US3657490A - Tubular directional microphone - Google Patents

Tubular directional microphone Download PDF

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Publication number
US3657490A
US3657490A US15082A US3657490DA US3657490A US 3657490 A US3657490 A US 3657490A US 15082 A US15082 A US 15082A US 3657490D A US3657490D A US 3657490DA US 3657490 A US3657490 A US 3657490A
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United States
Prior art keywords
tube
set forth
directional microphone
impedance elements
capsule
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Expired - Lifetime
Application number
US15082A
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English (en)
Inventor
Robert Scheiber
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.)
RAIMUND HAUSER
Original Assignee
Vockenhuber Karl
Hauser Raimund
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Publication date
Application filed by Vockenhuber Karl, Hauser Raimund filed Critical Vockenhuber Karl
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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
    • H04R1/342—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 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
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/222—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only  for microphones

Definitions

  • At least one directional tube communicates with a sound transmitter capsule and is provided with acoustic impedance elements spaced along said tube and having predetermined cut-off frequencies, which increase in one direction along said tube, and predetermined natural frequencies, which decrease as the distance of the impedance elements of the capsule increases, whereby the effective length of said tube decreases as the frequency of sound is increased.
  • the spacing and natural frequencies of said impedance elements are selected so that the effective length of said tube is divided into two outer sections and an intermediate section.
  • Said two outer sections have a relatively low sensitivity and are arranged to subject sound received from said impedance elements in said outer sections to mutually opposite phase displacements amounting to approximately rr/Z.
  • Said intermediate section has a relatively high sensitivity and is arranged to subject sound received from said impedance elements in said intermediate section to zero phase displacement.
  • This invention relates to a tubular directional microphone which comprises sound inlet openings, which are spaced apart along the tube and provided with acoustic impedance elements comprising preferably damped spring-mass plug systems, the directivity being due to the interference between the waves entering the tube through the sound inlet openings and the cut-off frequencies increasing in one direction.
  • a tubular directional microphone When a tubular directional microphone is exposed to sound from a front source, the waves inside and outside the tube are substantially in phase and the sound energies entering through the several sound inlet openings are added. When the microphone is exposed to sound from a rear source, the waves inside and outside the tube are in phase opposition and an interference results which causes in part a complete extinction.
  • the directional characteristic of a tubular directional microphone depends highly on the ratio UK, where L is the length of the tube and A the wavelength of the sound. If the ratio L/k is less than one-fourth, the directional characteristic of the microphone will approach an omnidirectional characteristic whereas there is a pronounced directivity for treble frequencies. It has been attempted in some cases to improve the directivity of directional microphones by the use of longer tubes.
  • directional tubes having a length of several meters have been disclosed. Whereas such microphones have excellent directional characteristics, they can be used in practice only in exceptional cases.
  • the overall length of the microphone is decreased in that the directional tube is designed as an acoustic line which for frequencies having a wavelength in excess of the mechanical length of the tube have a transit time which increases as the frequency decreases.
  • the sound entered through a slot which extended throughout the length of the tube and which may vary in width.
  • the sound inlet slot is covered by a damping woven fabric, which acts as an acoustic resistance.
  • the phase displacement is due to the cooperation of the acoustic resistance of the covering on the slot and the acoustic line.
  • an increased phase displacement and a higher sensitivity are obtained only at the end portions of the tube.
  • the two known tubular directional microphones have the disadvantage that one of them has a relatively low directivity, whereas the other microphone has directional characteristics being still considerably dependent on frequency and has a large overall length.
  • the disadvantages of the known microphones are avoided in that the impedance elements are so tuned and arranged along the tubular directional microphone that the effective length of the tube is divided into two sections having a low sensitivity and effecting mutually opposite phase displacements of about 11/2 and a section, which is disposed between said two sections and has a high sensitivity and effects no phase displacement, and the effective tube length is decreased for increasing frequencies in that the impedance elements are tuned to lower frequencies as their distance from the microphone capsule increases.
  • the tubular directional microphone according to the invention has an excellent directivity, which is highly independent of frequency in a very large frequency range. This result is due to the desirable distribution of the phase displacement and sensitivity over the effective length of the tube and the reduction of said effective length in dependence on frequency.
  • the sound inlet passages which lead into the directional tube and constitute mass plugs are covered on the outside, in known manner, by an acoustic resistance consisting e.g. of woven fabric or felt.
  • the inlet passages serving as mass plugs have a length of a plurality of centimeters for bass frequencies.
  • the sound inlet passages consist preferably of non-straight acoustic lines.
  • the interference action occurring in a tubular directional microphone in combination with a pressure gradient action in order to enable the use of smaller overall lengths and/or to improve the directivity of the microphone.
  • the interference action is used only for treble frequencies whereas the pressure gradient action is used in the microphone for the bass frequencies.
  • the tubes of such directional microphones have a small overall length of about 50 centimeters but have the disadvantage that interfering signals at bass frequencies are not sufficiently damped owing to the low directivity of directional pressure gradient microphones having cardioid, supercardioid and bidirectional patterns, although such interfering signals at bass frequencies occur rather often.
  • At least one additional directional element is provided in known manner, which acts on the microphone capsule and is preferably similarly designed.
  • the arrangement may be such that one directional tube acts on one side of a microphone diaphragm and a second directional tube acts on the other side of the microphone diaphragm.
  • FIG. 1 is a side elevation showing a tubular directional microphone according to the invention
  • FIG. 2 is an enlarged longitudinal sectional view taken through the directional tube.
  • FIG. 3 is a sectional view taken on line III--III in FIG. 2.
  • FIGS. 4 and 5 are graphs illustrating the sensitivity distribution and the additional phase displacement along the tube length for a frequency of 200 cycles per second.
  • FIG. 6 illustrates diagrammatically the sensitivity distribution of a tubular directional pressure gradient microphone.
  • FIG. 7 is an exploded view showing a tubular directional pressure gradient microphone.
  • a directional tube 1 has discrete sound inlet openings 2, which are spaced along the shell of the tube and provided with a covering 3 of felt or woven fabric.
  • the sound inlet openings 2 are connected by passages 4 to the interior of the directional tube.
  • the column of air in the passages 2 constitutes an acoustic inductance, which acts on an air volume having a certain compliance (acoustic capacitance) so that an oscillatable system (springmass plug) is provided.
  • the oscillations of that system are damped by the friction of the air column at the passage surfaces and by the covering 3 of woven fabric or felt.
  • the directional tube is connected at 5 to a microphone capsule, which is not shown.
  • a chamber which precedes the diaphragm communicates directly with the interior of the directional tube.
  • the microphone capsule may be disposed directly in the directional tube.
  • the natural frequencies of the several spring-mass plug systems are selected to decrease as the distance from the microphone capsule increases. For this reason, the spring-mass plug systems shown in the right-hand part of the illustration must have a relatively large length.
  • each air inlet passage 4 is angled to form a non-straight acoustic line.
  • the frequency response of such spring mass plug system has two resonance frequencies, one of which is determined by the natural frequency of the air column which oscillates in the air passage whereas the second resonance frequency is determined by the air column in the air inlet passage (mass) and the air column between the inlet passage and the microphone diaphragm (spring).
  • the microphone according to the invention comprises three functionally significant sections.
  • the effective acoustic length of the tube is divided into two sections, which have approximately the same length and impart phase displacements of about 1r/2 and 1r/2 respectively, to the sound (see FIG. A relatively narrow section in which no phase displacement is effected and which has an increased sensitivity is disposed between said two sections (see FIG. 4).
  • the intermediate section is effective because the sound energies entering through the two other sections substantially cancel each other to 0 by interference.
  • the phase displacement of the sound energies entering through said two outer sections is further increased as a result of the transit time of the sound between the corresponding sound inlet openings and the canceling action is increased correspondingly.
  • the resulting directional patterns may be defined by the function L sin H l-c (1 cos a) and the mass plugs maintain the ratio L/A virtually constant.
  • each directional tube system has discrete sound inlet passages, which act as spring-mass plug systems. These systems should be tuned to provide the sensitivity distribution which is indicated in FIG. 6 whereas the phase-displacing action need not be utilized.
  • the pressures stated are in accordance with the binomial coefficient this results in a directional characteristic defined by k n (l cos a)" so that the directivity may be increased as desired by a decrease of n.
  • the spacing of the inlet openings is desirably increased in proportion with the wavelength. This may be accomplished with the aid of the impedance elements.
  • the increase in the directivity of that microphone is limited by the rapid decrease in sensitivity.
  • FIG. 7 is a diagrammaticperspective view showing another tubular directional pressure gradient microphone of this type.
  • the two directional tubes are composed each of three plates 7, 8, 9.
  • Each of the two outer ones of these plates (7 and 8) has a longitudinal passage 10, which communicates through openings 11, 12 with the chamber 14, which contains the microphone capsule 13.
  • the plates 7 are provided with air inlet passages 15.
  • the plate 9 closes the passage 10 and the air inlet passages except for a small inlet opening.
  • the openings of the air inlet passages are covered by a strip 16 of felt or woven fabric, which is inserted between the two plates 7 and 8 and ensures a damping action of the springmass plug systems.
  • a tubular directional microphone selective to a limited range of operating frequencies comprising an acoustic transducer capsule,
  • At least one tube having directional sound characteristics and selective to said range, said tube being coupled to said capsule,
  • each of said sound coupling means distributed along said tube and imparting the sensitivities to said portions of said tube, each of said sound coupling means extending between the inside and outside of said tube and having effective lengths, to sounds travelling through said sound coupling means, which lengths progressively change along the length of the tube, and
  • acoustic impedance elements in respective sound coupling means having respective cut-off frequencies which increase in one direction along the tube and respective natural response frequencies which decrease with increasing distance from the capsule, in which microphone the spacing of the second coupling means, their effective lengths and their acoustic impedance elements are so selected that sounds of the same frequency entering opposite end-portions of the tube via said means and emanating from a wave-front travelling parallel to the tube axis have a phase shift in the region of introduced between them so that such sounds have a selfcancelling effect on one another inside the tube.
  • said tubes are identical and extend side-by-side in the same direction with said sound coupling means extending along opposite sides of the tube combination, and
  • said capsule has a diaphragm on opposite sides of which sounds from the two tubes are respectively incident.
  • a tubular directional microphone as set forth in claim along 581d tube increases wlth distance from said p 13, in which the spacing of said acoustic impedance elements 5

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  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Details Of Audible-Bandwidth Transducers (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
US15082A 1969-03-04 1970-02-27 Tubular directional microphone Expired - Lifetime US3657490A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AT211569A AT284927B (de) 1969-03-04 1969-03-04 Rohrrichtmikrophon

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US3657490A true US3657490A (en) 1972-04-18

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AT (1) AT284927B (de)
DE (1) DE2008914A1 (de)
NL (1) NL7002947A (de)

Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4862507A (en) * 1987-01-16 1989-08-29 Shure Brothers, Inc. Microphone acoustical polar pattern converter
US5007091A (en) * 1987-04-23 1991-04-09 Utk Uuden Teknologian Keskus Oy Procedure and device for facilitating audiovisual observation of a distant object
WO1998026405A2 (en) * 1996-11-26 1998-06-18 American Technology Corporation Directed acoustic stick radiator
US20030008676A1 (en) * 2001-07-03 2003-01-09 Baumhauer John Charles Communication device having a microphone system with optimal acoustic transmission line design for improved frequency and directional response
US20090274329A1 (en) * 2008-05-02 2009-11-05 Ickler Christopher B Passive Directional Acoustical Radiating
US8553894B2 (en) 2010-08-12 2013-10-08 Bose Corporation Active and passive directional acoustic radiating
US8615097B2 (en) 2008-02-21 2013-12-24 Bose Corportion Waveguide electroacoustical transducing
US9451355B1 (en) 2015-03-31 2016-09-20 Bose Corporation Directional acoustic device
US20170230748A1 (en) * 2015-04-30 2017-08-10 Shure Acquisition Holdings, Inc. Offset cartridge microphones
US20170374443A1 (en) * 2016-06-22 2017-12-28 Bose Corporation Directional microphone integrated into device case
US10057701B2 (en) 2015-03-31 2018-08-21 Bose Corporation Method of manufacturing a loudspeaker
US10456556B2 (en) * 2018-02-19 2019-10-29 Bendit Technologies Ltd. Steering tool with enhanced flexibility and trackability
US11297423B2 (en) 2018-06-15 2022-04-05 Shure Acquisition Holdings, Inc. Endfire linear array microphone
US11297426B2 (en) 2019-08-23 2022-04-05 Shure Acquisition Holdings, Inc. One-dimensional array microphone with improved directivity
US11302347B2 (en) 2019-05-31 2022-04-12 Shure Acquisition Holdings, Inc. Low latency automixer integrated with voice and noise activity detection
US11303981B2 (en) 2019-03-21 2022-04-12 Shure Acquisition Holdings, Inc. Housings and associated design features for ceiling array microphones
US11310596B2 (en) 2018-09-20 2022-04-19 Shure Acquisition Holdings, Inc. Adjustable lobe shape for array microphones
US11310592B2 (en) 2015-04-30 2022-04-19 Shure Acquisition Holdings, Inc. Array microphone system and method of assembling the same
US11438691B2 (en) 2019-03-21 2022-09-06 Shure Acquisition Holdings, Inc. Auto focus, auto focus within regions, and auto placement of beamformed microphone lobes with inhibition functionality
US11445294B2 (en) 2019-05-23 2022-09-13 Shure Acquisition Holdings, Inc. Steerable speaker array, system, and method for the same
US11477327B2 (en) 2017-01-13 2022-10-18 Shure Acquisition Holdings, Inc. Post-mixing acoustic echo cancellation systems and methods
US11523212B2 (en) 2018-06-01 2022-12-06 Shure Acquisition Holdings, Inc. Pattern-forming microphone array
US11552611B2 (en) 2020-02-07 2023-01-10 Shure Acquisition Holdings, Inc. System and method for automatic adjustment of reference gain
US11558693B2 (en) 2019-03-21 2023-01-17 Shure Acquisition Holdings, Inc. Auto focus, auto focus within regions, and auto placement of beamformed microphone lobes with inhibition and voice activity detection functionality
US11706562B2 (en) 2020-05-29 2023-07-18 Shure Acquisition Holdings, Inc. Transducer steering and configuration systems and methods using a local positioning system
US11785380B2 (en) 2021-01-28 2023-10-10 Shure Acquisition Holdings, Inc. Hybrid audio beamforming system

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4421957A (en) * 1981-06-15 1983-12-20 Bell Telephone Laboratories, Incorporated End-fire microphone and loudspeaker structures

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2463762A (en) * 1941-11-14 1949-03-08 Automatic Elect Lab Electroacoustical transducer
US2856022A (en) * 1954-08-06 1958-10-14 Electro Sonic Lab Inc Directional acoustic signal transducer
DE1094803B (de) * 1959-01-16 1960-12-15 Sennheiser Electronic Rohrfoermiges Richtelement

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2463762A (en) * 1941-11-14 1949-03-08 Automatic Elect Lab Electroacoustical transducer
US2856022A (en) * 1954-08-06 1958-10-14 Electro Sonic Lab Inc Directional acoustic signal transducer
DE1094803B (de) * 1959-01-16 1960-12-15 Sennheiser Electronic Rohrfoermiges Richtelement

Cited By (44)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4862507A (en) * 1987-01-16 1989-08-29 Shure Brothers, Inc. Microphone acoustical polar pattern converter
US5007091A (en) * 1987-04-23 1991-04-09 Utk Uuden Teknologian Keskus Oy Procedure and device for facilitating audiovisual observation of a distant object
WO1998026405A2 (en) * 1996-11-26 1998-06-18 American Technology Corporation Directed acoustic stick radiator
WO1998026405A3 (en) * 1996-11-26 1999-02-18 American Tech Corp Directed acoustic stick radiator
US5940347A (en) * 1996-11-26 1999-08-17 Raida; Hans-Joachim Directed stick radiator
US20030008676A1 (en) * 2001-07-03 2003-01-09 Baumhauer John Charles Communication device having a microphone system with optimal acoustic transmission line design for improved frequency and directional response
US8615097B2 (en) 2008-02-21 2013-12-24 Bose Corportion Waveguide electroacoustical transducing
USRE48233E1 (en) 2008-05-02 2020-09-29 Bose Corporation Passive directional acoustic radiating
USRE46811E1 (en) 2008-05-02 2018-04-24 Bose Corporation Passive directional acoustic radiating
US8447055B2 (en) 2008-05-02 2013-05-21 Bose Corporation Passive directional acoustic radiating
US20110026744A1 (en) * 2008-05-02 2011-02-03 Joseph Jankovsky Passive Directional Acoustic Radiating
US8351630B2 (en) * 2008-05-02 2013-01-08 Bose Corporation Passive directional acoustical radiating
US20090274329A1 (en) * 2008-05-02 2009-11-05 Ickler Christopher B Passive Directional Acoustical Radiating
US8553894B2 (en) 2010-08-12 2013-10-08 Bose Corporation Active and passive directional acoustic radiating
US9451355B1 (en) 2015-03-31 2016-09-20 Bose Corporation Directional acoustic device
US10057701B2 (en) 2015-03-31 2018-08-21 Bose Corporation Method of manufacturing a loudspeaker
US20170230748A1 (en) * 2015-04-30 2017-08-10 Shure Acquisition Holdings, Inc. Offset cartridge microphones
US10009684B2 (en) * 2015-04-30 2018-06-26 Shure Acquisition Holdings, Inc. Offset cartridge microphones
US10547935B2 (en) 2015-04-30 2020-01-28 Shure Acquisition Holdings, Inc. Offset cartridge microphones
US11832053B2 (en) 2015-04-30 2023-11-28 Shure Acquisition Holdings, Inc. Array microphone system and method of assembling the same
US11678109B2 (en) 2015-04-30 2023-06-13 Shure Acquisition Holdings, Inc. Offset cartridge microphones
US11310592B2 (en) 2015-04-30 2022-04-19 Shure Acquisition Holdings, Inc. Array microphone system and method of assembling the same
US9888308B2 (en) * 2016-06-22 2018-02-06 Bose Corporation Directional microphone integrated into device case
US20170374443A1 (en) * 2016-06-22 2017-12-28 Bose Corporation Directional microphone integrated into device case
US11477327B2 (en) 2017-01-13 2022-10-18 Shure Acquisition Holdings, Inc. Post-mixing acoustic echo cancellation systems and methods
US10456556B2 (en) * 2018-02-19 2019-10-29 Bendit Technologies Ltd. Steering tool with enhanced flexibility and trackability
US11800281B2 (en) 2018-06-01 2023-10-24 Shure Acquisition Holdings, Inc. Pattern-forming microphone array
US11523212B2 (en) 2018-06-01 2022-12-06 Shure Acquisition Holdings, Inc. Pattern-forming microphone array
US11297423B2 (en) 2018-06-15 2022-04-05 Shure Acquisition Holdings, Inc. Endfire linear array microphone
US11770650B2 (en) 2018-06-15 2023-09-26 Shure Acquisition Holdings, Inc. Endfire linear array microphone
US11310596B2 (en) 2018-09-20 2022-04-19 Shure Acquisition Holdings, Inc. Adjustable lobe shape for array microphones
US11438691B2 (en) 2019-03-21 2022-09-06 Shure Acquisition Holdings, Inc. Auto focus, auto focus within regions, and auto placement of beamformed microphone lobes with inhibition functionality
US11558693B2 (en) 2019-03-21 2023-01-17 Shure Acquisition Holdings, Inc. Auto focus, auto focus within regions, and auto placement of beamformed microphone lobes with inhibition and voice activity detection functionality
US11303981B2 (en) 2019-03-21 2022-04-12 Shure Acquisition Holdings, Inc. Housings and associated design features for ceiling array microphones
US11778368B2 (en) 2019-03-21 2023-10-03 Shure Acquisition Holdings, Inc. Auto focus, auto focus within regions, and auto placement of beamformed microphone lobes with inhibition functionality
US11800280B2 (en) 2019-05-23 2023-10-24 Shure Acquisition Holdings, Inc. Steerable speaker array, system and method for the same
US11445294B2 (en) 2019-05-23 2022-09-13 Shure Acquisition Holdings, Inc. Steerable speaker array, system, and method for the same
US11688418B2 (en) 2019-05-31 2023-06-27 Shure Acquisition Holdings, Inc. Low latency automixer integrated with voice and noise activity detection
US11302347B2 (en) 2019-05-31 2022-04-12 Shure Acquisition Holdings, Inc. Low latency automixer integrated with voice and noise activity detection
US11750972B2 (en) 2019-08-23 2023-09-05 Shure Acquisition Holdings, Inc. One-dimensional array microphone with improved directivity
US11297426B2 (en) 2019-08-23 2022-04-05 Shure Acquisition Holdings, Inc. One-dimensional array microphone with improved directivity
US11552611B2 (en) 2020-02-07 2023-01-10 Shure Acquisition Holdings, Inc. System and method for automatic adjustment of reference gain
US11706562B2 (en) 2020-05-29 2023-07-18 Shure Acquisition Holdings, Inc. Transducer steering and configuration systems and methods using a local positioning system
US11785380B2 (en) 2021-01-28 2023-10-10 Shure Acquisition Holdings, Inc. Hybrid audio beamforming system

Also Published As

Publication number Publication date
AT284927B (de) 1970-10-12
NL7002947A (de) 1970-09-08
DE2008914A1 (de) 1970-09-10

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