US3536862A - Microphone having a variable unidirectional characteristic - Google Patents

Microphone having a variable unidirectional characteristic Download PDF

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Publication number
US3536862A
US3536862A US659445A US3536862DA US3536862A US 3536862 A US3536862 A US 3536862A US 659445 A US659445 A US 659445A US 3536862D A US3536862D A US 3536862DA US 3536862 A US3536862 A US 3536862A
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Prior art keywords
microphone
characteristic
sound
deflecting member
bidirectional
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Expired - Lifetime
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US659445A
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English (en)
Inventor
Bernhard Weingartner
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AKG Acoustics GmbH
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AKG Akustische und Kino Geraete GmbH
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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
    • 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

  • a microphone having a cardioid directional characteristic when the sound detour through sound inlet openings communicating with forward and rear diaphragm faces, as measured on the outside of the microphone, has a predetermined length, is provided with a deflecting member mounted on the outside of the microphone between the sound inlet openings and adapted selectively to modify the length of the sound detour.
  • microphones which have an omnidirectional (spherical) characteristic there are known microphones which have an omnidirectional (spherical) characteristic, microphones which have a unidirectional (cardioid) characteristic and microphones which have a bidirectional (figure eight-shaped) characteristic.
  • the optimum characteristic for any particular application will depend on the conditions of use. Unidirectional microphones are preferable in most cases. The generation of a unidirectional characteristic can be explained most conveniently by reference to the principle of superposition.
  • a microphone having an omnidirectional characteristic and a microphone having a bidirectional characteristic are superposed, for example in a suitable electric circuit, the resulting system will have a unidirectional characteristic. If the contributions of the two microphones are the same (50% omnidirectional charact ristic and 50% bidirectional characteristic) an ideal cardioid directional characteristic will be obtained. If the bidirectional contribution is 75% and the omnidirectional contribution is 25%, a hypercardioid characteristic will be obtained and, a ratio of 63% bidirectional characteristic to 37% Omnidirectional characteristic results in a supercardioid characteristic.
  • each of these three unidirectional characteristics has its special advantages.
  • the pure cardioid characteristic results in a wide useful sound receiving angle, and in a good supression of direct sound which is incident from the rear (180).
  • the hypercardioid characteristic results in a cancelling at an angle 11 of about 110, and in the optimum suppression of diffused sound (reverberation). On the other hand, it results in a narrower receiving angle and a reduced suppression of sound incident fro-m the rear.
  • the supercardioid characteristic is a compromise of the two characteristics just discussed.
  • the acoustic elements of the pressure-responsive system having an omnidirectional characteristic, comprise a space which is closed from the Patented Oct. 27, 1970 ice outside air and connected by a frictional resistance to a relatively shallow air chamber behind the diaphragm.
  • the acoustic elements of the bidirectional system consist essentially of a suitably sized opening leading from the air chamber into the free rear sound field.
  • This invention relates to microphones having a pure cardioid characteristic and, more particularly, to such a microphone which can be converted ina simple manner into one having either a supercardiod characteristic or a hypercardioid characteristic.
  • a microphone having a pure cardioid characteristic, or equal omnidirectional and bidirectional contributions is provided with means whereby the sound detour is variable, the variation being effected by the provision of deflecting member in the form of a disk or sleeve on the exterior or outside of the microphone.
  • the deflecting member is in the form of a frustum of a cone. The deflecting member is located between the sound inlet opening, communicating with the forward face of the diaphragm, and the sound inlet opening communicating with the rear face of the diaphragm.
  • the deflecting member can be made detachable, adjustable in size, adjustable in shape, or to have any tWo or more of these characteristics.
  • the deflecting member may be formed with openings, apertures, slots or the like, which can be selectively closed by suitable mechanisms, the size of the openings or the like being preferably infinitely adjustable, in the manner of a variable orifice.
  • An object of the invention is to provide a microphone having a pure cardioid characteristic with means whereby the characteristic may be changed into a supercardioid characteristic or a hypercardioid characteristic, selectively.
  • Another object of the invention is to provide such a microphone including means for varying the sound detour between the sound inlet opening communicating with the forward face of the diaphragm and the sound inlet opening communicating with the rear face of the diaphragm.
  • a further object of the invention is to provide such a microphone in which such means comprises a deflecting member in the form of a disk or sleeve and mounted on the exterior or outside of the microphone.
  • Still another object of the invention is to provide such a deflecting member in the form of a frustum of a cone.
  • a further object of the invention is to provide such a member which is detachable.
  • Anotherobject of the invention is to provide such a deflecting member which'is adjustable in size or shape or both.
  • Another object of the invention is to provide such a deflecting member with openings or other forms of apertures Whose areas are preferably infinitely adjustable or variable by suitable mechanisms.
  • FIGS. 1, 2 and 3 are graphical representations of, respectively, an ideal cardioid directional characteristic, a hypercardioid directional characteristic and a supercardioid directional characteristic;
  • FIG. 4 is a sectional view of a microphone embodying the invention and illustrating the basic functioning of the deflecting member
  • FIG. 5 is a view, similar to FIG. 4, illustrating the deflecting member as formed with apertures therethrough;
  • FIG. 6 is a top plan view of FIG. 5;
  • FIG. 7 is an elevation view, partly in section.
  • FIGS. 1, 2 and 3 if the contribution of two microphones are the same, that is, 50% omnidirectional characteristic and 50% bidirectional characteristic, an ideal cardioid directional characteristic will be obtained as shown in FIG. 1. If the bidirectional contribution is 75% and the omnidirectional contribution is 25%, a hypercardioid directional characteristic will be obtained as shown in FIG. 2. If the bidirectional contribution is 6 3% and the omnidirectional contribution is 37%, a supercardioid characteristic will be obtained as shown in FIG. 3.
  • a capsule 1 of a dynamic microphone is illustrated as having a forward sound inlet 2 and a rear sound inlet 3.
  • a diaphragm 4 is illustrated in broken lines, and a pressure chamber 5 communicates with the rear of the capsule.
  • the sound detour d representing the external distance between the forward sound inlet 2 and the rear sound inlet 3, determines the magnitude of the actuating pressure difference, and consequently determines the bidirectional contribution.
  • the acoustic elements of the microphone system are so dimensioned that sound detour d results in a cardioid directional characteristic.
  • the microphone When a deflecting disk 6 is applied to the microphone, in accordance with the invention, the sound detour between the forward sound inlet 2 and the rear sound inlet 3 is increased to (1 As a result, the pressure difference and the bidirectional contribution will also increase so that the microphone system, having a cardioid characteristic, is converted by deflecting disk 6 into a microphone having a predominating bidirectional contribution. More particularly, the microphone is converted into one having a supercardioid or hypercardioid characteristic, depending on the size of the disk. To avoid irregularities in the frequency response due to the dynamic pressure eifect or due to diffraction effects of disk 6, the latter is preferably frusto-conical in form.
  • the deflecting member 6 is formed with openings 7 whose area is infinitely variable between a fully opened condition and a fully closed condition.
  • Disk 6 is preferably formed of plastic composition material.
  • a closing ring 8 is rotatably mounted in a groove 9 of disk 6', and preferably comprises punched sheet metal. Closing ring 8 is rotatable by adjusting lever '10, and has openings 11, corresponding to opening 7, which enable an infinitely variable opening and closing of openings 7.
  • the arrangement shown in FIGS. 5 and 6 is capable of providing three different sound detours and three different bidirectional contributions, namely d without the deflecting disk d with the deflecting disk having the openings 7 closed and d with the deflecting disk having the openings 7 open.
  • the detours are dimensioned so that al results in a cardioid characteristic, d in a hypercardioid characteristic and d in a supercardioid characteristic.
  • FIG. 7 A practical form of microphone embodying the invention is illustrated in FIG. 7.
  • microphone capsule 1 is incorporated in a housing 12 provided with a cap 13. Sound enters in front through protective screen 14 and enters at the rear through slots 15 in cap 13. Electrical connections are established by cable 16, and the deflecting disk 6, in accordance with the invention, is adapted to be fitted to cap 13.
  • the deflecting disk may be provided in different shapes, such as circular, elliptical, or polygonal. Type references and the name of the manufacturer may be provided on the deflecting member 6, which preferably is formed of plastic composition material.
  • deflecting member 6 may be used as a foot or the like for supporting the microphone of the table.
  • the deflecting member may be flatter than shown in the drawings or may more closely resemble a sleeve. While its contour is preferably circular, elliptical or polygonal, alternatively the deflecting disk may have a star-shaped contour or the like. Also, the size of the deflecting member may be made variable, in the manner of an iris diaphragm such as used in photography, but arranged to vary the outside diameter of the deflecting member.
  • a microphone having a variable unidirectional characteristic, comprising, in combination, a capsule containing electro-acoustic transducer means having forward and rear diaphragm faces; means defining forward and rear sound inlet openings communicating with said forward and rear diaphragm faces, respectively; a sound detour representing the external distance between said inlet openings as measured on the outside of said microphone, said microphone having a cardioid directional characteristic in response to sound waves entering through said sound inlet openings when said sound detour has a predetermined length; and a sound path deflecting member mountable on the external periphery of said capsule between said sound inlet openings to modify selectively the length of said sound detour to obtain differently defined unilateral directional characteristics for said microphone.
  • a microphone as claimed in claim 1, in which the size of said deflecting member is selectable to select the desired length of said sound detour.
  • a microphone as claimed in claim 1, in which said transducer means comprises a single diaphragm having said forward and rear faces.
  • a microphone as claimed in claim 1, in which said deflecting member is disengageably mounted on said microphone; said sound detour having said predetermined length When said deflecting member is removed from said microphone, and having a length greater than said predetermined length when said deflecting member is mounted on said microphone.
  • a microphone as claimed in claim 1, in which the external periphery of said deflecting member is in the form of a closed plane geometric figure, said deflecting member forming a support for said microphone on a base.
  • a microphone as claimed in claim 1, in which said deflecting member has a form of a flat truncated cone.
  • a microphone as claimed in claim 1, in which said deflecting member has a frictional fit on said microphone.
  • a microphone as claimed in claim 1, in which said deflecting member is formed with sound passage apertures therethrough.
  • a microphone as claimed in claim 8, in which said deflecting member includes adjusting means selectively operable to vary the areas of said apertures to vary the length of said sound detour.
  • a microphone as claimed in claim 9, in which said adjusting means is continuously adjustable.
  • a microphone as claimed in claim 5, in which said deflecting member has an elliptical external periphery.
  • a microphone as claimed in claim 5, in which said deflecting member has a polygonal external periphery.
  • a microphone as claimed in claim 5, in which said deflecting member includes a ring of elastic material extending around its external periphery and projecting at least partly from said external periphery.
  • a microphone as claimed in claim 1, in which said deflecting member is substantially disk-shaped.

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  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
  • Details Of Audible-Bandwidth Transducers (AREA)
US659445A 1966-08-19 1967-08-09 Microphone having a variable unidirectional characteristic Expired - Lifetime US3536862A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AT793066A AT277339B (de) 1966-08-19 1966-08-19 Mikrophon mit Richtcharakteristik und einer Einrichtung zur Veränderung dieser Richtcharakteristik

Publications (1)

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US3536862A true US3536862A (en) 1970-10-27

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US (1) US3536862A (de)
AT (1) AT277339B (de)
DE (1) DE1537573A1 (de)
GB (1) GB1181868A (de)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2194101A1 (de) * 1972-07-21 1974-02-22 Industrial Research Prod Inc
US3921016A (en) * 1973-12-12 1975-11-18 Proctor & Assoc Co Sonic signal generator and housing
US3995124A (en) * 1974-09-25 1976-11-30 Saad Zaghloul Mohamed Gabr Noise cancelling microphone
US4449236A (en) * 1982-04-08 1984-05-15 Walker Equipment Corporation Anti-side tone transmitter
US4528426A (en) * 1983-11-23 1985-07-09 Northern Telecom Limited Directional microphone assembly
US4584702A (en) * 1983-12-19 1986-04-22 Walker Equipment Corporation Noise cancelling telephone transmitter insertable in telephone handset receptacle
US4862507A (en) * 1987-01-16 1989-08-29 Shure Brothers, Inc. Microphone acoustical polar pattern converter
US5115470A (en) * 1990-04-11 1992-05-19 Sutheim Peter E Sound reinforcement system
US5627901A (en) * 1993-06-23 1997-05-06 Apple Computer, Inc. Directional microphone for computer visual display monitor and method for construction
US5692060A (en) * 1995-05-01 1997-11-25 Knowles Electronics, Inc. Unidirectional microphone
US20100032233A1 (en) * 2008-08-07 2010-02-11 Moore Dana A Wide frequency range horn with modular method for reducing diffraction effects
US8948434B2 (en) 2013-06-24 2015-02-03 Michael James Godfrey Microphone

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2787671A (en) * 1952-10-06 1957-04-02 Schall Technik Dr Ing Karl Sch Microphone arrangement

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2787671A (en) * 1952-10-06 1957-04-02 Schall Technik Dr Ing Karl Sch Microphone arrangement

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2194101A1 (de) * 1972-07-21 1974-02-22 Industrial Research Prod Inc
US3921016A (en) * 1973-12-12 1975-11-18 Proctor & Assoc Co Sonic signal generator and housing
US3995124A (en) * 1974-09-25 1976-11-30 Saad Zaghloul Mohamed Gabr Noise cancelling microphone
US4449236A (en) * 1982-04-08 1984-05-15 Walker Equipment Corporation Anti-side tone transmitter
US4528426A (en) * 1983-11-23 1985-07-09 Northern Telecom Limited Directional microphone assembly
US4584702A (en) * 1983-12-19 1986-04-22 Walker Equipment Corporation Noise cancelling telephone transmitter insertable in telephone handset receptacle
US4862507A (en) * 1987-01-16 1989-08-29 Shure Brothers, Inc. Microphone acoustical polar pattern converter
US5115470A (en) * 1990-04-11 1992-05-19 Sutheim Peter E Sound reinforcement system
US5627901A (en) * 1993-06-23 1997-05-06 Apple Computer, Inc. Directional microphone for computer visual display monitor and method for construction
US5692060A (en) * 1995-05-01 1997-11-25 Knowles Electronics, Inc. Unidirectional microphone
US20100032233A1 (en) * 2008-08-07 2010-02-11 Moore Dana A Wide frequency range horn with modular method for reducing diffraction effects
US7845462B2 (en) * 2008-08-07 2010-12-07 Moore Dana A Wide frequency range horn with modular method for reducing diffraction effects
US8948434B2 (en) 2013-06-24 2015-02-03 Michael James Godfrey Microphone

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Publication number Publication date
DE1537573A1 (de) 1969-09-18
GB1181868A (en) 1970-02-18
AT277339B (de) 1969-12-29

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