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EP0077615B1 - Ecran pour microphone à électrète - Google Patents

Ecran pour microphone à électrète Download PDF

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Publication number
EP0077615B1
EP0077615B1 EP82305196A EP82305196A EP0077615B1 EP 0077615 B1 EP0077615 B1 EP 0077615B1 EP 82305196 A EP82305196 A EP 82305196A EP 82305196 A EP82305196 A EP 82305196A EP 0077615 B1 EP0077615 B1 EP 0077615B1
Authority
EP
European Patent Office
Prior art keywords
casing
electret microphone
electret
further characterised
film
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
Application number
EP82305196A
Other languages
German (de)
English (en)
Other versions
EP0077615A1 (fr
Inventor
Guy John Chaput
Edward Matthew Sich
Beverley William Thomas Gumb
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.)
Nortel Networks Ltd
Original Assignee
Northern Telecom Ltd
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 Northern Telecom Ltd filed Critical Northern Telecom Ltd
Publication of EP0077615A1 publication Critical patent/EP0077615A1/fr
Application granted granted Critical
Publication of EP0077615B1 publication Critical patent/EP0077615B1/fr
Expired legal-status Critical Current

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Classifications

    • 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
    • H04R1/08—Mouthpieces; Microphones; Attachments therefor
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/01—Electrostatic transducers characterised by the use of electrets
    • H04R19/016—Electrostatic transducers characterised by the use of electrets for microphones

Definitions

  • This invention relates to electret microphones particularly for use in telephones.
  • Telephone electret microphones need to be shielded from electromagnetic interference to which the microphone is subjected in normal use. Such fields existing in the home, for example, are radiated from nearby television and radio transmitters and from electric motors.
  • the microphone components are surrounded by, and the electret element shielded by, an aluminium casing.
  • One or more circular holes in the surface of the casing allows transmission of acoustic waves to the electret elements.
  • the electret element is subjected to a distorted electric field due to body capacitance.
  • the output from the electret element is taken to an amplifier and then to a balanced line, balanced line transmission being used to compensate for interference occurring in the transmission path.
  • unbalance produced by a distorted field at the electret element will not be compensated and is seen as a component of the acoustic signal. Consequently, shielding of all interference at the microphone, including that produced by body capacitance, is necessary.
  • a known electret microphone used in a telephone consists of the following components.
  • the top component which, in use, is located nearest the speaker's mouth, is one part of a two-part aluminium casing.
  • the casing has a hole through its center to allow passage of acoustic waves.
  • Beneath this casing part is a moisture barrier which is normally a thin film of plastic material such as Mylar (registered Trade Mark) which is pressed into sealing engagement with the top part of the casing.
  • Mylar registered Trade Mark
  • Below the moisture barrier and a compressible mounting ring for the moisture barrier lies the electret element which, together with associated electrical components, seats within a second part of the aluminium casing.
  • an electret microphone comprising a casing, electret element within the casing for producing an electrical signal corresponding to acoustic vibration passing into the casing through a passage therein and a film blocking the passage, characterised in that the film which blocks the passage is at least partially formed from a conducting film which is transparent to said acoustic vibration and electrically contacts a fixed potential body whereby to fix the potential of the conducting film.
  • the component comprises a substrate plastic film, the film having a conductive coating deposited thereon.
  • the microphone illustrated has a top ferrule or casing part 10 having a passage 11.
  • the ferrule is made of aluminium. It has an upper ridge 12 which can engage an internal threaded part of a telephone handset housing (not shown).
  • An upwardly pressed annular portion 14 accommodates and centers a sealing washer 16.
  • the sealing washer 16 presses a combined moisture barrier and shield element 18 into the recessed portion 14.
  • the element 18 has an upper conductive surface 20.
  • the element is manufactured by vacuum-depositing a thin layer of aluminium onto a plastic film 21, such as Mylar of a thickness of 10 um. The thickness and flexibility of the element 18 is such that it is rendered transparent to acoustic vibrations of between 10 Hz and 4 KHz.
  • the sealing washer 16 acts to tension the element 18. If the element is improperly mounted, then there is a risk of its affecting the voice frequency vibration transmitted by it.
  • the transducer element 22 comprises a top frame 24 which clamps a piece of electret foil 26 against a bottom plate 28 by means of clips 29.
  • the foil has a metallic top surface and a bottom layer which has the property of being able to store a charge for extended periods.
  • the structure of the electret is well-known.
  • the charge storage face is separated from a conducting layer 30 on the back plate 28 by 50 microns thick strips of dielectric film 32.
  • the plate 28 in the region of the conducting layer is formed with holes 34 to permit the electret to vibrate in response to acoustic waves passing into the microphone.
  • the potential difference between the conducting layer 30 and the conducting surface of the electret varies to give an electric analog of the voice frequency vibration.
  • a printed conductor on board 36 which has wire leads 37 bonded to the electrical surfaces of the electret element 22, the varying electret voltage is taken to a field effect transistor (not shown) mounted on the reverse surface of the bord.
  • the field effect transistor projects into a chamber 40 which is formed in a bottom part 42 of the aluminum casing.
  • the chamber size is chosen to optimize vibration of the electret foil 26.
  • Contacts (not shown) are also formed on the reverse surface of the board 36 and communicate electrically with the circuit formed on the board upper face. The contacts project through a passage 46 in the casing part 42.
  • a second seal 48 which surrounds the contacts protects the inside of the microphone from adverse environmental conditions.
  • the casing comprising ferrule 10 and bottom part 42 is grounded via one of the conductors on board 36, and so, consequently, is the top surface of the element 18.
  • the element 18 thus functions to seal the microphone from moisture and gaseous contaminants and acts also to make the electromagnetic shield around the electret element complete.
  • the primary affect of this additional shielding part is in reducing the interference of that electric field produced by body capacitance which would otherwise affect the electret microphone output transmitted to a balanced line.
  • the element 18 could, instead, be a single layer of conducting foil.
  • Aluminum is particularly preferred as a conducting coating for the element 18 firstly, since it is easily vacuum-deposited on a plastic substrate, secondly, since the ferrule is also made of aluminum and therefor would not form an electric cell with the coating when damp, and lastly, since aluminum is a good conductor.
  • other conductors such as copper or zinc may be preferred, or the element may alternatively be composed of a carbon loaded plastic.
  • the top surface of the element 18 is made conducting and that surface contacts the grounded ferrule 10. In other arrangements it may be preferred not to ground the casing around the electret in which case the conductive coating on the element 18 is made to contact a grounded or other fixed potential body.
  • the conductive coating extends over the full surface area of the element 18 so as to completely surround the transducer element 22 with an electromagnetic shield.
  • a conductive coating can be deposited on both sides of the element 18 in order to facilitate assembly.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
  • Telephone Set Structure (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)

Claims (10)

1. Microphone à électret comprenant un boîtier, un élément d'électret (11) à l'intérieur du boîtier pour produire un signal électrique correspondant aux vibrations acoustiques entrant dans le boîtier par l'intermédiaire d'un canal (11) ménagé dans ce boîtier, et une pellicule (18) bloquant le canal (11), caractérisé en ce que la pellicule (18) bloquant le canal (11) est constitué au moins partiellement d'une pellicule conductrice (18) qui est transparente vis-à-vis des vibrations acoustiques et est en contact électrique avec un corps (10) de potentiel fixe, d'où il résulte la fixation du potentiel de la pellicule conductrice (18).
2. Microphone à électret selon la revendication 1, caractérisé en outre en ce que la pellicule conductrice comporte une couche conductrice (20) déposée sur un substrat (21).
3. Microphone à électret selon la revendication 2, caractérisé en outre en ce que la couche conductrice (20) est déposée sur les côtés opposés d'un substrat (21) en lamelles.
4. Microphone à électret selon la revendication 2, caractérisé en outre en ce que le substrat (21) est une pellicule de materiau plastique flexible.
5. Microphone à électret selon la revendication 4, caractérisé en outre en ce que la pellicule (18) comprenant le substrat en matériau plastique supportant la couche conductrice déposée (20) est imperméable à l'humidité.
6. Microphone à électret selon la revendication 5, caractérisé en outre en ce qu'un élément d'étanchéité (16) comprime la combinaison du substrat (21) et de la couche conductrice (20) pour la mettre en contact avec une surface intérieure du boîtier (10).
7. Microphone à électret selon la revendication 1, caractérisé en outre en ce que le boîtier (10) est conducteur et mis à la masse, et la pellicule conductrice (18) est en contact électrique avec une surface intérieure du boîtier (10).
8. Microphone à électret selon la revendication 7, caractérisé en outre en ce que tant la pellicule conductrice (18) que le boîtier (10) sont en aluminium.
9. Microphone à électret selon la revendication 1, caractérisé en outre en ce que la pellicule conductrice (18) est constituée d'un matériau plastique chargé d'un conducteur.
10. Microphone à électret selon la revendication 9, caractérisé en outre en ce que le conducteur est du carbone.
EP82305196A 1981-10-19 1982-09-30 Ecran pour microphone à électrète Expired EP0077615B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA388183 1981-10-19
CA000388183A CA1165859A (fr) 1981-10-19 1981-10-19 Blindage pour microphone a electret

Publications (2)

Publication Number Publication Date
EP0077615A1 EP0077615A1 (fr) 1983-04-27
EP0077615B1 true EP0077615B1 (fr) 1986-04-30

Family

ID=4121192

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82305196A Expired EP0077615B1 (fr) 1981-10-19 1982-09-30 Ecran pour microphone à électrète

Country Status (7)

Country Link
EP (1) EP0077615B1 (fr)
JP (1) JPS5881000A (fr)
KR (1) KR880000963B1 (fr)
CA (1) CA1165859A (fr)
DE (1) DE3270879D1 (fr)
DK (1) DK153619C (fr)
IE (1) IE53590B1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8169041B2 (en) 2005-11-10 2012-05-01 Epcos Ag MEMS package and method for the production thereof
US8184845B2 (en) 2005-02-24 2012-05-22 Epcos Ag Electrical module comprising a MEMS microphone
US8229139B2 (en) 2005-11-10 2012-07-24 Epcos Ag MEMS microphone, production method and method for installing
US8582788B2 (en) 2005-02-24 2013-11-12 Epcos Ag MEMS microphone

Families Citing this family (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2218298A (en) * 1987-11-28 1989-11-08 Anthony David Heyes An ultra-sonic pulse-echo ranging device
DE19715365C2 (de) * 1997-04-11 1999-03-25 Sennheiser Electronic Kondensatormikrofon
US7434305B2 (en) 2000-11-28 2008-10-14 Knowles Electronics, Llc. Method of manufacturing a microphone
US7166910B2 (en) * 2000-11-28 2007-01-23 Knowles Electronics Llc Miniature silicon condenser microphone
US7439616B2 (en) 2000-11-28 2008-10-21 Knowles Electronics, Llc Miniature silicon condenser microphone
US8629005B1 (en) 2000-11-28 2014-01-14 Knowles Electronics, Llc Methods of manufacture of bottom port surface mount silicon condenser microphone packages
US6781231B2 (en) 2002-09-10 2004-08-24 Knowles Electronics Llc Microelectromechanical system package with environmental and interference shield
JP4452584B2 (ja) * 2004-08-31 2010-04-21 株式会社オーディオテクニカ コンデンサマイクロホン
KR20080011066A (ko) * 2006-07-27 2008-01-31 스타 마이크로닉스 컴퍼니 리미티드 마이크로폰의 케이싱 및 콘덴서 마이크로폰
US7894622B2 (en) 2006-10-13 2011-02-22 Merry Electronics Co., Ltd. Microphone
PH12014500968A1 (en) 2011-11-04 2014-06-09 Knowles Electronics Llc Embedded dielectric as a barrier in an acoustic device and method of manufacture
US9078063B2 (en) 2012-08-10 2015-07-07 Knowles Electronics, Llc Microphone assembly with barrier to prevent contaminant infiltration
US9794661B2 (en) 2015-08-07 2017-10-17 Knowles Electronics, Llc Ingress protection for reducing particle infiltration into acoustic chamber of a MEMS microphone package

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3787642A (en) * 1971-09-27 1974-01-22 Gte Automatic Electric Lab Inc Electrostatic transducer having resilient electrode
US3778561A (en) * 1972-06-21 1973-12-11 Bell Canada Northern Electric Electret microphone
JPS5419172B2 (fr) * 1973-07-23 1979-07-13
JPS5717013Y2 (fr) * 1977-07-11 1982-04-09
US4188513A (en) * 1978-11-03 1980-02-12 Northern Telecom Limited Electret microphone with simplified electrical connections by printed circuit board mounting

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
THE BELL SYSTEM JOURNAL, vol. 58, no. 7, September 1979, pages 1557-1577, New York (USA); J.C. BAUMHAUER Jr. et al.: "The EL2 electret transmitter: analytical modeling, optimization and design". *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8184845B2 (en) 2005-02-24 2012-05-22 Epcos Ag Electrical module comprising a MEMS microphone
US8582788B2 (en) 2005-02-24 2013-11-12 Epcos Ag MEMS microphone
US8169041B2 (en) 2005-11-10 2012-05-01 Epcos Ag MEMS package and method for the production thereof
US8229139B2 (en) 2005-11-10 2012-07-24 Epcos Ag MEMS microphone, production method and method for installing
US8432007B2 (en) 2005-11-10 2013-04-30 Epcos Ag MEMS package and method for the production thereof

Also Published As

Publication number Publication date
DK450682A (da) 1983-04-20
DE3270879D1 (en) 1986-06-05
KR840002387A (ko) 1984-06-25
IE53590B1 (en) 1988-12-21
CA1165859A (fr) 1984-04-17
KR880000963B1 (ko) 1988-06-04
IE822516L (en) 1983-04-19
DK153619C (da) 1988-12-19
EP0077615A1 (fr) 1983-04-27
JPS5881000A (ja) 1983-05-16
DK153619B (da) 1988-08-01

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