US2549963A - Electroacoustic transducer - Google Patents

Electroacoustic transducer Download PDF

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Publication number
US2549963A
US2549963A US721636A US72163647A US2549963A US 2549963 A US2549963 A US 2549963A US 721636 A US721636 A US 721636A US 72163647 A US72163647 A US 72163647A US 2549963 A US2549963 A US 2549963A
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US
United States
Prior art keywords
air
channels
diaphragm
space
pole
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
US721636A
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English (en)
Inventor
Boer Jan De
Schenkel Gerrit
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Hartford National Bank and Trust Co
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Hartford National Bank and Trust Co
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Publication date
Application filed by Hartford National Bank and Trust Co filed Critical Hartford National Bank and Trust Co
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Publication of US2549963A publication Critical patent/US2549963A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/02—Details
    • H04R9/025—Magnetic circuit
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type

Definitions

  • the invention relates to an oscillatory system, more particularly an electrodynamic system, for example for microphones, loudspeakers, pickups, and so forth, comprising a diaphragm which, together with the air cushion located between this diaphragm and the magnet system and through one or more apertures located behind this diaphragm and filled with damping material, is acoustically coupled with a space located behind the apertures.
  • an oscillatory system more particularly an electrodynamic system, for example for microphones, loudspeakers, pickups, and so forth, comprising a diaphragm which, together with the air cushion located between this diaphragm and the magnet system and through one or more apertures located behind this diaphragm and filled with damping material, is acoustically coupled with a space located behind the apertures.
  • the damping material forms channels parallel to the air motion occurring in the apertures during operation. This ensures damping of the system resonance lying in the range of the lower frequencies, which is more efficient than that hitherto obtainable by the conventional damping methods. This effect is probably due to the fact that with the arrangement of the channels as described, there is an air resistance which is larger in value than in.
  • the mass of the system is enlarged, as is known per se, by a proper choice of the total section of the channels, so that in addition to more efiicient damping, an extension of the frequency characteristic curve towards the region of the lowest frequency ensues.
  • the channels may, for example, be constituted by spaces between bars coaxially arranged in the aperture. It has been found that, for example, metal bars give highly satisfactory results. This is probably due to the fact that frictional heat provoked by the air motion in the channels is conducted away more efficiently by metal bars. and this acts on the resistance to the air in these channels.
  • the invention is particularly suitable for use in electrodynamic oscillatory systems provided with a central pole core, since use can be made with advantage of the presence of this core to arrange the said apertures in a central bore in this core.
  • the apertures filled with damping material communicate with a space sealed from the open air, so that a so-called pressure microphone is obtained.
  • the said apertures communicate directly with the open air, so that a so-called pressure-gradient microphone is formed.
  • Fig. 1 shows diagrammatically an electrodynamic pressure microphone, of which the bore in the core of the system is filled with coaxially arranged bars.
  • the particular form of the air channels may be seen from section A--A in Fig. la. V
  • Fig. 2 shows the frequency characteristic curve
  • Fig. 3 the electrical equivalent circuit of the pressure microphone shown in Fig. 1.
  • Fig. 4 represents diagrammatically an electrodynamic pressure-gradient microphone, in which the bore in the core of the system is filled with coaxial bars.
  • Fig. 5 shows the electrical equivalent circuit of the microphone shown in Fig. 4.
  • a coil I fastened to a diaphragm 2 oscillates under the influence of the sound pressure in the magnetic field in an air gap 3 formed by a pole core 4 and a pole plate 5.
  • the field is produced by an annular magnet 6.
  • a space 1 located directly behind the diaphragm serves as an air cushion between the diaphragm 2 and the core 4 and communicates with a space H] by means of the air gap 3 and an annular gap 8 formed by the pole plate 5 and a ring 9 of nonmagnetic material.
  • core 4 is provided with a bore II which is filled with coaxial bars [2, so that channels l3 are formed which connect the space 1 to a space 14.
  • the channels concerned may be formed in a simple manner by axially inserting, in the said bore a ribbon of corrugated metal coiled so as to form a cylinder, the diameter of which fits the bore.
  • Space M and the air channels 13 provided, according to the invention, in the central bore ll of the magnet core 4 are critical for the reproduction of oscillations having frequencies less than 600 c./s. It will be seen from Fig. la how these channels ars formed. As soon as the system formed by diaphragm 2, air channels 13 and space M is caused to be in resonance, both the mass of the diaphragm and the mass of the air in the narrow channels are added up, as are also the rigidity of the edge of the diaphragm and the rigidity of the air in [4, owing to which a resonance in the range of the lowest frequencies to be reproduced is produced which, however, is damped by the heavy resistance to the moving mass of air in the narrow channels; this is designated l8 in Fig. 2.
  • Fig. 3 shows an equivalent electrical circuit of the system described, the masses, rigidities and resistances being indicated in known manner as inductances, capacities and resistances. Connected in series with the mass l9 and the rigidity of diaphragm 2 are successively:
  • Fig. 4 represents an electrodynamic pressuregradient microphone," whose equivalent circuit is shown in Fig. 5.
  • behind diaphragm 32 communicates directly with the open air through channels 33 between bars 35 coaxially arranged in the bore 3:1 of core 35. Space 3'! is fully closed by a ring 38 of non-magnetic material.
  • the coil 39 fastened to diaphragm 32 oscillates in the air gap between pole core 35 and pole plate 40.
  • the field is produced by an annular magnet 4
  • the invention may successfully be used not only for microphones and loudspeakers but for any kind of oscillatory system, the resonance frequency of which should be damped and also shifted towards the lower frequencies with respect to the case in which the measures according to the invention are not used.
  • An electrodynamic transducer comprising a magnetic structure defining an air gap and including a center pole, and a vibratory system including a diaphragm and a coil attached thereto and surrounding said center pole within said air gap to define an air cushion between said diaphragm and one end of said center pole, said center pole having a plurality of longitudinal channels therein communicating between said air cushion and an air space at the other end of said pole, whereby said diaphragm is acoustically coupled through said air cushion and the air contained within said channels to said air space, the total sectional area of said channels 4 having a value at which the mass of the air in the channels and the air friction of said channels imparts a predetermined acoustic resonance characteristic to said vibratory system.
  • a transducer as set forth in claim 1 further including means secured to said magnetic structure to enclose the air space at the other end of said pole piece.
  • An electrodynamic transducer comprising a magnetic structure defining an air gap and including a center pole, and a vibratory system including a diaphragm and a coil attached thereto and surrounding said center pole within said air gap to define an air cushion between said diaphragm and one end of said center pole, said center pole having a bore therein and a plurality of rods in parallel juxtaposition arranged within said core to define a plurality of relatively narrow longitudinal channels cornrnunieating between said air cushion and an air space at the other end of said pole, whereby said diaphragm is acoustically coupled through said air cushion and the air contained within said channels to said air space, the total sectional area of said channels having a value at which the mass of the air in the channels and the air friction of said channels imparts a predetermined acoustic resonance characteristic to said vibratory system.
  • An electrodynarnic transducer comprising a reentrant magnetic structure including a center pole and a plate pole arranged to define a magnetic flux air gap, a vibratory system includin a diaphragm and a coil attached thereto and surrounding said center pole within said air gap to define an air cushion, and a nonmagnetic annular member supported by said center pole below said plate pole to define an annular air gap communicating between said magnetic flux air gap and the air chamber formed within said magnetic structure, said center pole having a plurality of longitudinal channels therein communicating between said air cushion and an air space at the other end of said poles whereby said diaphragm is acoustically coupled through said air cushion and the air contained within said channels to said air space, the total sectional area of said channels having a value at which the mass of air in the channels and the air friction of said channels imparts a predetermined acoustic resonance characteristic to said vibratory system.
  • An electrodynamic transducer as set forth in claim 4 further including a cuphaped member secured to the end of said reentrant magnetic structure opposing said plate pole for enclosing said air space.
  • An electrodynamic transducer comprising. a
  • reentrant magnetic structure including a center pole and a plate pole arranged to define a magnetic flux air gap, a vibratory system including a diaphragm and a coil attached thereto and surrounding said center pole within said air gap to define an air cushion, and a nonmagnetic annular member supported by said center pole below said plate pole and peripherally connected to said plate pole to form an enclosed air chamber within said magnetic structure, said center pole having a plurality of longitudinal channels therein communicating between said air cushion and an air space at the other end of said poles whereby said diaphragm is acoustically coupled through said air cushion and the air contained within said channels to said air space, the total sectional area of said channels having a value at which the mass of air in the channels and the air friction of said channels imparts a predetermined acoustic resonance characteristic to said vibratory system.
  • An acoustic transducer comprising a magnetic structure including a pole member, and a vibratory system including a diaphragm adjacent one end of said pole member to define an air cushion therebetween, said pole member having a plurality of longitudinal channels therein communicating between said air cushion and an air space at the other end of said pole member,
  • said diaphragm is acoustically coupled through said air cushion and the air contained within said channels to said air space.
  • An acoustic transducer comprising a magnetic structure including a pole member, and a vibratory system including a diaphragm adjacent one end of said pole member to define an air cushion therebetween, said pole member having a bore therein and a plurality of rods disposed in parallel juxtaposition forming a plurality of relatively narrow longitudinal channels communicating between said cushion and an air space at the other end of said pole member, whereby said diaphragm is acoustically coupled through said cushion and the air in said channels to said air space.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
US721636A 1945-12-03 1947-01-11 Electroacoustic transducer Expired - Lifetime US2549963A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL122255 1945-12-03

Publications (1)

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US2549963A true US2549963A (en) 1951-04-24

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US721636A Expired - Lifetime US2549963A (en) 1945-12-03 1947-01-11 Electroacoustic transducer

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US (1) US2549963A (US07166745-20070123-C00016.png)
DE (1) DE836497C (US07166745-20070123-C00016.png)
FR (1) FR936416A (US07166745-20070123-C00016.png)
NL (1) NL67077C (US07166745-20070123-C00016.png)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2761912A (en) * 1951-05-31 1956-09-04 Martin L Touger Sound translating apparatus
US2773130A (en) * 1953-03-31 1956-12-04 Rca Corp Acoustical resistance for pressure type microphones
US2778882A (en) * 1951-01-11 1957-01-22 Lustraphone Ltd Microphones
US2838607A (en) * 1951-04-27 1958-06-10 Rca Corp Combination chassis and loudspeaker
US2848561A (en) * 1953-06-02 1958-08-19 Akg Akustische Kino Geraete Dynamic microphone
US2858377A (en) * 1953-04-29 1958-10-28 Arthur Blumenfeld Driver unit for loudspeakers
US2923783A (en) * 1957-06-17 1960-02-02 Stanley F White Electro-acoustical transducer
DE1079997B (de) * 1954-06-29 1960-04-14 Kockums Mek Verkst S Aktiebola Druckmittelbetriebener Schallerzeuger
US3079471A (en) * 1961-03-01 1963-02-26 Ampex Loudspeaker
US3085847A (en) * 1956-02-16 1963-04-16 Massa Division Of Cohu Electro Direct recording oscillograph
US3115207A (en) * 1954-01-11 1963-12-24 Electro Voice Unidirectional microphone
US3157750A (en) * 1960-07-15 1964-11-17 Akg Akustische Kino Geraete Dynamic headphone
US3581015A (en) * 1966-12-28 1971-05-25 Aiwa Co Dynamic microphone
US3662124A (en) * 1967-06-05 1972-05-09 Willco Horgerate Medizinische Directional microphone for hearing aid
US4379952A (en) * 1979-12-11 1983-04-12 U.S. Philips Corporation Mechanical filter for an electrodynamic transducer
WO1989004106A1 (en) * 1987-10-28 1989-05-05 Acs Communications, Inc. Acoustic filter microphone cup
US20100034411A1 (en) * 2008-08-08 2010-02-11 Nokia Corporation Apparatus incorporating an adsorbent material, and methods of making same

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB956448A (en) * 1959-06-24 1964-04-29 Philips Electrical Ind Ltd Improvements in or relating to electrodynamic microphones
FR85403E (fr) * 1963-07-16 1965-08-06 Geophysique Cie Gle Perfectionnements aux vibrateurs électro-mécaniques
DE2503828C3 (de) * 1975-01-30 1983-04-21 Friedrich Reiner Telefonfabrik Permanentdynamische elektroakustische Wandlerkapsel
DE3016385A1 (de) * 1980-04-29 1981-11-05 Realton-Gesellschaft für neuartige Musikinstrumente mbH & Co KG, 5350 Euskirchen Vorrichtung zur umwandlung eines ein nutzsignal bildenden staudruckes in eine elektriche groesse

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1634380A (en) * 1922-04-21 1927-07-05 Nayler William Edwin Sound box for gramophones and similar instruments
US1957765A (en) * 1934-05-08 Magnetomotive force circuits
US1964606A (en) * 1932-04-12 1934-06-26 Bell Telephone Labor Inc Acoustic device
US2197649A (en) * 1936-11-14 1940-04-16 Cinaudagraph Corp Loudspeaker and method of formation
US2295483A (en) * 1934-06-04 1942-09-08 Jensen Radio Mfg Company Loudspeaker
US2312238A (en) * 1938-01-27 1943-02-23 Rca Corp Dynamic loud-speaker
US2367026A (en) * 1941-08-06 1945-01-09 Rock Ola Mfg Corp Electrodynamic speaker
US2395166A (en) * 1942-12-24 1946-02-19 Astatic Corp Transducer
US2429470A (en) * 1934-06-04 1947-10-21 Jensen Mfg Company Loud-speaker with pressure-equalized chamber system enclosing flux gap

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1957765A (en) * 1934-05-08 Magnetomotive force circuits
US1634380A (en) * 1922-04-21 1927-07-05 Nayler William Edwin Sound box for gramophones and similar instruments
US1964606A (en) * 1932-04-12 1934-06-26 Bell Telephone Labor Inc Acoustic device
US2295483A (en) * 1934-06-04 1942-09-08 Jensen Radio Mfg Company Loudspeaker
US2429470A (en) * 1934-06-04 1947-10-21 Jensen Mfg Company Loud-speaker with pressure-equalized chamber system enclosing flux gap
US2197649A (en) * 1936-11-14 1940-04-16 Cinaudagraph Corp Loudspeaker and method of formation
US2312238A (en) * 1938-01-27 1943-02-23 Rca Corp Dynamic loud-speaker
US2367026A (en) * 1941-08-06 1945-01-09 Rock Ola Mfg Corp Electrodynamic speaker
US2395166A (en) * 1942-12-24 1946-02-19 Astatic Corp Transducer

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2778882A (en) * 1951-01-11 1957-01-22 Lustraphone Ltd Microphones
US2838607A (en) * 1951-04-27 1958-06-10 Rca Corp Combination chassis and loudspeaker
US2761912A (en) * 1951-05-31 1956-09-04 Martin L Touger Sound translating apparatus
US2773130A (en) * 1953-03-31 1956-12-04 Rca Corp Acoustical resistance for pressure type microphones
US2858377A (en) * 1953-04-29 1958-10-28 Arthur Blumenfeld Driver unit for loudspeakers
US2848561A (en) * 1953-06-02 1958-08-19 Akg Akustische Kino Geraete Dynamic microphone
DE1073545B (de) * 1953-06-02 1960-01-21 Akustische u Kino Gerate Ges mbH, Wien Dynamisches Rieht mikrophon
US3115207A (en) * 1954-01-11 1963-12-24 Electro Voice Unidirectional microphone
DE1079997B (de) * 1954-06-29 1960-04-14 Kockums Mek Verkst S Aktiebola Druckmittelbetriebener Schallerzeuger
US3085847A (en) * 1956-02-16 1963-04-16 Massa Division Of Cohu Electro Direct recording oscillograph
US2923783A (en) * 1957-06-17 1960-02-02 Stanley F White Electro-acoustical transducer
US3157750A (en) * 1960-07-15 1964-11-17 Akg Akustische Kino Geraete Dynamic headphone
US3079471A (en) * 1961-03-01 1963-02-26 Ampex Loudspeaker
US3581015A (en) * 1966-12-28 1971-05-25 Aiwa Co Dynamic microphone
US3662124A (en) * 1967-06-05 1972-05-09 Willco Horgerate Medizinische Directional microphone for hearing aid
US4379952A (en) * 1979-12-11 1983-04-12 U.S. Philips Corporation Mechanical filter for an electrodynamic transducer
WO1989004106A1 (en) * 1987-10-28 1989-05-05 Acs Communications, Inc. Acoustic filter microphone cup
US20100034411A1 (en) * 2008-08-08 2010-02-11 Nokia Corporation Apparatus incorporating an adsorbent material, and methods of making same
US8630435B2 (en) * 2008-08-08 2014-01-14 Nokia Corporation Apparatus incorporating an adsorbent material, and methods of making same

Also Published As

Publication number Publication date
FR936416A (fr) 1948-07-20
DE836497C (de) 1952-04-15
NL67077C (US07166745-20070123-C00016.png)

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