US3790724A - Electromagnetic microphone including at least one acoustic resistance - Google Patents
Electromagnetic microphone including at least one acoustic resistance Download PDFInfo
- 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
Links
- 230000005520 electrodynamics Effects 0.000 claims abstract description 24
- 238000004891 communication Methods 0.000 claims description 15
- 239000000696 magnetic material Substances 0.000 claims description 10
- 239000000463 material Substances 0.000 abstract description 10
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 238000013016 damping Methods 0.000 description 3
- 229910001369 Brass Inorganic materials 0.000 description 1
- 239000010951 brass Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
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)
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NL7105001A NL7105001A (fr) | 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 (fr) |
AT (1) | AT325692B (fr) |
FR (1) | FR2133693B1 (fr) |
GB (1) | GB1369377A (fr) |
NL (1) | NL7105001A (fr) |
Cited By (5)
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 (fr) * | 1998-03-03 | 1999-09-10 | Koninklijke Philips Electronics N.V. | Haut parleur a friction acoustique pour amortissement de resonance |
US6570995B2 (en) * | 2000-11-14 | 2003-05-27 | Sony Corporation | Speaker device |
Families Citing this family (3)
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)
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)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE971704C (de) * | 1953-06-25 | 1959-03-19 | Carl Ludwig Lehner | Elektroakustischer Wandler fuer telefonische Zwecke |
-
1971
- 1971-04-14 NL NL7105001A patent/NL7105001A/xx unknown
-
1972
- 1972-03-31 US US00240012A patent/US3790724A/en not_active Expired - Lifetime
- 1972-04-11 GB GB1661072A patent/GB1369377A/en not_active Expired
- 1972-04-11 AT AT312972A patent/AT325692B/de not_active IP Right Cessation
- 1972-04-13 FR FR7213007A patent/FR2133693B1/fr not_active Expired
Patent Citations (5)
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)
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 (fr) * | 1998-03-03 | 1999-09-10 | Koninklijke Philips Electronics N.V. | Haut parleur a friction acoustique pour amortissement de 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 |
ATA312972A (de) | 1975-01-15 |
GB1369377A (en) | 1974-10-09 |
FR2133693B1 (fr) | 1979-01-05 |
AT325692B (de) | 1975-11-10 |
NL7105001A (fr) | 1972-10-17 |
FR2133693A1 (fr) | 1972-12-01 |
DE2217051B2 (de) | 1976-09-02 |
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