US3790724A - Electromagnetic microphone including at least one acoustic resistance - Google Patents

Electromagnetic microphone including at least one acoustic resistance Download PDF

Info

Publication number
US3790724A
US3790724A US00240012A US3790724DA US3790724A US 3790724 A US3790724 A US 3790724A US 00240012 A US00240012 A US 00240012A US 3790724D A US3790724D A US 3790724DA US 3790724 A US3790724 A US 3790724A
Authority
US
United States
Prior art keywords
grooves
top plate
diaphragm
magnetic
air volume
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
US00240012A
Other languages
English (en)
Inventor
G Schenkel
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.)
US Philips Corp
Original Assignee
US Philips Corp
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 US Philips Corp filed Critical US Philips Corp
Application granted granted Critical
Publication of US3790724A publication Critical patent/US3790724A/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
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/222—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only  for microphones

Definitions

  • Each acoustic resistance comprises a groove which is pressed in a part of the magnet system made of a sintered material and is covered by a cover plate.
  • the invention relates to an electrodynamic microphone provided with a diaphragm to which a moving coil is attached which is suspended in the active air-gap of a magnet system, the volume of air behind the diaphragm being connected with at least one acoustic resistance.
  • the acoustic resistances take the form of damping materials disposed in ducts.
  • the damping materials may be provided in the form of plugs pressed from sintered granules.
  • the orifices of the ducts may be closed by pieces of gauge. This method of providing the damping materials is time-consuming and hence expensive to manufacture by mass production methods.
  • a microphone according to the invention is characterized in that the acoustic resistance comprises a narrow groove which is pressed in a part of the magnet system made of a sintered material and is covered by a cover plate.
  • the part of the magnet system made of a sintered material is manufactured by pressing. In the press operation the required number of grooves which act as acoustic resistances may simultaneously be formed.
  • the sintered material has the property that the pressed dimensions have very close tolerances.
  • the groove or grooves may be formed either in the upper surface or in the lower surface of the upper plate.
  • the active air-gap communicates with the air chamber provided in the magnet system between the core and the pot.
  • the core of a magnet system usually is centered with respect to the top plates by a centering member made of a non-magnetic material, the upper part of this member is advantageously given a flat shape so that it can serve as the cover plate for the groove or grooves.
  • FIG. 1 is a cross-sectional view of a microphone having an acoustic resistance according to the invention.
  • FIG. 2 shows two radial sections of this microphone.
  • FIG. 1 the microphone is of the electrodynamic type.
  • a diaphragm 1 provided with a moving coil 2 is movably arranged and secured to the magnet system along its edge 3.
  • the magnet system comprises a core 4 which is made of a permanent-magnetic material and is axially magnetized.
  • the core 4 is centrally disposed on a bottom 5 of a pot 6 made of a sintered material.
  • the pot 6 is closed by an upper plate 7 also made of a sintered material.
  • the top plate 7 together with a soft-iron plate 8 disposed on the core 4 defines an active air-gap 9 in which the moving coil 2 is free to move.
  • the top plate 7 has six radial grooves 10 formed in its upper surface which are covered by a flat brass ring 11. Through the grooves 10 the air volume 12 behind the diaphragm 1 communicates with the outside atmosphere. The edge of the diaphragm 1 is secured to the ring 11.
  • the lower surface of the top plate 7 also has six radial grooves 13 formed in it which are shifted by an angle of 30 with respect to the grooves 10.
  • Both the grooves 10 and the grooves 13 are spaced apart at angles of 60 to one another.
  • the grooves have a width of 1 mm and a depth of um.
  • the air volume 12 communicates via the air-gap 9 with an air chamber 14 defined by the core 4 and the pot 6.
  • the grooves 13 are closed by a flat upper surface 15 of a centering member 16 by which the core 4 is centered in the pot 6.
  • the centering member 16 is provided with a recess 17 to prevent the moving coil 2 from striking the centering member in the case of large deflections of the diaphragm.
  • An electrodynamic microphone comprising, a magnet system including a central core enclosed within a magnetic member having a top plate made of a sintered magnetic material and arranged to define an air gap with said core, a diaphragm having a movably mounted coil secured thereto and positioned so that the coil is disposed within said air gap of the magnet system, said diaphragm being mounted to define an air volume space with the top portion of the magnet system, said top plate having an upper surface and a lower surface with a plurality of narrow grooves formed in at least one surface and dimensioned so as to function as an acoustic resistance and being in communication with said air volume space behind the diaphragm, and a cover plate covering a portion of said grooves.
  • An electrodynamic microphone as claimed in claim 1 wherein said grooves are formed in the upper surface of the top plate so as to form an acoustic communication path between the air volume behind the diaphragm and the external atmosphere, and the cover plate comprises a ring which covers said grooves and is made of a non-magnetic material and to which the diaphragm is secured along its edge.
  • An electrodynamic microphone as claimed in claim 1 wherein said grooves are disposed radially about the central core in the upper surface of the top plate so as to form a plurality of acoustic communication paths between said air volume space and the external atmosphere.
  • An electrodynamic microphone as claimed in claim 1 wherein said core and magnetic member are disposed so as to form together an annular air chamber and wherein said grooves are radially disposed about the central core in the lower surface of the top plate so as to form a plurality of acoustic communication paths between said air volume space and the air chamber.
  • central core comprises a cylindrical axially magnetized permanent magnet and said magnetic member comprises a sintered pot core.
  • An electrodynamic microphone as claimed in claim 1 wherein said core and magnetic member are disposed so as to form together an annular air chamber and said grooves are radially disposed in both the upper and lower surfaces of the top plate with the grooves in the upper surface angularly offset from the grooves in the lower surface, the grooves in the upper surface forming a plurality of acoustic communication paths between the air volume space and the external atmosphere and the grooves in the lower surfaceforming a second plurality of acoustic communication paths between the air volume space and said annular air chamher.
  • An electrodynamic microphone comprising, a magnetic circuit including a cylindrical central magnetic core enclosed by a magnetic pot core having an annular top plate made of a sintered magnetic material and arranged to define an air gap with said central core, at least one element of said magnetic circuit being permanently magnetized to produce a magnetic field in the air gap, a vibratory system including a diaphragm having a movably mounted coil secured thereto and positioned so that the coil is disposed within said air gap, said diaphragm being positioned to define an air vol ume space with the top part of the magnetic circuit,
  • said top plate including a plurality of narrow grooves dimensioned to function as an acoustic resistance in communication with the air volume space behind the diaphragm, and a cover plate covering a portion of said grooves to form therewith a plurality of tubular ducts.
  • An electrodynamic microphone as claimed in claim 9 wherein said cover plate comprises a nonmagnetic ring adjacent the upper surface of the top plate and the grooves are radially disposed in the upper surface of said top plate.

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)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
US00240012A 1971-04-14 1972-03-31 Electromagnetic microphone including at least one acoustic resistance Expired - Lifetime US3790724A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL7105001A NL7105001A (de) 1971-04-14 1971-04-14

Publications (1)

Publication Number Publication Date
US3790724A true US3790724A (en) 1974-02-05

Family

ID=19812916

Family Applications (1)

Application Number Title Priority Date Filing Date
US00240012A Expired - Lifetime US3790724A (en) 1971-04-14 1972-03-31 Electromagnetic microphone including at least one acoustic resistance

Country Status (5)

Country Link
US (1) US3790724A (de)
AT (1) AT325692B (de)
FR (1) FR2133693B1 (de)
GB (1) GB1369377A (de)
NL (1) NL7105001A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3937905A (en) * 1972-07-25 1976-02-10 Manger J W Moving voice coil transducer having a flat diaphragm of an impregnated knit
US4013846A (en) * 1975-08-28 1977-03-22 Minnesota Mining And Manufacturing Company Piston loudspeaker
US4752963A (en) * 1985-06-12 1988-06-21 Kabushiki Kaisha Kenwood Electroacoustic converter having a recessed step on the center pole
WO1999045742A1 (en) * 1998-03-03 1999-09-10 Koninklijke Philips Electronics N.V. A loudspeaker featuring acoustic friction to damp resonance
US6570995B2 (en) * 2000-11-14 2003-05-27 Sony Corporation Speaker device

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2134745B (en) * 1983-02-04 1986-10-22 Standard Telephones Cables Ltd Electro acoustic tranducer
AT382281B (de) * 1984-11-15 1987-02-10 Akg Akustische Kino Geraete Kreisringfoermige membran, insbesondere fuer mikrophone und kopfhoerer
DE3700594A1 (de) * 1986-01-16 1987-07-23 Akg Akustische Kino Geraete Druckgradientenempfaenger

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1941073A (en) * 1931-08-12 1933-12-26 Bell Telephone Labor Inc Pneumatic sound reproducer
GB812348A (en) * 1954-06-03 1959-04-22 Leonard Walter Murkham Improvements in and relating to electro magnetic transducers
US3240883A (en) * 1961-05-25 1966-03-15 Shure Bros Microphone
GB1037244A (en) * 1964-02-20 1966-07-27 Standard Telephones Cables Ltd Improvements in or relating to moving coil transducers
US3581015A (en) * 1966-12-28 1971-05-25 Aiwa Co Dynamic microphone

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE971704C (de) * 1953-06-25 1959-03-19 Carl Ludwig Lehner Elektroakustischer Wandler fuer telefonische Zwecke

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1941073A (en) * 1931-08-12 1933-12-26 Bell Telephone Labor Inc Pneumatic sound reproducer
GB812348A (en) * 1954-06-03 1959-04-22 Leonard Walter Murkham Improvements in and relating to electro magnetic transducers
US3240883A (en) * 1961-05-25 1966-03-15 Shure Bros Microphone
GB1037244A (en) * 1964-02-20 1966-07-27 Standard Telephones Cables Ltd Improvements in or relating to moving coil transducers
US3581015A (en) * 1966-12-28 1971-05-25 Aiwa Co Dynamic microphone

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3937905A (en) * 1972-07-25 1976-02-10 Manger J W Moving voice coil transducer having a flat diaphragm of an impregnated knit
US4013846A (en) * 1975-08-28 1977-03-22 Minnesota Mining And Manufacturing Company Piston loudspeaker
US4752963A (en) * 1985-06-12 1988-06-21 Kabushiki Kaisha Kenwood Electroacoustic converter having a recessed step on the center pole
WO1999045742A1 (en) * 1998-03-03 1999-09-10 Koninklijke Philips Electronics N.V. A loudspeaker featuring acoustic friction to damp resonance
US6570995B2 (en) * 2000-11-14 2003-05-27 Sony Corporation Speaker device

Also Published As

Publication number Publication date
DE2217051A1 (de) 1972-10-26
DE2217051B2 (de) 1976-09-02
NL7105001A (de) 1972-10-17
FR2133693B1 (de) 1979-01-05
ATA312972A (de) 1975-01-15
AT325692B (de) 1975-11-10
FR2133693A1 (de) 1972-12-01
GB1369377A (en) 1974-10-09

Similar Documents

Publication Publication Date Title
US5905805A (en) Electrodynamic transducer
US7477757B2 (en) Dual-gap transducer with radially-charged magnet
US4337379A (en) Planar electrodynamic electroacoustic transducer
US3919498A (en) Electroacoustic transducer
US3790724A (en) Electromagnetic microphone including at least one acoustic resistance
US3830986A (en) Magnetic circuit for an electro-acoustic converter
US3614335A (en) Electroacoustic transducer held together by thermoplastic clamping ring
US2249160A (en) Acoustic device
US3763334A (en) Magnet assembly
US2506624A (en) Electroacoustic transducer
US3581015A (en) Dynamic microphone
US3258543A (en) Dynamic microphone
US3079472A (en) Magnetic field structure for transducers and method of constructing same
US2535757A (en) Peripherally driven electroacoustical transducer
US2249158A (en) Electroacoustic transducer
US11553279B1 (en) Electromagnetic transducer and loudspeaker
US1630380A (en) Loud-speaker unit
US3549830A (en) Magnet configuration for a loudspeaker
US3296386A (en) Magnetic system for electrodynamic transducers
US2506609A (en) Ring armature telephone receiver
US1838027A (en) Electrodynamic device
US2171733A (en) Acoustic device
US3851118A (en) Electroacoustic transducer having a preformed non-magnetic gentering sleeve
US2202886A (en) Microphone
US2522530A (en) Electroacoustic transducer