US3061690A - Acoustically compensated microphone with adjustable acoustic resistance - Google Patents

Acoustically compensated microphone with adjustable acoustic resistance Download PDF

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US3061690A
US3061690A US76098558A US3061690A US 3061690 A US3061690 A US 3061690A US 76098558 A US76098558 A US 76098558A US 3061690 A US3061690 A US 3061690A
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microphone
diaphragm
cavity
means
vent tube
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Swinehart Frank
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TURNER CO
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TURNER CO
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00Details of transducers, loudspeakers or microphones
    • H04R1/20Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only
    • H04R1/222Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only for microphones

Description

Oct. 30, 1962 F. swlNEHART 3,061,690 ACOUSTICALLY COMPENSATED MICROPHONE WITH ADJUSTABLE ACOUSTIC RESISTANCE 5 Sheets-Sheet 1 Filed Sept. l5, 1958 OQ Q .Q Y NQ I I I l u.:

r x L l t ll Il lll,--.

Oct. 30, 1962 F. swlNEl-IART 3,061,690

ACOUSTICALLY COMPENSTED MICROPHONE WITH ADJUSTABLE ACOUSTIC RESISTANCE Filed Sept. 15, 1958 3 Sheets-Sheet 2 lqooo/v 20,950

Oct. 30, 1962 F. swim-:HART 3,061,690

ACOUSTICALLY COMPENSATED MICROPHONE WITH ADJUSTABLE ACOUSTIC RESISTANCE Filed Sept. l5, 1958 5 Sheets-Sheet 5 l arent 3,061,696 Patented Oct. 30, 1962 tice ACOUSTICALLY COIPESATED MICRRHONE WITH ADJUSTABLE ACOUSTIC RESISTANIE Frank Swinehart, Cedar Rapids, Iowa, assignor to 'I he Turner Company, Cedar Rapids, Iowa, a corporation of Iowa Filed Sept. 15, 1958, Ser. No. 760,995 13 Claims. (Cl. 179-1155) This invention relates to a dynamic lavalier microphone. More particularly, this invention relates to a microphone of the type which has a diaphragm-mounted voice coil which moves in the field of a permanent magnet and which is constructed so as to be adapted to be worn on a neck cord from which the microphone is suspended and positioned near the body of the user as at his chest.

The size and type of construction required for the normal manner and position of use of lavalier microphones has in the past resulted in considerable ditiiculty in achieving the desired quality of audio output from them. Even though an appropriate balance between high and low frequencies was achieved, lavalier microphones have in the past had a tight or boXy quality in the sound reproduced from them. It has been found that this diiculty can be overcome in an otherwise properly constructed lavalier microphone by tuning or resonating the back cavity thereof by a vent tube `which has been found to be most effective when its open end is near the top or front of the microphone. By this means in conjunction with other features to be described below, it has been found possible to eliminate the tight or boxy quality of the sound from a lavalier microphone and to achieve the pleasing and natural sound quality desired.

It is therefore an object of this invention to provide an improved dynamic lavalier microphone.

It is a further object of this invention to provide a dynamic lavalier microphone wherein the back cavity is tuned by a vent tube opening to the front of the microphone.

It is a further object of this invention to provide a dynamic lavalier microphone wherein the over-all frequency response is such as to compensate for the fact that the microphone is used near the body.

Other objects, features, and advantages of the present invention will be more fully apparent from the followingy detailed description taken in connection with the accompanying drawings in which like reference characters have been used to refer to like parts throughout and wherein:

FIGURE 1 is a longitudinal sectional view showing a lavalier microphone constructed and assembled in accordance with the present invention.

FIGURE 2 is an end View of the front or top of the microphone of FIGURE l.

FIGURE 3 is a detailed sectional view of a member inserted in the case of the microphone of FIGURE 1 to form the vent tube.

FIGURE 4 is a detailed sectional view of the interior or voice coil and magnet assembly of the microphone shown in FIGURE 1.

FIGURE 5 is a plan view of an inner grille member included in the microphone of FIGURE 1.

FIGURE 6 is a schematic wiring diagram of the microphone of FIGURE l.

FIGURE 7 is a graph of the frequency response of the microphone of FIGURE l wherein frequency in cycles per second is plotted as abscissa and response in decibels is plotted as ordinate.

FIGURE 8 is an exploded view of the component parts of the microphone of FIGURE 1.

Turning now to the drawings, there is shown in FIG- has mating exterior threads on an indented shoulder thereof. The case member 10 has a top or front section Itia of enlarged cross-sectional diameter on the interior of which is formed a first shoulder 10b and a second shoulder 10c. It will be noted from FIGURE l that the case member terminates at its front or top end in a lip or ange member 10d which projects forwardly and that the first shoulder member 10b extends inwardly from this ange member 10d. The portion 10a of the case member between the first shoulder 10b and the second shoulder Itis has an interior diameter which is intermediate between that of the interior diameter of flange 10d and of the main portion of the case. The shoulder 10c extends inwardly from this intermediate diameter and merges with the main portion of the case member.

Seated on the second shoulder 10c is an insert member 12 as shown in FIGURE l and as shown in greater detail in FIGURE 3. Insert member 12 is a round sleeve of metal having a spiral groove 13 cut on the inner surface thereof. The spiral groove 13 terminates in an inlet 13a which is positioned in the forward or front part of the casing section 10a and in an outlet 13b positioned adjacent the second shoulder in the casing 10. The metal sleeve 13 carrying groove 13a has an outer diameter equal to the inner diameter of the enlarged section 10a of the casing 16 and seats against the second shoulder 10c in the casing.

A tubular sleeve member 14 having an outer diameter equal to the smallest inner diameter of the sleeve member 1.2 is tightly fitted or pressed inside of the sleeve member to close the spiral groove in the sleeve member and thereby form the vent tube. It will be noted that the tube 14 is longer than the sleeve 12 and projects forwardly of it. The exterior surface of this forwardly projecting portion of the tube 14 is threaded as at 15 and receives in threaded engagement therewith a front frame member I6 which projects forwardly of the flange 10d on casing It? and terminates in an inwardly projecting shoulder portion 16a. Resting in back of the shoulder 16a is the outer grille 17 bearing a name plate 18. In back of the outer grille an inner grille 19 is positioned in sandwiched relation between a pair of sealing washers 20 and ZI. The inner grille 19 is shown in plan view in FIGURE 5 and comprises a circular plate having a plurality of openings therein as shown.

In back of the sealing washer 21 is positioned the interior assembly which for clarity of illustration is indicated by the general reference character 22 in FIG- URE 1 and is shown in greater detail in FIGURE 4.

Interior 22 comprises a magnet 23 having a pole piece 24 which is mounted in a yoke 25 by means of a machine screw 26. A grounding lug 27 is conveniently seated under screw 26 whereas other lugs such as 30 may be attached to the yoke by screws 28, 29 and insulating member 31. It will be noted that a portion of the pole piece is exteriorly threaded as at 32 and receives a retaining ring 33 which is interiorly threaded to be mounted thereon. A felt ring 34 is mounted between retaining ring 33 and a stator plate 35 which is shaped to iit over the end of yoke 25 and has a central opening through which the magnet pole protrudes. The annular space 36 between the edges of this opening and the magnet pole receives the voice coil 37 which, for clarity of illustration is shown in FIGURE 4 in disassembled position. Voice coil 37 is attached to diaphragm 38 which is supported by diaphragm ring 39 which in turn rests on stator plate 35. The diaphragm ring 39 may conveniently be affixed to thestator plate by means of a bead of cement around the outer diameter of the diaphragm rmg.

As may be seen in FIGURE l, the stator plate and diaphragm assembly are held in supported relationship against sealing washer 21 by means of another sealing washer 40 which abuts on one side against the end of tube 14 and on the other side underneath the shoulder formed by the stator plate 35 projecting down over the yoke 25. Front member 16 threadedly engages tube 14 to retain this assembly in position.

The Lback cavity of the microphone is formed by the net enclosed volume behind the sealing washer 40. It is important that all mechanical joints be tight in that leakage will impair the effectiveness of the resonance established between this back cavity and the vent tube formed by groove 13. The outlet 13b of vent tube 13 opens to the back cavity through the space between tube 14 and shoulder i100. The inlet 13C of vent tube 13 opens to a passage formed between the inner surface of the portion 10a of the casing 10 and the outer surface of the front support member 16 which is threadedly received in position on tube 14 after the interior assembly has been positioned on sealing washer 40 on the end of tube 14. The end of this passageway from the vent tube is covered by a vent grille 41 which seats in the first shoulder 10b of the outer casing member and is provided with a central aperture to snugly receive the front member `16. The sequence and mode of assembly of the parts may be seen more clearly by reference to the exploded view of FIGURE 8.

A transformer 42 4is positioned in case 10 in back of the interior assembly 22. The transformer may conveniently be mounted in the case by sponge rubber packing `43 which surrounds it to prevent shock and vibration. The forward wall 43C of this packing defines the rear wall of the back cavity. The space between the transformer 42 and the rear of the interior `22 which extends substantially down `to the second shoulder 10c is preferably packed lightly with spun ber glass insulation 44. Such spun fiber glass insulation `44 is preferably also lightly packed in back of `the vent grille 35 down to the inlet end of the spiral groove vent tube 13.

The electrical connections to and from the voice coil transformer 42 to the microphone and shielded cable 45 are conventional and are shown in the assembly view of FIGURE l and in the schematic wiring diagram of FIGURE 6. The cable 45 may enter the plug member 11 .through rubber tubing `46 held in position by a grommet y47 which in turn is held in plug 11 by a pressure plate 48 attached to the plug 11 by any convenient means such as screws to which lugs may also be attached as shown. Y

Referring `to FIGURE 8 it will be noted that the shield of cable 45 is directly connected by a wire 50 to the center lug 30 on the interior 22 thereby grounding its yoke. The three conductors 1, 52 and 53 of the cable 45 are respectively connected to the two ends and the center tap of the primary winding `of transformer 42, The secondary Winding of transformer 42 is of course connected by wires y54 and 55 to lugs on the interior assembly which in turn are connected to the voice coil in the usual manner.

In use, the microphone may be positioned in any convenient holder to which a neck cord may be attached to support `the microphone near the body of the user. The enlarged portion a of the casing terminating in the narrowing section which forms the shoulder 10c aords on the exterior of the casing a convenient shoulder or stop means which permits the microphone to be inserted and retained in such a holder. The over-all frequancy response of the microphone is selected to help compensate for the fact that the microphone is to be used near the body. A preferred exemplary frequency response is shown in the graph of FIGURE 7 wherein frequency in cycles per second is plotted as abscissa against response in decibels plotted as ordinate. In general terms, it may be stated that the desired frequency response is a smooth curve which has the medium and high frequencies from four to six decibels above the low frequencies. In particular, the cavity in back of the interior, which, to a large extent, controls the =low frequency response of the unit (below 200 cycles) is dimensioned so as to be resonant with the vent tube at approximately 70 cycles. Furthermore, the open end of the vent tube is arranged in such a ways as to take best advantage of its functioning. That is to say, the open end is positioned near the front of the unit and the low frequency sound enters the microphone primarily through this vent tube. Extensive tests have shown that even though the balance between the high and the low frequencies shown in FIGURE 7 was achieved, `the tight or boxy quality of prior art lavalier microphones persists if the vent tube is not used. It was only after the back cavity was tuned by a vent tube (in one exemplary embodiment having a cross-sectional area of approximately 0.014 square inch and a length along the spiral groove of approximately 8 inches) that the desired pleasing and natural quality of sound was achieved. Experiments have also shown that the vent tube is most effective when its open end is near the top of the microphone.

In operation, the sound in addition to directly actuating the diaphragm 39 and voice coil 37 also passes through the vent grille `41 and enters the inlet 13a of the vent tube 13. The sound is carried down the rest of the length of the vent tube spirally arranged around the interior 22 and enters the back cavity through the outlet 13b of the vent tube near the shoulder 10c and behind the diaphragm. The purpose of the spun glass `44 and 44a is to smooth out the frequnency response of the unit.

The resonant frequency of the back cavity is determined bythe enclosed volume -of the cavity and .the length and crosssection of the vent tube. This relationship may be expressed in terms of the electrical equivalent as follows:

Fres.:

The resonant frequency of the cavity-vent tube system can also be determined by this same relationship; the L terms being determined by the length and cross-sectional area of :the vent tube and the C term being determined by the cavity.

It has been experimentally found that if the interior 22 is mounted in a 'sealed cavity, that is, Without a vent tube to resonate it, the frequency response will show that the microphone starts to llose output at about 300 cycles. As the frequency is lowered, the response continues to fall so that the quality of the sound is impaired. The resonant back cavity-vent tube system overcomes this defect. Furthermore, if the interior 22 is mounted as shown in FIGURE l, but without the inner `grille 19, the response will show a serious loss above about 4000 or 5000 cycles. It is, then, the back resonant cavity-vent tube system, the interior itself, and the inner grille which determines over-all performance of this microphone. The external shape also has an influence upon this performance. Fur lthermore, by adjusting the retainer ring 33 shown in FIGURE 4 which compresses the felt ring 34, it is possible to influence the microphone output. Tightening this ring .tends to lower the response below 1000 cycles with respect to the higher frequencies. Adjustment of this retaining ring is the last step in finally determining the desired response for the microphone.

rI`he frequency response shown in FIGURE 7 achieved by a microphone having the above enumerated GQ11811116.-

lavalier microphone near the body of the user.

While a preferred exemplary embodiment of the present invention has been described in detail above, it -will be understood that modifications and variations may be effected therein without departing from the spirit and scope of the novel concepts of the present invention as defined by the following claims.

I claim as my invention:

`l. In a small compact microphone of the dynamic type 'having a movable voice coil mounted on a diaphragm substantially closing, and resonating with, a rear cavity, all in a casing having an open front, means, including an outer grille over the open front of said casing and said diaphragm and a grille-like bafile disk between said outer grille and said diaphragm, said baffle disc having perforations therethrough of 4a size to selectively increase the high end frequency response of the frequency response curve of said microphone.

2. In a `dynamic microphone of the diaphragm-voice coil type, the improvement to better the reproduction of tonal quality comprising means forming a cavity positioned to the rear of, .and communicating with the back of, said diaphragm and a vent tube connecting said cavity to the front sound field adjacent to said diaphragm by an annular opening around said diaphragm sonic damping means in said annular opening, means other- Wise substantially sealing said cavity, said cavity and said vent tube together being resonant to increase the lower end frequency response of said microphone.

3. A dynamic microphone comprising, a generally cylindrical outer case having a fron-t opening, said casing enclosing inner and outer sleeve members, a back cavity at least partly in said sleeve members, said vent passage opening at one end to said back cavity inside said case member to be resonant therewith at low frequencies and opening at the other end to the outside front of said case, a permanent magnet assembly in said sleeve members having a central pole and a surrounding annular pole radially spaced therefrom to define an annular'air gap, a ring of fibrous material between said outer annular plate and a retaining ring adjustable along said inner pole, a diaphragm mounted voice coil free to move said air gap, said diaphragm being operatively connected to said annular outer pole, said retaining ring being axially adjustable to variably compress said fibrous material to change its sonic resistance and thus adjust the frequency response of said microphone.

4. Apparatus as in claim 3 wherein fibrous material is lightly packed in at least a portion of said resonant system formed by said back cavity and said vent tube to smooth out the frequency response curve of said microphone.

5. A microphone of the diaphragm-voice coil type comprising a diaphragm, a magnet having an axially ex- ,tending central pole piece means forming a vented, resonating cavity positioned to the rear of said diaphragm, a restricted and transversely extending passage means connecting the back of said diaphragm to said vented cavity, said cavity being resonant with said diaphragm to increase the lower frequency response thereof, sonic friction producing means to control the intermediate frequency response of said microphone comprising a layer of sonic friction producing fibrous material in, and extending across, said passage means, and means `to variably tune said intermediate frequency response of said microphone comprising a wall means adjustably movable axially along said elongated central pole piece means to variably compress said layer of fibrous material, said movable wall means defining one side of said transversely extending passage means.

6. A microphone of the `diaphragm-voice coil type cornprising a diaphragm, an elongated, small diameter vent tube means opening to directly receive low frequencyV sound separately from said diaphragm, means at the rear of said diaphragm forming a cavity vented by and resonant with said Vent tube means and communicating with a smaller volume yat the back of said diaphragm by a restricted passage means to increase the lower frequency response of said diaphragm, means to control primarily .the intermediate `frequency response of said microphone comprising sonic friction producing, fibrous material in said restricted passage means 4and an adjustably movable wall means variably defining said restricted passage and engaging and variably compressing said fibrous material.

7. In a microphone of the dynamic diaphragm-voice coil type yhaving a diaphragm mounted voice coil movable in the air gap of its permanent magnet mounted in back `of said diaphragm, Ithe improvement to better the tonal quality and the response curve of said microphone comprising a grille-like restricting member perforated to increase the upper end frequency response of said microphone and mounted outwardly from the front of said diaphragm, means forming an enclosed cavity in back of said diaphragm, and means forming a long, small crosssectional area vent tube extending around, and connecting sa-id cavity to the periphery of the front of, said microphone, said cavity being resonant with said vent tube to increase the lower end frequency response of said microphone.

8. A dynamic microphone comprising a permanent magnet unit having a central pole and an outer annular pole portion to define an annular air gap therebetween, aretaining ring adjustable aolng said cen-tral pole, a ring of fibrous material on said central pole adjustable clamped between said annular pole portion and said retaining ring, a diaphragm secured relative to said annular pole portion, a voice coil mounted on said diaphragm forl axial movement in said air gap, means :to control the higher frequency response of said -microphone including a perforated grill-like member in front of said diaphragm, an outer grill member protectively covering said perforated member and said diaphragm, said magnet-diaphragm assembly being mounted in a case having an opening in the front thereof, an enclosed cavity in said case and in back of said diaphragm, means forming a long vent tube passage helically surrounding said magnet-diaphragm assembly in said case, said vent passage opening at one end to said enclosed cavity and opening iat its other end to the outside of said case, said cavity being resonant with its vent passage at lower frequencies to increase the lower end response of lsaid microphone, said retaining ring being adjustable in position to adjust and tune 'the intermediate frequency response of said microphone.

9. A dynamic microphone comprising, an outer case having an opening at the front thereof, an outer sleeve member positioned within said case near said front opening, an inner sleeve member supported within said outer sleeve member, one of said sleeve members having a helical groove therein defining with said other sleeve member a long vent passage of small cross-sectional area, a permanent magnet unit having an air gap and mounted within said inner sleeve member, a diaphragm mounted voice coil free to move in said air gap, means to support said diaphragm in front of said sleeve members, a cavity in back of and substantially enclosing said diaphragm, said vent passage opening at one end to said enclosed cavity and at its other end to the front portion of said case, said cavity being resonant with said vent passage -to increase the lower end frequency response of said microphone. i

'10. A dynamic microphone comprising a permanent magnet assembly having a central pole and a surrounding outer annular pole portion spaced therefrom to define an annular air gap therebetween, a retaining ring threadedly received on said central pole, a ring of fibrous material on said central pole between said adjustable ring and said annular pole portion to dene an adjustable sonic friction passage, adiaphragrn secured :relative to said outer pole portion, a voice coil mounted on said diaphragm for axial movement in said air gap, an inner grill-like member perforated to increase the higher frequency response of said microphone and mounted in front of said diaphragm, an outer grill member protectively covering said perforated member and said diaphragm, said maginet-diaphragm assembly being mounted in a case having an topening in the front thereof, a cavity in said case and in back of, and substantially close by, said diaphragm, means forming a vent passage helically surrounding said magnet-diaphragm assembly in said case, said vent passage opening :at one end to said enclosed cavity and opening at the other end thereof to said `opening in the front of said case, said cavity being resonant with its vent plassage at lower frequencies to increase the lower end response of said microphone, said retaining ring being adjustable in position to adjust the intermediate frequency response of said microphone, and fibrous material lightly packed in at least a part of said resonant system formed by said vent tube and said enclosed cavity to smooth ont the frequency response thereof.

ll. A microphone comprising a diaphragm means forming a vented resonating cavity positioned to the rear of said diaphragm, passage means connecting the back of said diaphragm to said cavity, said cavity being resonant with said diaphragm to increase the frequency response of said microphone below approximately 200 c.p.s., said passage means including a chamber of smaller volume than said cavity positioned directly back of said dilaphragm, said chamber forming a resonating part of said cavity, means to better the intermediate frequency response of said microphone below approximately 1,000

cps. comprising sonic friction producing, porous mate.

r-ial in said passage means between said chamber and said cavity, means to better the tone or quality of said microphone and increase its frequency response above approximately 5,000 c.p.s. comprising baffle means positioned forwardly of the front of said diaphragm.

12. A microphone comprising a sound vibrated diaphragm having its front exposed to the front sound field, means forming a resonating cavity positioned to the rear of said diaphragm, passage means connecting the back of said diaphragm to said cavity, said cavity being [resonant with said diaphragm at a frequency of approximately 300 c.p.s. and means forming an elongated passage venting said cavity to outside of said microphone through sonic damping means, said elongated passage having `a small cross-sectional area to attenuate high sonic frequencies and having a length to resonate with said cavity and said diaphragm at approximately t c.p.s.

13. In a dynamic microphone of the compact small iavalier-type having a diaphragm mounted voice coil free to move in the air gap of a permanent mag-net unit posiyti'oned in back of said diaphragm, the improvement comprising, an enclosed cavity positioned to the rear of, and communicating with the back of, said diaphragm, cylindrical means forming a long and small cross-sectional area vent tube in a helix, said cylindrical means being positioned around said magnet, an inlet to said vent tube positioned at a front peripheral edge of said microphone and adjacent said diaphragm, an outlet from said vent tube being in open communication with said cavity, said cavity being otherwise lsubstantially sealed, said cavity and said vent tube being resonant to increase the lower end frequency response of said microphone.

References Cited in the le of this patent UNITED STATES PATENTS 1,847,702 Thuras Mar. 1, 1932 1,964,606 rfhuras June 26, 1934 2,401,328 Black June 4, 1946 2,847,326 Muller Aug. l2, 1958 2,848,561 Gorke Aug. 19, 1958 2,862,070 Bonnafous Nov. 25, 1958 2,865,464 Gorike Dec. 23, 1958 2,939,922 Gorike June 7, 1960 FORETGN PATENTS 873,259 Ger-many Apr. 13, 1953 183,462 Austria Oct. l0, 1955 1,014,595 Germany Aug. 29, 1957

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3223782A (en) * 1961-06-19 1965-12-14 Akg Akustische Kino Geraete Directional microphone with distance control
US3258543A (en) * 1962-10-01 1966-06-28 Electro Voice Dynamic microphone
US3573395A (en) * 1968-07-10 1971-04-06 Henry B Whitmore Fireproof electrical isolation speaker
US3836724A (en) * 1971-12-27 1974-09-17 Chuo Denshi Kogyo Co Ltd Four channel headphone
US3999020A (en) * 1975-10-29 1976-12-21 Koss Corporation Transducer with variable frequency response
US5706359A (en) * 1997-01-13 1998-01-06 Chang; Ching-Lu Handheld microphone with a shockmount system

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1847702A (en) * 1931-05-02 1932-03-01 Bell Telephone Labor Inc Sound translating device
US1964606A (en) * 1932-04-12 1934-06-26 Bell Telephone Labor Inc Acoustic device
US2401328A (en) * 1943-01-16 1946-06-04 Bell Telephone Labor Inc Sound translating device
DE873259C (en) * 1943-08-29 1953-04-13 Lorenz C Ag Moving coil microphone with a influenced by a perforated disc air cushion
AT183462B *
DE1014595B (en) * 1955-02-15 1957-08-29 Lab Wennebostel directional microphone
US2847326A (en) * 1952-03-13 1958-08-12 Philips Corp Microphone comprising a magnet system
US2848561A (en) * 1953-06-02 1958-08-19 Akg Akustische Kino Geraete Dynamic microphone
US2862070A (en) * 1953-07-10 1958-11-25 App Et D Expl Des Ets Microphone
US2865464A (en) * 1954-08-07 1958-12-23 Gorike Rudolf Unidirectional dynamic microphone
US2939922A (en) * 1955-05-26 1960-06-07 Gorike Rudolf Directional microphone having a low susceptibility to shock and wind

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT183462B *
US1847702A (en) * 1931-05-02 1932-03-01 Bell Telephone Labor Inc Sound translating device
US1964606A (en) * 1932-04-12 1934-06-26 Bell Telephone Labor Inc Acoustic device
US2401328A (en) * 1943-01-16 1946-06-04 Bell Telephone Labor Inc Sound translating device
DE873259C (en) * 1943-08-29 1953-04-13 Lorenz C Ag Moving coil microphone with a influenced by a perforated disc air cushion
US2847326A (en) * 1952-03-13 1958-08-12 Philips Corp Microphone comprising a magnet system
US2848561A (en) * 1953-06-02 1958-08-19 Akg Akustische Kino Geraete Dynamic microphone
US2862070A (en) * 1953-07-10 1958-11-25 App Et D Expl Des Ets Microphone
US2865464A (en) * 1954-08-07 1958-12-23 Gorike Rudolf Unidirectional dynamic microphone
DE1014595B (en) * 1955-02-15 1957-08-29 Lab Wennebostel directional microphone
US2939922A (en) * 1955-05-26 1960-06-07 Gorike Rudolf Directional microphone having a low susceptibility to shock and wind

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3223782A (en) * 1961-06-19 1965-12-14 Akg Akustische Kino Geraete Directional microphone with distance control
US3258543A (en) * 1962-10-01 1966-06-28 Electro Voice Dynamic microphone
US3573395A (en) * 1968-07-10 1971-04-06 Henry B Whitmore Fireproof electrical isolation speaker
US3836724A (en) * 1971-12-27 1974-09-17 Chuo Denshi Kogyo Co Ltd Four channel headphone
US3999020A (en) * 1975-10-29 1976-12-21 Koss Corporation Transducer with variable frequency response
US5706359A (en) * 1997-01-13 1998-01-06 Chang; Ching-Lu Handheld microphone with a shockmount system

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