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EP 0 222 813 B1 |
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EUROPEAN PATENT SPECIFICATION |
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Mention of the grant of the patent: |
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28.02.1990 Bulletin 1990/09 |
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Date of filing: 09.05.1986 |
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International application number: |
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PCT/GB8600/257 |
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International publication number: |
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WO 8606/918 (20.11.1986 Gazette 1986/25) |
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(54) |
IMPROVEMENTS IN OR RELATING TO MICROPHONES
VERBESSERUNGEN AN ODER BETREFFEND MIKROPHONE
AMELIORATION APPORTEE A DES MICROPHONES
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Designated Contracting States: |
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AT BE CH DE FR GB IT LI LU NL SE |
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Priority: |
09.05.1985 GB 8511767
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Date of publication of application: |
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27.05.1987 Bulletin 1987/22 |
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Proprietor: AB Electronic Components Limited |
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Mountain Ash
Mid-Glamorgan CF45 4SF
Wales (GB) |
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Inventor: |
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- ADAMS, Kevin, Michael, McKeown
Wakefield
West Yorkshire (GB)
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(74) |
Representative: Holliday, Frank |
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MARKS & CLERK,
57-60 Lincoln's Inn Field London WC2A 3LS London WC2A 3LS (GB) |
(56) |
References cited: :
DE-A- 2 261 600 GB-A- 2 016 861
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GB-A- 1 515 287
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Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
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Background of the Invention
[0001] The present invention relates to microphones and more particularly to a noise cancelling
microphone.
[0002] Noise cancelling microphones are in the main required for communications use in environments
where there is a high ambient noise level. Such microphones are designed to discriminate
against interference in the form of distant noise sources and to discriminate in favour
of close speech sounds. They are constructed so as to be sensitive to the pressure
gradient of the sound field in their vicinity, thereby discriminating between close
sources which produce a large pressure gradient and distant sources which produce
a small pressure gradient. In addition, the microphones are normally mounted on a
headset boom so as to allow close positioning to the user's mouth and hence maximise
the speech sound signal level available.
[0003] One known form of noise cancelling microphone employs a piezoelectric transducer
in which an electrical output is obtained using acoustic pressure to mechanically
deform a diaphragm made from a piezoelectric material. Such microphones are disclosed
in our UK Patent Specification No. 1 515 287 which describes both first order pressure
gradient and second order pressure gradient noise cancelling microphones employing
piezoelectric transducers. The noise cancelling function requires that the construction
of the inside of the microphones and the location of their diaphragms be highly symmetric
so that cancellation of equal opposite sound pressure due to distant interference
sources can occur.
Summary of the Invention
[0004] An objective of the present invention is to provide a noise cancelling device in
the form of a pressure gradient microphone employing a piezoelectric material as a
transducer, the microphone providing noise cancelling performances superior to that
of currently available microphones.
[0005] According to the present invention there is provided a microphone having a piezoelectric
transducer element contained within a housing, the transducer element being in the
form of a diaphragm of piezoelectric material having at least two arms extending therefrom,
each arm providing a respective electrically conductive path to a respective part
of the diaphragm, the housing comprising two mutually engageable housing parts between
which the diaphragm is sandwiched during assembly to divide the housing into two separate
chambers, each housing part having one or more sound vents for admitting sound to
a respective one of the chambers, the housing parts being designed so that when they
are assembled together the resulting housing defines within its structure at least
two guide channels each of which is provided for receiving a respective one of the
arms extending from the diaphragm.
[0006] In one embodiment two sound vents are provided in each housing part, the two sound
vents being disposed opposite to one another such that the complete housing when assembled
may provide part of a second order pressure gradient microphone.
[0007] In a preferred embodiment of the present invention each of the mutually engageable
housing parts have identical features. Conveniently each housing part is manufactured
from a plastics material using an injection moulding process.
[0008] In a specific embodiment of the present invention each housing part has an aperture,
preferably cylindrical in shape, extending through its centre, each of two longitudinal
side walls of the housing part being formed with a respective elongate groove portion,
two other longitudinal side walls of the housing part each carrying a respective arm
complementary with the groove portions thereby enabling two housing parts to be assembled
together by sliding the arms of one housing part into the groove portions of the other
housing part.
[0009] In a preferred embodiment of the present invention each arm of at least one of the
housing parts has a respective channel formed on its inside facing surface whereby,
after assembly of the two housing parts into the assembled housing, the assembled
housing defines within two side walls the two guide channels for receiving the arms
of the diaphragm. Two electrical contacts may also be provided, each contact having
a portion adapted to be received in the guide channel and having a curved end portion
for abutting against, within the guide channel, an electrically conductive surface
of one of the arms extending from the diaphragm, the electrically conductive surface
forming an electrical path to a metallised electrode on a surface of the diaphragm.
Each electrical contact also has a terminal end adapted for extending out of the guide
channel for connection into a socket associated with a pre-amplifier circuit.
[0010] In a referred embodiment at least two membranes are provided for each sound vent,
one of the membranes serving to protect the sound vent from the environment and the
other membrane serving to damp the sound before entering the sound vent.
Brief Description of the Drawings
[0011] The present invention will be described further, by way of example, with refernce
to the accompanying drawings in which:
Figure 1 illustrates diagrammatically a noise-cancelling microphone not in accordance
with the present invention,
Figure 2 is a perspective view of a complete noise-cancelling microphone in accordance
with one embodiment of the present invention,
Figure 3 is an exploded view of the microphone of Figure 2,
Figure 4 is an exploded view of the microphone capsule in Figure 3, and
Figure 5 is a representation of an electrical contact which can be used in place of
the contact shown in Figure 4.
[0012] Referring to Figure 1 of the drawings the microphone comprises a cylindrical housing
1 in which is contained a piezoelectric transducer. The piezoelectric transducer comprises
a diaphragm 10 of piezoelectric material extending across the interior of the housing
1 to define therein two chambers 3 and 5, the diaphragm 10 being provided with metal
electrodes (not shown) on each of its major surfaces across which an electrical output
is developed when the diaphragm 10 is mechanically deformed.
[0013] Four sound vents 2, 4, 6 and 8 are provided through the cylindrical wall of the housing
1 to allow sound pressure to act on the major surfaces of the diaphragm 10. The sound
vents 2 and 8 together with the diaphragm 10 form one first order pressure gradient
unit and the sound vents 4 and 6 together with the diaphragm 10 form a second first
order pressure gradient unit. By having the sound vents which are opposite to each
other admitting pressures to the same surface of the diaphragm 10, the resultant force
acting on the diaphragm 10 is the difference of the forces obtained from the two first
order pressure gradient combinations; the effective force on the diaphragm 10 is then
proportional to the second order of the pressure gradient which is the characteristic
of a second order pressure gradient microphone.
[0014] In order to provide a microphone having a noise cancelling performance of high quality
the necessary requirements are to arrange for each chamber to be as near identical
as possible in its shape and volume, for the diaphragm to be accurately mounted within
the housing and for good electrical connection to be maintained between the metal
electrodes on the major surfaces of the diaphragm and external pre-amplifier circuitry.
The need for these requirements has given rise to embodiments of the present invention
which are described below.
Description of a Preferred Embodiment
[0015] Referring to Figures 2 and 3 of the drawings a complete microphone according to one
embodiment of the present invention comprises a microphone capsule 12 in which is
housed a piezoelectric transducer, a protective stainless steel mesh 14 which also
serves to shield the transducer from outside electrical noise and a protective capsule
cover 16. The piezoelectric transducer is in the form of a diaphragm of polyvinylidene
fluoride (PVdF) having surfaces coated in gold or aluminium to define metallised surfaces.
The material used for the microphone capsule 12 is advantageously CYCOLAC LA (Trade
mark of Borg-War- ner Corporation) which is a low temperature impact resistant material
designed for injection moulding and having a desirable coefficient of linear expansion
within the range 110 to 120 x 10'
6 K.
[0016] Terminal ends 21, 23 of electrical contacts project from a side plate 22 of the capsule
12 to define a plug assembly for engagement within a socket 24 of a pre-amplifier
26, circuit 26 being of known type.
[0017] Referring to Figure 4 of the drawings the microphone capsule comprises two identically
formed, mutually engageable plastic housing parts 30, 32. As each of the parts 30,
32 is identical their description hereinafter will be primarily with reference to
the part 30, occasional reference being made to features of the part 32 when necessary.
[0018] The part 30 has a generally oblong shaped body which is manufactured by an injection
moulding process, the internal and external dimensions of each part conforming to
fine tolerances. The part 30 has a cylindrically shaped aperture 34 extending through
its centre, the aperture 34 and the internal walls of the part 30 together defining,
after assembly of the capsule, a chamber on one side of the diaphragm of the piezoelectric
material. Each of two longitudinal external side walls of the part 30 are formed with
a respective elongate rectangular groove portion 36 38; the other two longitudinal
side walls 37, 39 each carrying a respective arm 40, 42. The arms 40, 42 each have
a respective channel formed on their inside facing surfaces, the channels being identical
to a pair of channels 44, 46 shown on the part 32. Each side wall 37, 39 is provided
with a respective sound vent, sound vent 48 being shown for side wall 37, extending
through the respective side wall to the central aperture 34 thereby forming a conduit
through which sound waves may be admitted to the central aperture 34.
[0019] Each of the arms 40, 42 on the part 30 is dimensioned be complementary with the rectangular
groove portions on the part 32 thereby enabling the parts 30, 32 to be snugly fitted
together by sliding the arms 40, 42 into the groove portions and to define within
the side walls of the complete capsule housing two guide channels.
[0020] The transducer element is formed from a piezoelectric plastics material such as polyvinylidene
fluoride (PVdF) and comprises two circular layers 52 and 54 of PVdF which together
form a laminate, each layer 52 and 54 having an integral arm 56 and 58 respectively
made also of PVdF. The laminate when sandwiched between the housing parts 30, 32 so
as to cover the aperture 34, serves as a diaphragm separating the two chambers defined
within the capsule housing. Each of the arms 56 and 58 is received in a respective
one of the guide channels defined in the side walls of the assembled capsule housing.
[0021] The diaphragm is provided with metallised electrodes on opposing sides and each arm
is also metallised to provide an electrically conductive path from each of the metallised
electrodes.
[0022] Two electrical contacts 60 are also provided for insertion along the respective guide
channels defined in the side walls of the capsule housing. The electrical contacts
60 are inserted into the ends of the guide channels remote from the diaphragm and
are provided with curved end portions for abutting against and for providing maximum
pressure engagement with the metallised surfaces of the arms 56 and 58. In this way
compensation is provided for any thermal mismatch between the different materials
of the arms 56, 58 and the contacts 60. Two types of contact 60 are illustrated in
Figures 4 and 5.
[0023] Referring to Figure 4 the contact 60 is formed as a single shaped metal part having
its terminal end 23 rolled into a pin contact. The pin contact is connected to an
oblong portion 27 the width of which conforms to the width of the groove portions
36, 38 in the housing part 30 and the other end of the contact 60 has its remote end
portion 25 curved in a direction away from the plane defined by the oblong portion
27.
[0024] Referring to Figure 5 the contact 60 is manufactured as a two part contact, one part
being the terminal end 23 which is in the form of a solid wire. The other part comprises
the oblong portion 27 having an abutment 29 and the curved portion 25. One end of
the solid wire is spot welded to the abutment 29 extending from the oblong portion
27.
[0025] The curved end portion 25 in Figure 5, is considerably longer to that of the curved
end portion of the contact shown in Figure 4, the longer curved end portion 25 being
found in practice to compensate better for any thermal mismatch that may arise.
[0026] The two housing parts 30, 32 are covered at their ends by side plates 22, 24, the
side plates 22, 24 and the housing parts 30, 32 being held together by four long pins
70. The pins 70 extend through holes 72 and 76 formed through the corner regions of
the side plates 22, 24 and through elongate holes 74, 75 formed through the corner
shoulders of the housing parts 30, 32. Additionally or alternatively the housing parts
30, 32 may be glued together. The terminal ends 23 of the electrical contacts 60 project
through holes 80 in the side plate 22 and through holes 82 formed in a silicon sealing
gasket 84. The gasket 84 mates with a plastic housing end 25 of the pre-amplifier
26 to prevent moisture reaching the terminal ends 21, 23.
[0027] Four small vents 90 are provided in the side plate 24 each of which is positioned
between adjacent pairs of the holes 76, and aligned with the guide channels in the
side walls of the capsule housing via respective vents 91 in the housing part 32.
The small vents 90 and 91 serve to equalise the ambient barometric pressure within
the two chambers defined within the capsule housing. A small resilient ring-shaped
grommet 92 is also provided for location between the side plate 24 and the back surface
of the capsule cover 16 to serve as a pressure pad for the housing parts 30,32.
[0028] Each of the sound vents is covered by a sound damping membrane 94 made from a polyester
cloth and each membrane 94 is covered by a further membrane 96 mounted in an oblong
frame.
[0029] The membranes 96 serve to protect the sound vents and the membranes 94 from the outside
environment but must also be sufficiently compliant to allow sound to be transmitted
into the sound vents. The membranes 96 may suitably be formed from a silicon web moulding.
The metal mesh 14 (see figure 3) serves to both shield the transducer from outside
electrical noise and to protect the membranes 94, 96 from dirt and thereby aids cleaning.
1. A microphone having a piezoelectric transducer element contained within a housing,
the transducer element being in the form of a diaphragm of piezoelectric material
characterised in that the diaphragm has at least two arms extending therefrom, each
arm (56, 58) providing a respective electrically conductive path to a respective part
of the diaphragm, the housing comprising two mutually engageable housing parts (30,
32) between which the diaphragm is sandwiched during assembly to divide the housing
into two separate chambers, each housing part (30, 32) having one or more sound vents
(48) for admitting sound to a respective one of the chambers, the housing parts (30,
32) being designed so that when they are assembled together the resulting housing
defines within its structure at least two guide channels each of which is provided
for receiving a respective one of the arms (56, 58) extending from the diaphragm.
2. A microphone as claimed in claim 1 characterised in that two sound vents (48) are
provided in each housing part, (30, 32) the two sound vents (48) being disposed opposite
to one another such that the complete housing when assembled may provide part of a
second order pressure gradient microphone.
3. A microphone as claimed in claim 1 or claim 2 characterised in that each of the
mutually engageable housing parts (30, 32) are formed with identical features.
4. A microphone as claimed in any one of claims 1 to 3 characterised in that each
part (30, 32) is manufactured from a plastics material using an injection moulding
process.
5. A microphone as claimed in claim 4 characterised in that the material has a coefficient
of linear expansion, substantially within the range 110 to 120 x 10 K.
6. A microphone as claimed in any one of claims 1 to 5 characterised in that each
housing part (30, 32) has an aperture (34) extending through its centre, each of two
longitudinal side walls of the housing part (30, 32) being formed with a respective
elongate groove portion, (36, 38) two other longitudinal side walls (37, 39) of the
housing part (30, 32) each carrying a respective arm (40, 42) complementary with the
groove portions (36, 38) thereby enabling two housing parts (30, 32) to be assembled
together by sliding the arms (40, 42) of one housing part (30, 32) into the complementary
groove portions (36, 38) of the other housing part (30, 32).
7. A microphone as claimed in claim 6 characterised in that the aperture extending
through the centre of the housing part (30, 32) is substantially cylindrical in shape.
8. A microphone as claimed in claim 6 or claim 7 characterised in that each arm (40,
42) of the housing part (30, 32) has a respective channel (44, 46) formed on its inside
facing surface whereby, after assembly of the two housing parts (30, 32) into the
assembled housing, the assembled housing defines within two side walls the two guide
channels for receiving the two arms (56, 58) extending from the diaphragm.
9. A microphone as claimed in claim 8 characterised in that two electrical contacts
(60) are provided, each contact (60) having a portion adapted to be received in the
guide channel and having a curved end portion (25) for abutting against, within the
guide channel, an electrically conductive surface of one of the arms (56, 58) extending
from the diaphragm, the electrically conductive surface forming an electrical path
to a metallised electrode on a surface of the diaphragm, each electrical contact also
having a terminal end (23) adapted for extending out of the guide channel for connection
into a socket associated with a pre-amplifier circuit (26).
10. A microphone as claimed in any one of claims 1 to 9 characterised in that at least
two membranes (94, 96) are provided for each sound vent, (48) one of the membranes
(96) serving to protect the sound vent from the environment and the other membrane
(94) serving to damp the sound before entering the sound vent (48).
1. Mikrofon mit einem innerhalb eines Gehäuses angeordneten piezoelektrischen Wandlerelement,
das als Membran aus einem piezoelektrischen Werkstoff ausgebildet ist, dadurch gekennzeichnet,
dass die Membran mindestens zwei sich von dieser weg erstreckende Arme hat, jeder
Arm (56, 58) jeweils eine elektrisch leitende Bahn zu einem zugeordneten Teil der
Membran bildet, das Gehäuse zwei miteinander in Eingriff bringbare Gehäuseteile (30,
32) umfasst, zwischen denen die Membran bei der Montage eingelegt wird, um das Gehäuse
in zwei getrennte Kammern zu unterteilen, jeder Gehäuseteil (30, 32) eine oder mehrere
Schallöffnungen (48) aufweist, um Schall in eine jeweilige Kammer einzulassen, und
die Gehäuseteile so ausgeführt sind, dass nach ihrem Zusammenbau das resultierende
Gehäuse innerhalb seines Aufbaus mindestens zwei Führungskanäle bildet, von denen
jeder vorgesehen ist, um einen jeweiligen der sich von der Membran weg erstreckenden
Arme (56, 58) aufzunehmen.
2. Mikrofon nach Anspruch 1, dadurch gekennzeichnet dass zwei Schallöffnungen (48)
in jedem Gehäuseteil (30, 32) vorgesehen sind, die derart einander gegenüberliegend
angebracht sind, dass das vollständige Gehäuse nach dem Zusammenbau Teil eines Mikrofons
für Schalldruck zweiter Ordnung bilden kann.
3. Mikrofon nach Anspruch 1 oder 2, dadurch gekennzeichnet dass jeder der gegenseitig
in Eingriff stehenden Gehäuseteile (30, 32) mit identischen Merkmalen ausgebildet
ist.
4. Mikrofon nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet dass jeder Teil
(30, 320) aus Kunststoff unter Verendung eines Spritzgussverfahrens hergestellt ist.
5. Mikrofon nach Anspruch 4, dadurch gekennzeichnet dass der Kunststoff einen linearen
Ausdehnungskoeffizienten im wesentlichen innerhalb eines Bereiches von 110 bis 120
x 107r' K7' hat.
6. Mikrofon nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet dass jeder Gehäuseteil
(30, 32) eine sich durch seinen Mittelpunkt erstreckende Öffnung (34) hat, dass jeder
der beiden Seitenlängswände des Gehäuseteils (30, 32) jeweils mit einem Längsnutabschnitt
(36, 38) ausgebildet ist, dass zwei weitere Längsseitenwände (37, 39) des Gehäuseteils
(30, 32) jeweils einen Arm (40, 42) aufweisen, der komplementär zu den Längsnutabschnitten
(36, 38) ist, um dadurch den Zusammenbau der beiden Gehäuseteile (30, 32) zu ermöglichen,
indem die Arme (40, 42) des einen Gehäuseteils (30, 32) in die komplementären Längsnutabschnitte
(36, 38) des anderen Gehäuseteils (30,32) eingeschoben werden.
7. Mikrofon nach Anspruch 6, dass die sich durch den Mittelpunkt des Gehäuseteils
(30, 32) erstreckende Öffnung eine im wesentlichen zylindrische Form hat.
8. Mikrofon nach Anspruch 6 oder 7, dadurch gekennzeichnet dass jeder Arm (40, 42)
des Gehäuseteils (30, 32) einen an seiner nach innen gerichteten Oberfläche jeweils
einen Kanal (44, 46) hat, so dass nach dem Zusammenbau der beiden Gehäuseteile (30,
32) in das montierte Gehäuse dieses innerhalb der beiden Seitenwände die beiden Führungskanäle
zur Aufnahme der beiden Arme (56, 58) bildet, die sich von der Membran weg erstrecken.
9. Mikrofon nach Anspruch 8, dadurch gekennzeichnet dass zwei elektrische Kontakte
(60) vorgesehen sind, wovon jeder einen Abschnitt aufweist, der im Führungskanal aufgenommen
werden kann und der einen gekrümmten Endabschnitt (25) hat, der sich innerhalb des
Führungskanals gegen eine elektrisch leitende Fläche eines der sich von der Membran
weg erstreckenden Arme (56, 58) legt, dass die elektrisch leitende Fläche eine elektrische
Bahn zu einer metallisierten Elektrode auf einer Oberfläche der Membran bildet, und
jeder elektrische Kontakt ferner ein Abschlussende (23) hat, das sich aus dem Führungskanal
erstreckt und mit einer Buchse verbindbar ist, die einer Vorverstärkerschaltung (26)
zugeordnet ist.
10. Mikrofon nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet dass für jede
Schallöffnung (48) mindestens zwei Membrane (94, 96) vorhanden sind, wovon eine (96)
dazu dient, die Schallöffnung gegenüber der Umgebung zu schützen und die andere Membran
(94) dazu dient, den Schall vor Eintritt in die Schallöffnung (48) zu dämpfen.
1. Microphone comportant un élément formant transducteur piézoélectrique contenu dans
un boîtier, l'élément formant transducteur ayant la forme d'une membrane en matériau
piézoélectrique, caractérisé en ce que la membrane présente au moins deux bras qui
s'en étendent, chaque bras (56, 58) réalisant un chemin électriquement conducteur
respectif conduisant à une partie respective de la membrane, le boîtier comportant
deux parties (30, 32) de boîtier, venant mutuellement en prise, entre lesquelles la
membrane est prise en sandwich au cours de l'assemblage pour diviser le boîtier en
deux chambres distinctes, chaque partie (30, 32) du boîtier présentant un ou plusieurs
évents acoustiques (48) pour admettre le son dans l'une respective des chambres, les
parties (30, 32) du boîtier étant conçues de façon que brsqu'elles sont assemblées
ensemble, le boîtier résultant définit à l'intérieur de sa structure au moins deux
canaux de guidage dont chacun est conçu pour recevoir l'un, respectif, des bras (56,
58) qui s'étendent depuis la membrane.
2. Microphone selon la revendication 1, caractérisé en ce que deux évents acoustiques
(48) sont prévus dans chaque partie (30, 32) de boitier, les deux évents acoustiques
(48) étant disposés en face l'un de l'autre de façon que, une fois assemblé, le boîtier
complet puisse faire partie d'un microphone à gradient de pression du second ordre.
3. Microphone selon la revendication 1 ou 2, caractérisé en ce que chacune des parties
(30, 32) du boîtier qui viennent en prise mutuellement sont prévues avec des caractéristiques
identiques.
4. Microphone selon l'une quelconque des revendications 1 à 3, caractérisé en ce que
chaque partie (30, 32) est fabriquée en un matériau plastique par le procédé de moulage
par injection.
5. Microphone selon la revendication 4, caractérisé en ce que le matériau a un coefficient
de dilatation linéaire qui se trouve sensiblement sur la plage allant de 110 à 120
x 10-61("1.
6. Microphone selon l'une quelconque des revendications 1 à 5, caractérisé en ce que
chaque partie (30, 32) du boîtier présente une ouverture (34) qui s'étend à travers
son centre, chacune des deux parois latérales longitudinales de la partie (30, 32)
du boîtier présentant une portion (36, 38) formant rainure allongée respective, deux
autres parois latérales longitudinales (37, 39) de la partie (30, 32) du boîtier portant
chacune un bras respectif (40, 42) complémentaire de la portion formant rainure (36,
38), permettant ainsi d'assembler ensemble les deux parties de boîtier (30, 32) en
faisant coulisser les bras (40, 42) de l'une des parties de boîtier (30, 32) dans
les portions formant rainure complémentaire (36, 38) de l'autre partie de boîtier
(30, 32).
7. Microphone selon la revendication 6, caractérisé en ce que l'ouverture qui s'étend
à travers le centre de la partie de boîtier (30, 32) est de forme sensiblement cylindrique.
8. Microphone selon la revendication 6 ou 7, caractérisé en ce que chaque bras (40,
42) de la partie (30, 32) de boîtier présente un canal respectif (44, 46) formé sur
sa surface qui fait face vers l'intérieur, ce par quoi, après assemblage des deux
parties de boîtier (30, 32) pour donner le boîtier assemblé, le boîtier assemblé définit,
à l'intérieur des deux parois latérales, les deux canaux de guidage pour recevoir
les deux bras (56, 58) qui s'étendent depuis la membrane.
9. Microphone selon la revendication 8, caractérisé en ce qu'il est prévu deux contacts
électriques (60), chaque contact (60) présentant une portion conçue pour être reçue
dans le canal de guidage et présentant une portion d'extrémité courbe (25) pour venir,
à l'intérieur du canal de guidage, buter contre une surface électriquement conductrice
de l'un des bras (56, 58) qui s'étendent depuis la membrane, la surface électriquement
conductrice formant un chemin électrique jusqu'à une électrode métallisée prévue sur
une surface de la membrane, chaque contact électrique présentant aussi une extrémité
formant borne (23) conçue pour s'étendre hors du canal de guidage et se connecter
dans une fiche femelle associée à un circuit préamplificateur (26).
10. Microphone selon l'une quelconque des revendications 1 à 9, caractérisé en ce
qu'au moins deux membranes (94, 96) sont prévues pour chaque évent acoustique (48),
l'une des membranes (96) servant à protéger rêvent acoustique à l'égard de l'environnement
et l'autre membrane (94) servant à amortir le son avant son entrée dans l'évent acoustique
(48).