example, a persons mouth
  • the pressure waves impinge upon the upper side of the diaphragm with greater intensity than they do on the under-side of the diaphragm.
  • the coil S moves with the diaphragm 7 or 16 as the case may be, and cuts magnetic lines of force across the air gap 4, whereby an electromotive force is induced in the coil.
  • a microphone comprising an effectively plane diaphragm, supporting means for the diaphragm permitting vibration of the latter, said means engaging the diaphragm over an area which leaves substantially the Whole of the peripheral extent of the diaphragm substantially freely accessible to the atmosphere surrounding the microphone whereby both faces of the diaphragm become substantially freely accessible to the atmosphere surrounding the microphone, a coil supported from the diaphragm to move in correspondence with the vibration of the dia phragm, means for establishing a magnetic eld whereby movement of the coil in the eld causes an electromotive force to be induced in the wires of the coil, and the diaphragm having at least one aperture within the area covered by the coil, the arrangement thus being such that sound waves from a relatively distant source cause substantially no vibration of the diaphragm and sound waves from a relatively close source not in the plane of the diaphragm cause vibration of the diaphragm.
  • a microphone comprising an effectively plane diaphragm, both faces of the diaphragm being substantially freely accessible to the air surrounding the microphone over substantially the whole peripheral extent of the diaphragm, a coil of annular form supported from the diaphragm to move in correspondence with the vibration of the diaphragm, a pot-type permanent magnet having an annular air gap in which the coil is located, whereby movement of the coil causes an electromotive force to be induced in the wires of the coil, a support rigidly securing the central portion of the diaphragm to the central pole of the pot-type magnet, and the diaphragm having a plurality of holes arranged in a ring around said support.
  • a microphone comprising an eectively plane diaphragm, both faces of the diaphragm being substantially freely accessible to the air surrounding the microphone over substantially the Whole peripheral extent of the diaphragm, a coil of annular form supported from the diaphragm to move in correspondence with the vibration of the diaphragm, a pot-type permanent magnet of cylindrical form and having an annular air gap in which the coil is located, whereby movement of the coil causes an electromotive force to be induced in the wires of the coil, a support rigidly securing the central portion of the diaphragm to the central pole of the pot-type magnet, and there being recesses at the outer periphery of the magnet adjacent the diaphragm to provide free access of the surrounding air to the face of the diaphragm adjacent the magnet.

Landscapes

  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)

Description

Jan. 22, 1957 G. R. PoNTzx-:N ETAL 2,778,882
MICROPHONES Filed Nov. 2, 1951 /VEN for( ef/vr United States Patent MICROPHONES Application November 2, 1951, Serial No. 254,567
Claims priority, application Great Britain January 11, 1951 3 Claims. (Cl. 179-1155) This invention relates to microphones.
One of the objects of the present invention is to provide a microphone which is largely, if not wholly, non-responsive to background noises, that is to say, noises emanating from a relatively distant source, but which is suitable for transmitting sounds applied to the microphone from a close source.
Microphones fullling this object can be advantageously employed in aircraft, in vehicles with a high ambient noise level, in crowded surroundings and under noisy conditions in general.
According to the present invention there is provided a microphone comprising a plane diaphragm, both faces of the diaphragm being substantially freely accessible to the surrounding air over substantially the whole peripheral extent of the diaphragm, means for supporting the diaphragm so that the latter can vibrate, a coil supported from the diaphragm to move in correspondence with the vibration of the diaphragm, and means for establishing a magnetic iield whereby movement of the coil in the ield causes an electromotive force to be induced in the wires of the coil, the arrangement being such that sound waves from a relatively distant source cause substantially no vibration of the diaphragm and sound waves from a relatively close source not in the plane of the diaphragm cause vibration of the diaphragm.
We are aware that it has been previously proposed in United States Patent No. 2,350,010 to provide a microphone having a peripherally supported diaphragm mounted within a housing such that the diaphragm divides the housing into two compartments, there being two openings in the housing, one leading into each compartment so that if vibrations or sound waves are applied equally at the 50 housing openings, the waves will act equally upon the diaphragm to prevent vibration thereof. When, however, sound waves are emitted in close spaced relation to, and are directed into, one ofthe openings of the previously proposed microphone, the diaphragm vibrates, whereby a 5r coil is moved correspondingly in a magnetic eld and an electromotive force is generated in the wires of the coil.
in the previously proposed microphone, the housing and openings constitute means for directing sound waves initiated at a distance to impress these waves upon the two opposite faces of the diaphragm in substantially identical phase and amplitude. In the microphone according to the present invention there is no such means for directing the sound waves, the diaphragm being substantially freely accessible to the surrounding air over substantially the whole peripheral extent of the diaphragm.
For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made to the accompanying drawings, in which:
Figure 1 is a cross-sectional elevation of a microphone having a centrally supported diaphragm;
rice
Figure 2 is a plan view of the magnet housing of the microphone shown in Figure 1, and
Figure 3 is a cross-sectional elevation of a microphone having a peripherally supported diaphragm.
The microphone shown in Figure 1 has a pot-type magnet comprising a permanent magnet 1 having a centrally disposed pole-piece 2 secured thereon. A magnet housing 3 of hollow cylindrical form closed at the lower end by a base plate 3A encloses the magnet 1 and pole-piece 2. The pole-piece 2 is disposed within a circular opening in the top of the housing 3, whereby an annular air gap 4 is formed between the pole-piece 2 and the housing 3. The iron circuit of the magnet consists of pole-piece 2, magnet 1, base plate 3A and housing 3, the polepiece 2 being of opposite polarity to that portion of the housing adjacent the pole-piece.
A coil 5 disposed in the air gap 4, is wound on a former 6, which latter is supported from a diaphragm 7. The diaphragm 7 is secured on the pole-piece 2 by means of an upstanding stud 8 which is passed through the centre of the diaphragm 7 and has a nut 9 threaded thereon, A thick washer 10 is interposed between the diaphragm 7 and the pole-piece 2, and a washer 11 is interposed between the nut 9 and diaphragm 7.
A plurality of recesses 12 (Figure 2) are formed around the upper outer periphery of the housing 3 to ensure that the underside face of the peripheral edge portion of the diaphragm is freely in contact with the surrounding air. The 'recessed top of the housing 3 has a castellated appearance.
The diaphragm is protected against damage by a perforated cover 13, the bottom of which is secured to the side wall of the housing 3. lt is to be understood that the cover 13 allows sound waves to be transmitted freely therethrough and in no way serves as a guide for directing sound waves onto the two opposite faces of the diaphragm 7.
A washer 15 is provided within the housing 3 for closing the cavity between the housing 3 and the magnet 1.
The diaphragm 7 has a plurality of holes 16A therethrough, the holes being disposed in a ring around the washer LD.
The microphone shown in Figure 3 is similar to Figure l except that the central support for the diaphragm is omitted and instead the diaphragm is supported at its periphery. For this purpose, a plurality of pillars 14 screwed into the housing 3 support a mounting ring 17. A diaphragm 16 is secured between the ring 17 and a clamping ring 1S which latter is secured to the pillars 14. The diaphragm 16 has an aperture 19 at the centre thereof.
The housing 3 shown in Figure 3 tapers towards the diaphragm 16 so that the underside face of the diaphragm 16 has free access to the surrounding air.
The microphones described above with reference to the gures, operate as follows. Sounds originating from a relatively distant source cause pressure waves to impinge simultaneously and substantially equally on the upper and under-sides of the diaphragm. The forces acting on the upper and under-sides of the diaphragm are, therefore, substantially balanced and substantially no vibration ot the diaphragm takes place. Hence substantially no electrornotive force is generated in the coil 5. When sound waves emanate from a relatively close point source (for example, a persons mouth) above the microphone as seen in Figure l or 3, the pressure waves impinge upon the upper side of the diaphragm with greater intensity than they do on the under-side of the diaphragm. Hence the forces acting on the diaphragm are unequal and the latter vibrates. The coil S moves with the diaphragm 7 or 16 as the case may be, and cuts magnetic lines of force across the air gap 4, whereby an electromotive force is induced in the coil.
We claim:
1. A microphone comprising an effectively plane diaphragm, supporting means for the diaphragm permitting vibration of the latter, said means engaging the diaphragm over an area which leaves substantially the Whole of the peripheral extent of the diaphragm substantially freely accessible to the atmosphere surrounding the microphone whereby both faces of the diaphragm become substantially freely accessible to the atmosphere surrounding the microphone, a coil supported from the diaphragm to move in correspondence with the vibration of the dia phragm, means for establishing a magnetic eld whereby movement of the coil in the eld causes an electromotive force to be induced in the wires of the coil, and the diaphragm having at least one aperture within the area covered by the coil, the arrangement thus being such that sound waves from a relatively distant source cause substantially no vibration of the diaphragm and sound waves from a relatively close source not in the plane of the diaphragm cause vibration of the diaphragm.
2. A microphone comprising an effectively plane diaphragm, both faces of the diaphragm being substantially freely accessible to the air surrounding the microphone over substantially the whole peripheral extent of the diaphragm, a coil of annular form supported from the diaphragm to move in correspondence with the vibration of the diaphragm, a pot-type permanent magnet having an annular air gap in which the coil is located, whereby movement of the coil causes an electromotive force to be induced in the wires of the coil, a support rigidly securing the central portion of the diaphragm to the central pole of the pot-type magnet, and the diaphragm having a plurality of holes arranged in a ring around said support.
3. A microphone comprising an eectively plane diaphragm, both faces of the diaphragm being substantially freely accessible to the air surrounding the microphone over substantially the Whole peripheral extent of the diaphragm, a coil of annular form supported from the diaphragm to move in correspondence with the vibration of the diaphragm, a pot-type permanent magnet of cylindrical form and having an annular air gap in which the coil is located, whereby movement of the coil causes an electromotive force to be induced in the wires of the coil, a support rigidly securing the central portion of the diaphragm to the central pole of the pot-type magnet, and there being recesses at the outer periphery of the magnet adjacent the diaphragm to provide free access of the surrounding air to the face of the diaphragm adjacent the magnet.
rReferences Cited in the le of this patent UNITED STATES PATENTS 2,002,189 Round et al. May 21, 1935 2,238,741 Lauer Apr. 15, 1941 2,293,078 Proctor Aug. 18, 1942 2,534,157 Zuerker Dec. 12, 1950 2,537,253 Andersen Ian. 9, 1951 2,549,963 De Boer Apr. 24, 1951 FOREIGN PATENTS 556,412 France Apr. 12, 1923 505,407 Germany Aug. 20, 1930 599,424 Germany July 2, 1934 679,439 Germany Aug. 5, 1939 936,121 France July 9, 1948
US254567A 1951-01-11 1951-11-02 Microphones Expired - Lifetime US2778882A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB846/51A GB698695A (en) 1951-01-11 1951-01-11 Improvements in or relating to microphones

Publications (1)

Publication Number Publication Date
US2778882A true US2778882A (en) 1957-01-22

Family

ID=9711475

Family Applications (1)

Application Number Title Priority Date Filing Date
US254567A Expired - Lifetime US2778882A (en) 1951-01-11 1951-11-02 Microphones

Country Status (2)

Country Link
US (1) US2778882A (en)
GB (1) GB698695A (en)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3149254A (en) * 1961-08-07 1964-09-15 Thomas A Carter Linear motor or generator
DE1201876B (en) * 1963-04-11 1965-09-30 Alexander Wiesbauer Centering and holding device for loudspeaker membranes, in particular flat membranes
US3246721A (en) * 1962-04-27 1966-04-19 Siemens Ag Frequency response of an electroacoustic transducer
DE1223421B (en) * 1962-07-31 1966-08-25 Dr Wolfgang Felix Ewald speaker
US4757548A (en) * 1985-12-02 1988-07-12 Fenner Jr Thomas C Speaker system and dome-shaped enclosure therefor
US4843628A (en) * 1986-07-10 1989-06-27 Stanton Magnetics, Inc. Inertial microphone/receiver with extended frequency response
US5473700A (en) * 1993-11-24 1995-12-05 Fenner, Jr.; Thomas C. High gain acoustic transducer
US20150163572A1 (en) * 2013-12-05 2015-06-11 Apple Inc. Pressure Vent for Speaker or Microphone Modules

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR556412A (en) * 1923-05-09 1923-07-20 Const Electr De Lyon Et Du Dau Improvements to speaker phones
DE505407C (en) * 1924-12-13 1930-08-20 Aeg Apparatus for converting electrical energy into sound energy and vice versa
DE599424C (en) * 1930-02-28 1934-07-02 Telefunken Gmbh Electrodynamic telephone or microphone
US2002189A (en) * 1927-04-22 1935-05-21 Rca Corp Acoustic device
DE679439C (en) * 1935-04-10 1939-08-05 Pertrix Chem Fab Akt Ges Cone loudspeaker with electrodynamic drive system
US2238741A (en) * 1938-02-22 1941-04-15 Gen Electric Electrodynamic transducer
US2293078A (en) * 1939-12-05 1942-08-18 B A Proctor Company Inc Microphone
FR936121A (en) * 1946-11-15 1948-07-09 Loudspeaker enhancements
US2534157A (en) * 1949-06-04 1950-12-12 Gen Electric Sound reproducing device
US2537253A (en) * 1946-08-20 1951-01-09 Chris S Andersen Electrodynamic telephone receiver
US2549963A (en) * 1945-12-03 1951-04-24 Hartford Nat Bank & Trust Co Electroacoustic transducer

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR556412A (en) * 1923-05-09 1923-07-20 Const Electr De Lyon Et Du Dau Improvements to speaker phones
DE505407C (en) * 1924-12-13 1930-08-20 Aeg Apparatus for converting electrical energy into sound energy and vice versa
US2002189A (en) * 1927-04-22 1935-05-21 Rca Corp Acoustic device
DE599424C (en) * 1930-02-28 1934-07-02 Telefunken Gmbh Electrodynamic telephone or microphone
DE679439C (en) * 1935-04-10 1939-08-05 Pertrix Chem Fab Akt Ges Cone loudspeaker with electrodynamic drive system
US2238741A (en) * 1938-02-22 1941-04-15 Gen Electric Electrodynamic transducer
US2293078A (en) * 1939-12-05 1942-08-18 B A Proctor Company Inc Microphone
US2549963A (en) * 1945-12-03 1951-04-24 Hartford Nat Bank & Trust Co Electroacoustic transducer
US2537253A (en) * 1946-08-20 1951-01-09 Chris S Andersen Electrodynamic telephone receiver
FR936121A (en) * 1946-11-15 1948-07-09 Loudspeaker enhancements
US2534157A (en) * 1949-06-04 1950-12-12 Gen Electric Sound reproducing device

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3149254A (en) * 1961-08-07 1964-09-15 Thomas A Carter Linear motor or generator
US3246721A (en) * 1962-04-27 1966-04-19 Siemens Ag Frequency response of an electroacoustic transducer
DE1223421B (en) * 1962-07-31 1966-08-25 Dr Wolfgang Felix Ewald speaker
DE1201876B (en) * 1963-04-11 1965-09-30 Alexander Wiesbauer Centering and holding device for loudspeaker membranes, in particular flat membranes
US4757548A (en) * 1985-12-02 1988-07-12 Fenner Jr Thomas C Speaker system and dome-shaped enclosure therefor
US4843628A (en) * 1986-07-10 1989-06-27 Stanton Magnetics, Inc. Inertial microphone/receiver with extended frequency response
US5473700A (en) * 1993-11-24 1995-12-05 Fenner, Jr.; Thomas C. High gain acoustic transducer
US20150163572A1 (en) * 2013-12-05 2015-06-11 Apple Inc. Pressure Vent for Speaker or Microphone Modules
US9363587B2 (en) * 2013-12-05 2016-06-07 Apple Inc. Pressure vent for speaker or microphone modules

Also Published As

Publication number Publication date
GB698695A (en) 1953-10-21

Similar Documents

Publication Publication Date Title
KR102282417B1 (en) High quality electro-magnetic speaker with improved air gap accuracy
US3925626A (en) Dynamic speaker having dome diaphragm and basket frequency
US11095969B2 (en) Earphone including internal duct
US2778882A (en) Microphones
JPS6033147A (en) Protective structure in sounder device for vehicle
US1930915A (en) Acoustic device
JP2017158006A (en) headphone
US2293078A (en) Microphone
US4163877A (en) Housing for circuitry and loudspeaker of a magnetic locator shields and resiliently mounts the loudspeaker
US3783311A (en) Magnetic device for use in acoustic apparatus
US2379891A (en) Sound translating device
US2410806A (en) Submarine signal detector
US1844802A (en) Loud speaker adapted for automobile use
US2498825A (en) Moving coil transducer and enclosure
GB375538A (en) Loud speaker
US1631646A (en) Sound-reproducing apparatus
JPH0974599A (en) Speaker device
US2718272A (en) Dynamic microphone
US2791641A (en) Telephone receiver
US2910546A (en) Loud speaker assembly
US1855582A (en) Loud speaker
US3024323A (en) Inverted loud speaker
JPH04248799A (en) Speaker equipment
US1765257A (en) Loud-speaker
US3214714A (en) Electro-mechanical transducers