US3204031A - Moving-coil microphone arrangement - Google Patents

Moving-coil microphone arrangement Download PDF

Info

Publication number
US3204031A
US3204031A US134669A US13466961A US3204031A US 3204031 A US3204031 A US 3204031A US 134669 A US134669 A US 134669A US 13466961 A US13466961 A US 13466961A US 3204031 A US3204031 A US 3204031A
Authority
US
United States
Prior art keywords
frequency
microphones
microphone
diaphragm
acoustic
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
US134669A
Inventor
Gorike Rudolf
Schuster Karl
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.)
AKG Acoustics GmbH
Original Assignee
AKG Acoustics GmbH
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 AKG Acoustics GmbH filed Critical AKG Acoustics GmbH
Priority to US134669A priority Critical patent/US3204031A/en
Application granted granted Critical
Publication of US3204031A publication Critical patent/US3204031A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • H04R1/26Spatial arrangements of separate transducers responsive to two or more frequency ranges
    • H04R1/265Spatial arrangements of separate transducers responsive to two or more frequency ranges of microphones
    • 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
    • H04R1/32Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only
    • H04R1/34Arrangements 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
    • H04R1/38Arrangements 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

Description

1965 R. GORIKE ETAL 3, 7
MQVING-COIL MICROPHONE ARRANGEMENT Filed Aug. 29, 1961 l MICROPHONE) MICROPHbfi Z I l x X I 6 T 14 Y i 1:
| FILTER Fi l-T ER 21 AMPLIFIEE RUDOLF G'C'DRIKEY KARL SCHUSTER INVENTORS.
AGENT United States Patent 3,204,031 MOVING-C011. MTCROPHUNE ARRANGEMENT Rudolf fiiirilre and Karl 'Schuster, both of Vienna, Austria, assignors to Akustische U. Kino-Gerate Geseilschaft m.b;H., Vienna, Austria, a firm Filed Aug. 29, 1961, Ser.=N0. 134,669 11 Claims. (Cl. 179-1) The necessity of causing sound waves to act on a diaphragm from both sides to achieve a directional pattern with moving-coil microphones involves difiiculties if a wide frequency range is to be utilized. This is due to the fact that the requirement for mass retardation of the vibrating system (diaphragm) necessitates a sufiiciently compliant mounting of the diaphragm (low restoring force). It has been found in practice that this results in an unsteady frequency response in the higher frequency range.
To provide dynamic microphone arrangements having a unidirectional pattern, two independent individual microphones, namely, a moving-coil pressure transmitter and a ribbon microphone, have been arranged one beside the other and electrically connected together. This resulted in a transformation of the omnidirectional and bidirectional patterns into a unidirectional pattern.
As contrasted therewith, the invention relates to a moving-coil microphone arrangement in which at least two mechanically independent individual microphones are arranged close to each other electrically connected together, and the individual microphones having substantially equaldirectional patterns and optimum frequency responses in different frequency ranges.
It is known to allocate different frequency ranges to two or more individual loudspeakers. This allocation has the purpose to obtain the necessary sound volume in the lower frequency range by the use of a sufiiciently large diaphragm area and to obtain a propagation of sound at high frequencies in a wide angle by the use of a stiff diaphragm which is as small as possible.
According to the invention, the diaphragms are of substantially identical surface area but differ substantially in their mounting and the acoustic elements coupled to the diaphragm.
The low-frequency diaphragm has suitably coupled to its rear side the acoustic analog of a resistive-reactive transit-time system, specifically an LR system, whereas the acoustic analog of another resistive-reactive transittime system, i.e., an RC system, is suitably coupled to the rear side of the high-frequency diaphragm. The analog of an LR system comprises an acoustic mass (L) in a duct which opens into a shallow air chamber behind the diaphragm, this air chamber having connected to it an acoustic frictional resistance (R) which opens into a sufficiently large chamber shut off from the external sound field. The analog of an RC system comprises an air chamber (C) and an acoustic frictional resistance (R), both of which are coupled to the rear side of the diaphragm, the resistance leading to the external sound field. Both systems are known to provide the required phase shift and are referred to as transit-time systems. The high-frequency diaphragm may also have the analog of an LR system coupled to it. Both RC and LR analog systems may be coupled to one and the same diaphragm.
The point of division between the frequency ranges is suitably so selected that the high-frequency microphone begins to predominate where the frequency curve of the low-frequency microphone begins to become unsteady. In practice, this point of division will lie between 300 and 1000 cycles, depending on the design of the individual microphones.
The diaphragm of the low-frequency microphone may be gripped under such stress as to resonate between 120 I ice and 400 cycles. Owing to the mass loading of the diaphragm by the acoustic mass L of the associated transit tirne system, the natural frequency of the overall vibratory system is shifted in known manner toward the lower end of the acoustic band (e.g., 40 cycles). [To increase the pressure gradient, one or more tubes 10-30 'centime ters long may be coupled to the diaphragm in known manner. In this case to constitute the analog of the' inductive branch (L) of the system in thefrequency re-' sponse are not to be expected up to 500 to 1000. cycles.
The high-frequency microphone may also be optimally designed and have a relatively stiffly gripped diaphragm so as to exhibit a relatively elevated inherent resonant frequency (400800 cycles). An acoustic transit-time system may be provided on the rear side of the diaphragm (RC or LRsystem) to ensure a very smooth frequency response in the higher frequency range and a constant twoway damping.
The two microphones are advantageously arranged so that the low-frequency microphone lies behind the highfrequency microphone. A disturbing influence, due to mutual interference, upon the frequency response and directional pattern in the overlap range is not to be expected because the sound wave length in that range is a multiple of the selected distance between the microphones which, therefore, receive the incident acoustic waves at these (and lower) frequencies nearly in phase.
The electrical circuitry connecting the microphones may include electrical filters. The microphone'outputs may be directly connected to a common amplifying channel, or individual amplifying channels may be provided which have outputs that are connected together. Such variations are basically lcnown per se.
it will be understood that any desired frequency range can be divided according to the invention into adjoining subranges or bands associated with more than two'microphones. Nor is the invention restricted to directional microphones; it is also applicable to pressure transmitters having an omnidirectional pattern.
An embodiment of the invention is diagrammatically illustrated in the accompanying drawing, in which:
FIG. 1 is a block diagram showing the microphone arrangement; Y
FIG. 2 is a diagrammatic representation of a high-frequency microphone provided with an analog RC system; and
FIG. 3 'is a diagrammatic representation of a low-frequency microphone provided with an analog LR system.
With reference to FIG. 1, a high-frequency microphone 1 and a low-frequency microphone 2 are secured in a common housing 3 and electrically connected together in series, and to an amplifier 4, via respective filters 21, 22 designed to suppress undesirable frequencies.
In FIG. 2, which illustrates a representative embodiment of high-frequency microphone 1, a shallow air chamber 5 is defined by a diaphragm 6 and a rear wall 12 comprising three acoustic frictional resistances (R) designated 7, 8 and 9. The resistances 7 and 9 lead to the outside air. The resistance 8 leads to a closed chamber 10 confined by a pot-shaped housing member 11 and constituting an acoustic capacitance (C).
In FIG. 3, showing a representative embodiment of low-frequency microphone 2, a shallow air chamber 13 is defined by a diaphragm 14 and a rear wall 15 comprising an acoustic frictional resistance (R), designated 16, leading to a closed chamber 17 confined by a pot-shaped housing member 18. Chamber 17 contains a mass of air, larger than that present within chamber 10, which adjoins the rear side of the frictional resistance 16 and is otherwise separated from the outside air. Radially outwardly of the chamber 17, tubes 19, which contain air columns acting as inertances or acoustic inductance equiv- 3 alents (L), open into the air chamber 13 at the rear wall 15. At their other end, these tubes 19 open into the atmosphere. The air cushions 5 and 13 can, of course, also be considered as acoustic capacitances (C).
As will be seen from FIGS. 1-3, microphones 1 and 2 have their diaphragms 6, 14 facing in the same direction and centered on a common axis, these diaphragms spanning the open front ends of the microphone housings (Whose rear ends are partly open into the atmosphere at 7 and 19). The diaphragm 14 of the low-frequency microphone 2 faces the rear of the high-frequency microphone 1, the two microphones being separated by a distance which, as previously pointed out, should be a fraction of the acoustic-Wave length in the overlapping region of their respective frequency bands. Since the axial length of microphone 1 is less than that of microphone 2, as seen in FIGS. 2 and 3, this arrangement affords maximum flexibility in. selecting the spacing of the two microphones from each other.
The diaphragms 6 and 14 are of the moving-coil type, yet their conventional coils and associated circuitry have not been illustrated.
What is claimed is:
1. A microphone arrangement comprising at least two mechanically independent directional moving-coil microphones separated from each other by a fraction of a wavelength at a predetermined acoustic frequency, each of said microphones having a housing with an open front end and a partly open rear end, each of said microphones further having a vibratory system in said housing including an exposed diaphragm spanning said front end and an air mass adjacent the rear surface of said diaphragm, said diaphragms facing in the same direction, the vibratory system of one of said microphones having a natural frequency above said predetermined frequency, the vibratory system of the other of said microphones having a natural frequency below said predetermined frequency, and a common output circuit for said microphones.
2. A microphone arrangement as defined in claim 1 wherein the housing of said one microphone has at least one rear aperture relatively close to its front end, the housing of said other microphone having at least one rear aperture relatively remote from its front end.
3. A microphone arrangement;'as- -defined in claim 2 wherein said rear aperture of said one microphone is provided with frictional acoustic resistance means, the housing of said other microphone forming at least one rearwardly directed elongated tube terminating at said rear aperture thereof.
4. A microphone arrangement as defined in claim 3 wherein the diaphragms of said microphones are centered on a common axis, the diaphragm of said other microphone facing the rear of the housing of said one microphone.
5. A microphone arrangement as defined in claim 1 wherein said common output circuit includes filters individual to said microphones.
6. A microphone arrangement as defined in claim 1 wherein said predetermined acoustic frequency lies in the range of 300 to 1000 cycles per second.
7. A microphone arrangement comprising a high-frequency and a low-frequency directional microphone of the moving-coil type facing in the same direction while being separated from each other by a fraction of a wavelength at a predetermined acoustic frequency, said highfrequency microphone including a first housing With an open front end spanned by a first diaphragm and a first transmit-time system constituted by a rear portion of said first housing behind said first diaphragm, said rear portion having at least one restricted rear aperture relatively close to said first diaphragm, the combination of said first transit-time system and said first diaphragm having a natural frequency above said predetermined acoustic frequency, said low-frequency microphone including a second housing with an open front end spanned by a second diaphragm and a second transit-time system constituted by a rear portion of said second housing behind said second diaphragm, each of said second systems being the acoustic analog of a predominantly resistive-reactive electric circuit, the last-mentioned rear portion having at least one restricted rear aperture relatively remote from said second diaphragm, the combination of said second transit-time system and said second diaphragm having a natural frequency below said predetermined acoustic frequency; and a common output circuit for said microphones.
8. A microphone arrangement as defined in claim 7 wherein said first diaphragm is stressed to an inherent natural frequency in a range of 400 to 800 cycles per second, said second diaphragm being stressed to an inherent natural frequency lying in a range of 120 to 400 cycles per second.
9. A microphone arrangement as defined in claim 8 wherein the natural frequency of the combination of said second diaphragm and said second transit-time system is near the lower end of the acoustic band.
10. A microphone arrangement as defined in claim 7 wherein said first transit-time system is the acoustic analog of a predominantly resistive-capacitive electric circuit.
11. A microphone arrangement as defined in claim 7 wherein said second transit-time system is the acoustic analog of a predominantly resistive-inductive electric circuit.
References Cited by the Examiner UNITED STATES PATENTS 2,262,146 11/41 Massa 179-1 2,305,599 12/42 Bauer 179-1 2,702,318 2/55 Dvorsky 179111 FOREIGN PATENTS 884,516 7/53 Germany.
OTHER REFERENCES Friedman et al.: (A New Cardioid) Tele-Tech and Electronic Industries, October 1955; pages -72 and 129-433.
ROBERT H. ROSE, Primary Examiner.

Claims (1)

1. A MICROPHONE ARRANGEMENT COMPRISING AT LEAST TWO MECHINICALLY INDEPENDENT DIRECTIONAL MOVING-COIL MICROPHONES SEPARATES FROM EACH OTHER BY A FRACTION OF A WAVELENGTH AT A PREDETERMINED ACOUSTIC FREQUENCY, EACH OF SAID MICROPHONES HAVING A HOUSING WITH AN OPEN FRONT END AND A PARTLY OPEN REAR END, EACH OF SAID MICROPHONES FURTHER HAVING A VIBRATORY SYSTEM IN SAID HOUSING INCLUDING AN EXPOSED DIAPHRAGM SPANNING SAID FRONT END AND AN AIR MASS ADJACENT THE REAR SURFACE OF SAID DIAPHRAGM, SAID DIAPHRAGMS FACING IN THE SAME DIRECTION, THE VIBRATORY SYSTEM OF ONE OF SAID MICROPHONES HAVING A NATURAL FREQUENCY ABOVE SAID PREDETERMINED FREQUENCY, THE VIBRATORY SYSTEM OF THE OTHER OF SAID MICROPHONES HAVING A NATURAL FREQUENCY BELOW SAID PREDETERMINED FREQUENCY, AND A COMMON OUTPUT CIRCUIT FOR SAID MIRCOPHONES.
US134669A 1961-08-29 1961-08-29 Moving-coil microphone arrangement Expired - Lifetime US3204031A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US134669A US3204031A (en) 1961-08-29 1961-08-29 Moving-coil microphone arrangement

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US134669A US3204031A (en) 1961-08-29 1961-08-29 Moving-coil microphone arrangement

Publications (1)

Publication Number Publication Date
US3204031A true US3204031A (en) 1965-08-31

Family

ID=22464411

Family Applications (1)

Application Number Title Priority Date Filing Date
US134669A Expired - Lifetime US3204031A (en) 1961-08-29 1961-08-29 Moving-coil microphone arrangement

Country Status (1)

Country Link
US (1) US3204031A (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3403223A (en) * 1964-05-20 1968-09-24 Philips Nv Microphone combinations of the kind comprising a plurality of directional sound units
US3581012A (en) * 1967-07-13 1971-05-25 Sony Corp Unidirectional microphone
US4340787A (en) * 1979-03-22 1982-07-20 AKG Akustische u. Kino-Gerate Gesellschaft-mbH Electroacoustic transducer
US4646873A (en) * 1986-03-04 1987-03-03 Electro-Voice, Inc. Microphone and acoustic equalizer therefor
US4653606A (en) * 1985-03-22 1987-03-31 American Telephone And Telegraph Company Electroacoustic device with broad frequency range directional response
US5073946A (en) * 1986-09-19 1991-12-17 Matsushita Electric Industrial Co., Ltd. Thin speaker having an enclosure with an open portion and a closed portion
US5341420A (en) * 1990-09-06 1994-08-23 British Telecommunications Public Limited Company Noise-cancelling handset

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2262146A (en) * 1940-01-31 1941-11-11 Rca Corp Sound translating apparatus
US2305599A (en) * 1941-04-08 1942-12-22 S N Shure Conversion of wave motion into electrical energy
DE884516C (en) * 1940-12-09 1953-07-27 Siemens Ag Electrostatic microphone
US2702318A (en) * 1951-01-10 1955-02-15 Astatic Corp Unidirectional microphone

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2262146A (en) * 1940-01-31 1941-11-11 Rca Corp Sound translating apparatus
DE884516C (en) * 1940-12-09 1953-07-27 Siemens Ag Electrostatic microphone
US2305599A (en) * 1941-04-08 1942-12-22 S N Shure Conversion of wave motion into electrical energy
US2702318A (en) * 1951-01-10 1955-02-15 Astatic Corp Unidirectional microphone

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3403223A (en) * 1964-05-20 1968-09-24 Philips Nv Microphone combinations of the kind comprising a plurality of directional sound units
US3581012A (en) * 1967-07-13 1971-05-25 Sony Corp Unidirectional microphone
US4340787A (en) * 1979-03-22 1982-07-20 AKG Akustische u. Kino-Gerate Gesellschaft-mbH Electroacoustic transducer
US4653606A (en) * 1985-03-22 1987-03-31 American Telephone And Telegraph Company Electroacoustic device with broad frequency range directional response
US4646873A (en) * 1986-03-04 1987-03-03 Electro-Voice, Inc. Microphone and acoustic equalizer therefor
US5073946A (en) * 1986-09-19 1991-12-17 Matsushita Electric Industrial Co., Ltd. Thin speaker having an enclosure with an open portion and a closed portion
US5341420A (en) * 1990-09-06 1994-08-23 British Telecommunications Public Limited Company Noise-cancelling handset

Similar Documents

Publication Publication Date Title
US5025885A (en) Multiple chamber loudspeaker system
US5261006A (en) Loudspeaker system comprising a helmholtz resonator coupled to an acoustic tube
US3688864A (en) Infinite dynamic damping loudspeaker systems
US4160135A (en) Closed earphone construction
US9794682B2 (en) Electroacoustic transducer and acoustic resistor
JP3410206B2 (en) Speaker device
US4653606A (en) Electroacoustic device with broad frequency range directional response
US2689016A (en) Sound reproducing system
US2939922A (en) Directional microphone having a low susceptibility to shock and wind
JP2008219933A (en) Acoustic element and method for sound processing
DE112014002634T5 (en) Acoustic receiver with internal shielding
US5115473A (en) Transducer having two ducts
US3204031A (en) Moving-coil microphone arrangement
US4074070A (en) Supersonic signal linearizes loudspeaker operation
US2401328A (en) Sound translating device
US2773933A (en) Third order pressure gradient responsive microphone
US4340787A (en) Electroacoustic transducer
US3657490A (en) Tubular directional microphone
US2580439A (en) Directional acoustic system
US3403223A (en) Microphone combinations of the kind comprising a plurality of directional sound units
US2841648A (en) Sound producing device
US3053339A (en) Pipe microphone
US3115207A (en) Unidirectional microphone
US2745508A (en) Microphone support
CA2385582C (en) Multiple driver, resonantly-coupled loudspeaker