U.S. patent application number 14/920849 was filed with the patent office on 2016-02-11 for microphone module with sound pipe.
The applicant listed for this patent is Invensense, Inc.. Invention is credited to Alain V. Guery, Kieran P. Harney, Brian Moss, Dipak Sengupta.
Application Number | 20160044409 14/920849 |
Document ID | / |
Family ID | 47326302 |
Filed Date | 2016-02-11 |
United States Patent
Application |
20160044409 |
Kind Code |
A1 |
Harney; Kieran P. ; et
al. |
February 11, 2016 |
MICROPHONE MODULE WITH SOUND PIPE
Abstract
A microphone module has a substrate with an aperture to allow
sound waves to pass through the substrate, a lid mounted to the
substrate to define a first interior volume, a microphone mounted
to the substrate within the first interior volume, and a housing
coupled to the substrate and covering the aperture. The housing
forms a second interior volume and includes an acoustic port
configured to allow sound to enter the second interior volume. The
module further includes a pipe extending from the acoustic port in
the housing, and at least one exterior interface pad outside of the
second interior volume. The pipe has an open end to receive sound
waves and direct them toward the acoustic port in the housing.
Moreover, the at least one exterior interface pad electrically
couples to the microphone.
Inventors: |
Harney; Kieran P.; (Andover,
MA) ; Sengupta; Dipak; (Boxboro, MA) ; Moss;
Brian; (Skehacreggaun, IE) ; Guery; Alain V.;
(Andover, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Invensense, Inc. |
San Jose |
CA |
US |
|
|
Family ID: |
47326302 |
Appl. No.: |
14/920849 |
Filed: |
October 22, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14223996 |
Mar 24, 2014 |
9173015 |
|
|
14920849 |
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|
13661402 |
Oct 26, 2012 |
8747280 |
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14223996 |
|
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|
61561121 |
Nov 17, 2011 |
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Current U.S.
Class: |
381/338 |
Current CPC
Class: |
H01L 2224/48137
20130101; H01L 2224/48091 20130101; H01L 2924/15151 20130101; H01L
2224/48091 20130101; H04R 1/04 20130101; H04R 1/08 20130101; H04R
19/005 20130101; H04R 2201/003 20130101; H04R 19/04 20130101; H04R
1/342 20130101; H04R 2499/11 20130101; H01L 2924/00014
20130101 |
International
Class: |
H04R 1/34 20060101
H04R001/34; H04R 19/04 20060101 H04R019/04; H04R 19/00 20060101
H04R019/00; H04R 1/04 20060101 H04R001/04 |
Claims
1. A microphone module comprising: a substrate having a first side,
and a second side opposite the first side, the substrate having an
aperture extending from the first side to the second side to allow
sound waves to pass through the substrate; a lid mounted to the
first side, the first side and lid defining a first interior
volume, the aperture configured to allow sound to enter the first
interior volume; a microphone mounted to the first side and within
the first interior volume; a sound pipe having an open end to
receive sound waves and direct the sound waves toward the aperture;
and at least one exterior interface pad on the second side and
electrically coupled to the microphone.
2. The microphone module of claim 1, further including a housing
including the sound pipe, the sound pipe having a pipe volume, the
pipe volume forming most of a second interior volume, the sound
pipe being mounted substantially flush against the second side of
the substrate.
3. The microphone module of claim 2, wherein the housing and at
least a portion of the second side of the substrate comprise a pipe
volume.
4. The microphone module of claim 3, wherein the housing being
coupled to the second side and covering the aperture, the housing
and second side forming a second interior volume, the housing
including an acoustic port configured to allow sound to enter the
second interior volume, the housing covering no more than a portion
of the second side of the substrate.
5. The microphone module of claim 1, wherein the sound pipe is
straight.
6. The microphone module of claim 1, further including a bend
configured to allow the sound pipe to run from the microphone
module to a distal sound source.
7. The microphone module of claim 1, further including a flange,
the sound pipe extending from the flange, the flange resting
substantially flush against the second side of the substrate.
8. A microphone module comprising: a substrate having a first side,
and a second side opposite the first side, the substrate having an
aperture extending from the first side to the second side to allow
sound waves to pass through the substrate, the substrate having a
metalized portion; a lid mounted to the first side, the first side
and lid defining a first interior volume, the lid being formed from
a conductive material, the lid being electrically connected to the
metalized portion of the substrate to protect against
electromagnetic interference; a microphone mounted to the first
side and within the first interior volume, the microphone being a
MEMS microphone; a circuit chip coupled with the first side of the
substrate and being electrically connected with the microphone, the
circuit chip being mounted within the first interior volume; a
sound pipe having an open end to receive sound waves and direct the
sound waves toward the aperture; and at least one exterior
interface pad on the second side and outside of the second interior
volume, the at least one exterior interface pad electrically
coupled to the microphone, the at least one exterior interface pad
being solderable.
9. The microphone module of claim 8, further including a housing
including the sound pipe, the sound pipe having a pipe volume, the
pipe volume forming most of a second interior volume, the sound
pipe being mounted substantially flush against the second side of
the substrate.
10. The microphone module of claim 9, wherein the housing and at
least a portion of the second side of the substrate comprise a pipe
volume.
11. The microphone module of claim 10, wherein the housing is
coupled to the second side and covering the aperture and including
an acoustic port configured to allow sound to enter the pipe
volume, the housing covering no more than a portion of the second
side of the substrate.
12. The microphone module of claim 8, wherein the sound pipe is
straight.
13. The microphone module of claim 8, further including a bend
configured to allow the sound pipe to run from the microphone
module to a distal sound source.
14. The microphone module of claim 8, further including a flange,
the sound pipe extending from the flange, the flange resting
substantially flush against the second side of the substrate.
Description
PRIORITY
[0001] This patent application is a divisional application of U.S.
patent application Ser. No. 14/223,996, filed on Mar. 24, 2014, and
naming Kieran P Harney, Dipak Sengupta, Brian Moss, and Alain Guery
as inventors, and entitled "MICROPHONE MODULE WITH SOUND PIPE",
which is a divisional application of U.S. patent application Ser.
No. 13/661,402, filed on Oct. 26, 2012, and naming Kieran P Harney,
Dipak Sengupta, Brian Moss, and Alain Guery as inventors, and
entitled "MICROPHONE MODULE WITH SOUND PIPE", which claims priority
from provisional U.S. patent application number 61/561,121, filed
Nov. 17, 2011, entitled, "MICROPHONE MODULE," and naming Kieran P
Harney, Dipak Sengupta, Brian Moss, and Alain Guery as inventors,
the disclosure of which is incorporated herein, in its entirety, by
reference.
FIELD OF THE INVENTION
[0002] The invention generally relates to microphones and, more
particularly, the invention relates to a structure for housing
microphones.
BACKGROUND OF THE INVENTION
[0003] Small microphone systems have a broad range of applications,
including use in hearing aids, Bluetooth headsets, and mobile
phones. Typical microphone systems include a microphone element,
such as a microelectromechanical system microphone (also known as a
"micromachined microphone," "silicon microphone," or "MEMS
microphone"). The microphone may include on-board circuitry to
process the microphone element's electrical output signals, or may
be packaged with another circuit in the same package.
[0004] Many microphone packages have a base and a lid, and are
configured to be mounted onto a larger substrate, such as a printed
circuit board or other surface of a larger system. For example, a
packaged microphone may be mounted to an interior surface of a host
system, such as cellular phone. Placement of the microphone
system/packaged microphone within the host system is important,
however, to ensure that acoustic signals can reach their internal
microphone element. If spaced too far from a host port that
receives those signals (e.g., the mouthpiece of a mobile
telephone), the microphone element may not adequately receive and
convert the input acoustic signal.
SUMMARY OF VARIOUS EMBODIMENTS
[0005] In accordance with one embodiment of the invention, a
microphone module has a substrate with a first side and a second
side opposite the first side. The substrate has an aperture
extending from the first side to the second side to allow sound
waves to pass through the substrate. The module also includes a lid
mounted to the first side to define a first interior volume, a
microphone mounted to the first side and within the first interior
volume, and a housing coupled to the second side and covering the
aperture. The housing and second side form a second interior
volume, while the housing includes an acoustic port configured to
allow sound to enter the second interior volume. The module further
has a pipe extending from the acoustic port in the housing, and at
least one exterior interface pad on the second side and outside of
the second interior volume. The pipe has an open end to receive
sound waves and direct them toward the acoustic port in the
housing. In addition, the at least one exterior interface pad is
electrically coupled to the microphone.
[0006] The housing may have a top and at least one sidewall. The
acoustic port thus may be disposed through the top of the housing,
and the pipe may extend from the top of the housing. Alternatively,
or in addition, the acoustic port may be disposed through the
sidewall of the housing, and the pipe may extend from the at least
one sidewall of the housing. The housing also may include a second
acoustic port with a second pipe extending therefrom. Among other
shapes, the pipe may be straight.
[0007] The microphone may include a MEMS microphone, and the module
further may include a circuit chip coupled with the first side of
the substrate. Moreover, the lid may include conductive material
that is electrically connected with the substrate. For example, the
substrate may have a metalized portion, and the lid may be formed
from metal and be electrically connected to the metalized portion
of the substrate to protect against electromagnetic
interference.
[0008] The housing may take on any of a variety of different
configurations. For example, the housing may include a flanged
sound pipe where the pipe has a pipe volume that forms most of the
second interior volume. In this case, the flanged pipe may be
mounted substantially flush against the second side of the
substrate. Moreover, the housing, which may cover no more than a
portion of the second side, may be formed at least in part from a
conductive material.
[0009] In some embodiments, the microphone covers the aperture in
the substrate. In addition or alternatively, at least one exterior
interface pad preferably is surface mountable. The internal
components may electrically connect with the exterior interface pad
in a number of different manners. For example, the module may have
an interior interface pad within the first interior volume, a
circuit chip within the interior volume, and first and second wire
bonds within the interior volume. The first wire bond may
electrically connect the microphone to the circuit chip, while the
second wire bond may electrically connect the circuit chip to the
interior interface pad. The microphone thus can electrically
connect with the exterior interface pad on the second side through
the first wire bond, circuit chip, second wire bond, and interior
interface pad.
[0010] In accordance with another embodiment of the invention, a
microphone module has a substrate with a first side, and a second
side opposite the first side. The substrate, which has a metalized
portion, also has an aperture extending from the first side to the
second side to allow sound waves to pass through the substrate. The
module further includes a lid mounted to the first side, a MEMS
microphone mounted to the first side and within the first interior
volume, and a circuit chip coupled with the first side of the
substrate and electrically connected with the microphone. The first
side and lid are considered to define a first interior volume, and
the lid is formed from a conductive material. The lid is
electrically connected to the metalized portion of the substrate to
protect against electromagnetic interference. Also, in a manner
similar to the MEMS microphone, the circuit chip also is mounted
within the first interior volume. The module further has a housing
coupled to the second side and covering the aperture. The housing
and second side form a second interior volume, and the housing also
has an acoustic port configured to allow sound to enter the second
interior volume. The housing covers no more than a portion of the
second side of the substrate. A pipe extends from the acoustic port
in the housing. This pipe has an open end to receive sound waves
and direct them toward the acoustic port in the housing. In
addition, the module also has at least one exterior, surface
mountable interface pad on the second side and outside of the
second interior volume. The at least one exterior interface pad
electrically couples to the microphone.
[0011] In accordance with other embodiments of the invention, a
microphone module has a substrate with an aperture to allow sound
waves to pass through the substrate, a lid mounted to the substrate
to define a first interior volume, a microphone mounted to the
substrate within the first interior volume, and a housing coupled
to the substrate and covering the aperture. The housing forms a
second interior volume and includes an acoustic port configured to
allow sound to enter the second interior volume. The module further
includes a pipe extending from the acoustic port in the housing,
and at least one exterior interface pad outside of the second
interior volume. The pipe has an open end to receive sound waves
and direct them toward the acoustic port in the housing. Moreover,
the at least one exterior interface pad electrically couples to the
microphone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Those skilled in the art should more fully appreciate
advantages of various embodiments of the invention from the
following "Description of Illustrative Embodiments," discussed with
reference to the drawings summarized immediately below.
[0013] FIGS. 1A and 1B schematically illustrate a prior art MEMS
microphone;
[0014] FIG. 2 schematically illustrates a prior art packaged
microphone;
[0015] FIG. 3 schematically illustrates a prior art packaged
microphone mounted on a circuit board along with other
components;
[0016] FIGS. 4A and 4B schematically illustrate an embodiment of a
microphone module;
[0017] FIG. 5A-5H schematically illustrate various microphone
module embodiments;
[0018] FIGS. 6A-6D schematically illustrate various microphone
module embodiments;
[0019] FIG. 6E schematically illustrates an embodiment of a flanged
sound pipe;
[0020] FIGS. 7A-7D schematically illustrate various microphone
module embodiments;
[0021] FIG. 8 schematically illustrates an embodiment of a
microphone module;
[0022] FIG. 9 schematically illustrates an embodiment of a
microphone module;
[0023] FIG. 10 schematically illustrates an embodiment of a
microphone module;
[0024] FIG. 11 schematically illustrates an embodiment of a
microphone module;
[0025] FIGS. 12A-12C schematically illustrate an embodiment of a
microphone module;
[0026] FIGS. 13A-13C schematically illustrate an embodiment of a
microphone module;
[0027] FIG. 14 schematically illustrates an embodiment of a
microphone module within a host system;
[0028] FIGS. 15A and 15B schematically illustrate an embodiment of
a microphone module;
[0029] FIGS. 16A and 16B schematically illustrate an embodiment of
a microphone module;
[0030] FIGS. 17A and 17B schematically illustrate an embodiment of
a microphone module;
[0031] FIGS. 18 and 19 schematically illustrate an embodiment of a
microphone module;
[0032] FIGS. 20A-20C schematically illustrate an embodiment of a
microphone module;
[0033] FIG. 20D schematically illustrates an embodiment of a
microphone module;
[0034] FIGS. 21A and 21B schematically illustrate an embodiment of
a microphone module;
[0035] FIGS. 22A and 22B schematically illustrate an embodiment of
a microphone module;
[0036] FIGS. 23A and 23B schematically illustrate an embodiment of
a microphone module;
[0037] FIGS. 24A and 24B schematically illustrate an embodiment of
a microphone module;
[0038] FIGS. 25A and 25B schematically illustrate an embodiment of
a microphone module;
[0039] FIGS. 26A and 26B schematically illustrate an embodiment of
a microphone module;
[0040] FIG. 27 schematically illustrates an embodiment of a
microphone module;
[0041] FIG. 28 schematically illustrates an embodiment of a
microphone module;
[0042] FIG. 29 schematically illustrates an embodiment of a
microphone module;
[0043] FIG. 30 schematically illustrates an embodiment of a
microphone module;
[0044] FIG. 31 schematically illustrates an embodiment of a
microphone module;
[0045] FIGS. 32A-32E schematically illustrate ways by which a sound
pipe may interface to a microphone module.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0046] Various microphone module embodiments may be mounted into a
host system in a variety of ways, consequently providing to a
system designer flexibility and options not available with prior
art microphone packages. To that end, in various embodiments, the
microphone module has at least one acoustic port that is
acoustically coupled to a microphone element within its interior.
In some embodiments, the acoustic port includes a structure that is
configured to couple to a sound pipe (or acoustic waveguide) which
may be used as-is, or which may be extended by attaching an
additional length of sound pipe. The sound pipe guides incoming
sound to the acoustic port. As such, the microphone module may be
mounted within a larger system without requiring that its aperture
be immediately adjacent to the sound source, or directly adjacent
to a structure with an aligned counterpart aperture. In fact,
unlike various prior art microphone packages known to the
inventors, some embodiments may not need to be mounted to an
underlying substrate.
[0047] A microphone (or "microphone element") is a transducer that
produces electrical signals in response to impinging sound waves.
The operation of the microphone depends on the ability of sound
waves to reach the microphone, and particularly the microphone's
diaphragm, from the source of the sound. One type of microphone is
a microelectromechanical system (or "MEMS") microphone 100 (a/k/a
"micromachined"), is schematically illustrated in perspective view
in FIG. 1A, while FIG. 1B schematically illustrates a cross-section
of the same microphone 100. Microphone 100 includes a diaphragm 101
suspended by springs 102 above a backplate 104. The diaphragm 101
and backplate 104 are both conductive, and are electrically
isolated from each other. As such, the diaphragm 101 and backplate
104 form a capacitor. It should be noted, however, that MEMS
microphones can be configured in many different ways, and FIG. 1 is
simply one particular way.
[0048] More specifically in the microphone 100, the diaphragm 101
and backplate 104 form a variable capacitor. In operation, the
diaphragm 101 vibrates in response to incident sound waves, thus
changing the gap 105 between the diaphragm 101 and backplate 105.
Among other things, this means that, as the gap 105 narrows, the
diaphragm 101 approaches the backplate 104. The capacitance of the
variable capacitor formed by the diaphragm 101 and backplate 104
therefore varies with the impinging sound waves. The variable
capacitance can be electronically processed to produce an
electrical signal representing the impinging sound waves, in ways
well known in the art.
[0049] Prior art packages known to the inventors typically enclose
the microphone element (e.g., microphone 100) in a package having a
substrate and a lid, as schematically illustrated in FIG. 2. In
that figure, a packaged microphone 200 has a microphone 203 mounted
to a surface 201A of laminate substrate 201. The lid 202 and the
surface 201A of the substrate 201 define an interior volume
surrounding the microphone 203. The microphone 203 is physically
coupled to the substrate 201, and also electrically coupled to the
substrate 201 by one or more wirebonds 204.
[0050] The substrate 201 includes an aperture 205 that permits
sound waves into the interior volume containing the microphone 203.
Some embodiments may alternately, or in addition, have an aperture
in the lid.
[0051] The packaged microphone 200 may be mounted to printed
circuit board 300, which often also includes other circuit elements
201, as schematically illustrated in FIG. 3. Alternatively, the
packaged microphone 200 may be mounted to another surface within a
system that hosts the microphone system 200. Incoming sound waves
reach the microphone 203 by passing through an aperture 302 in the
printed circuit board, and then through the aperture 205 in the
substrate 201. As shown by FIG. 3, this particular example of a
prior art packaging system 200 limits the system designer's freedom
of choice because the packaged system 200 must be mounted adjacent
to (and in fact covering) the aperture 302 in the printed circuit
board.
[0052] In contrast, FIG. 4A schematically shows one embodiment of a
microphone module 400 that provides a wider range of options for
use in a host system. In particular, the microphone module 400
includes an acoustic port 412 to guide sound waves from a distal
location to an interior volume of the system 400. To that end, the
microphone module 400 includes a substrate 401 supporting a
microphone 403, a lid 406 covering the microphone 403, and a
housing 410. In this embodiment, the housing 410 includes two
acoustic ports 412 configured to acoustically couple the entire
microphone module 400 to a source of incoming sound.
[0053] While some embodiments of an acoustic port include a short
section of sound pipe 413, which may be configured to attach to
another section of sound pipe 413, in other embodiments the
acoustic port 412 is an aperture. The sound pipe typically has an
open end to receive and acoustic signal, and an end attached to the
acoustic port 412 in the housing 410. The dimensions of the sound
pipe may be defined, at least in part, by the mechanical and
acoustic characteristics of the host system with which the
microphone system will be used. Among other things, the length and
diameter of the sound pipe can define acoustic performance, such as
resonances that may in some cases be desirable. As just one
example, in some embodiments, the sound pipe may have a circular
cross-section with a diameter of 0.5 millimeters, and be five
millimeters in length. The sound pipe may be straight, or may
include one or more curves, angles or bends.
[0054] Specifically, the module 400 has a substrate 401 having a
first side 401A and a second side 401B. The substrate 401 may be a
laminate (e.g., BT), or other material (e.g., FR-4, a pre-molded
leadframe package base, or a ceramic carrier), and may include
conductive elements to provide ground, power, and/or other
electrical interconnection for other components of the microphone
module 400. As another example, the substrate 401 acts as part of a
Faraday Cage to provide electromagnetically shield its internally
mounted microphone 403.
[0055] The substrate 401 includes at least one aperture 402
extending between the first side 401A and second side 401B. The
microphone 403 and an circuit chip/ASIC 404 are mounted to the
first side, and the microphone 403 preferably straddles/covers the
aperture 402. Some embodiments, however, do not require the
microphone 403 to cover the aperture 402. For example, the
microphone 403 may be adjacent to but not cover the aperture
402.
[0056] The ASIC 404 is electrically coupled to the microphone 403
and processes the output of the microphone 403. The output of the
ASIC, in turn, is coupled to one or more exterior interface pads
405 on the first side 401A. The interface pads 405 may be coupled
to a host system of which the microphone module 400 is a part. The
host system may communicate with the ASIC 404 and/or the microphone
403 via the interface pads 405. Another view of the interface pads
405 on the first surface 401A is schematically illustrated in FIG.
4B.
[0057] A lid 406 is mounted to the first surface 401 and covers the
microphone 403, ASIC 404, and aperture 402. Thus, the substrate 401
and lid 406 form a first interior volume 407, which forms the
majority of the back-volume for the microphone. The lid 406 may be
formed from a variety of materials, and may be a conductor or an
insulator. For example, the lid may be a conductive metal lid
(e.g., a solid metal lid), a plastic lid, a laminate, or a
non-metal lid with conductive plating.
[0058] In some embodiments, some or all of the first surface 401A
of the substrate 401 may be metallized so that the lid may be
coupled to the metallized portion. This may serve to keep the lid
406 grounded, and may serve to protect the microphone 403 or ASIC
404 against external electromagnetic interference ("EMI"). To that
end, a solder or adhesive (e.g., a conductive epoxy) may secure the
lid 406 to some part of the metalized portion of the substrate
401.
[0059] In the embodiment of FIG. 4A, the lid 406 does not cover the
entire first surface 401A, and the interface pads 405 are outside
of the lid 406. In other words, the interface pads 405 are outside
of the first volume 407. This leaves the interface pads 405
available for connecting to a host system, for example by wire
bonds, soldered leads, surface mounting to a printed circuit board
("PCB"), ACF attach (i.e., attachment using an "Anisotropic
Conductive Film"), epoxy attach or other electrical connection
means known in the art. Accordingly, among other things, the pads
405 are considered to be solderable.
[0060] The other side 401B of the substrate 401 includes a housing
410, which covers the aperture 402. The housing may include a
variety of material, and may be a conductor or an insulator. For
example, the housing may be a solid conductive metal structure, a
plastic structure, or a non-metal structure with conductive
plating. The housing 410 may be of the same material as the lid
406, although that is not required.
[0061] In some embodiments, some or all of the second surface 401B
of the substrate 401 may be metallized, so that the housing may be
coupled to the metallized portion. This may keep the housing 410
grounded, and may protect the microphone 403 or ASIC 404 against
external electromagnetic interference. The housing 410 may be
coupled to a metalized portion of the substrate 401 by solder or an
adhesive, such as a conductive epoxy.
[0062] The housing 410 may cover the more of, or less than, the
substrate's surface area than the lid 406. In some embodiments,
however, the housing 410 covers about the same surface area as that
of the lid 406. The substrate 401 and housing 410 form a second
interior volume 411 through which sound can traverse.
[0063] The housing 410 may be considered as having a top 410A
(e.g., the housing surface that is generally parallel with the
substrate 401) and a plurality of sidewalls 410B (e.g., the housing
surface that is generally orthogonal to the substrate 401). The top
410A and sidewalls 410B meet at corners 410C. Of course, other
embodiments may have housings with a variety of shapes, including
rectangular, oval, round, or irregular, and may include shapes with
or without edges and/or corners. An acoustic aperture 412 on a
sidewall 410B is acoustically coupled to the second volume 411, and
may be coupled to a sound pipe 413. The sound pipe 413 guides sound
waves from outside of the module 400 toward and into the second
volume 411. The sound waves then pass through aperture 402 and
impinge on the diaphragm 101 of microphone 403. In some
embodiments, an acoustic port 413 may be on the top wall 410A of
the housing 410, on a sidewall 410B of the housing, or at a corner
410C of the housing. The acoustic port 413 shown in FIG. 4A as
extending from the acoustic aperture 412 on the top wall 410A may
be used in addition to the sound pipe 413 extending from the side
wall 410B, or as an alternative to the sound pipe 413 extending
from the side wall 410B. In other words, the sound pipe 413
extending from the top wall 410A may be the only sound pipe 413
extending from the housing 410.
[0064] In this way, the microphone module 400 may be mounted in a
host system in a location that does not need to be immediately
adjacent to an aperture or the source of the sound, and does not
need to be mounted to a particular surface. Rather, the microphone
module 400 may be mounted in any desired position within the host
system, and the sound pipe can extend from the acoustic aperture
412 to the source of the sound and conduct the sound to the module
400. For example, as shown in FIG. 14, a microphone module 400 may
be mounted at a location 1402 within a cellular telephone 1401.
Alternately, the underlying system/host system could be other
objects, such as a hearing aid, or a Bluetooth headset, to name but
a few. A sound pipe 1403, which in this embodiment is a tube,
directs incoming sound from the mouthpiece 1403 of the cellular
phone 1401 to the microphone module 400. The sound pipe and other
aspects of the microphone system design may be selected and
optimized by the designer of the microphone system, or a host
system, to provide the desired acoustic performance. Alternatively,
rather than using a sound pipe, the system 1400 may have an
aperture to allow sound to enter the microphone.
[0065] An alternate embodiment of a microphone module 500 is
schematically illustrated in FIGS. 5A and 5B. In this embodiment,
interface pads 505 are positioned on the same side of the substrate
501 as the housing 510, and yet are not within the housing 510. As
noted above, this and other embodiments may connect the interface
pads 505 to an underlying system, for example by wire bonds,
soldered leads, surface mounting to a printed circuit board
("PCB"), ACF attach (i.e., attachment using an "Anisotropic
Conductive Film"), epoxy attach or other electrical connection
means known in the art.
[0066] FIG. 5A also shows how the microphone 403 and circuit chip
404 connect with the interface pads 505. Specifically, a first wire
bond 507 connects the microphone 403 to the circuit chip 404, while
a second wire bond 507 connects the circuit chip 404 to an internal
interconnection pad 506. The interior interconnection pad 506 in
turn is electrically connected with the external interface pad 505
through the substrate 401, thus electrically communicating the
interior components (e.g., the microphone 403 and circuit chip 404)
with an underlying system (e.g., the printed circuit board of a
mobile telephone or hearing instrument).
[0067] Yet other embodiments are schematically illustrated in FIGS.
5C-5H. These and other embodiments can have features that can be
combined. The embodiment in FIGS. 5C and 5D includes two arrays of
interface pads, 505A and 505B, on the substrate 510 on either side
of housing 511. In this illustration, the sound pipe 512 extends
from the housing 510 in a direction normal to the page, and along a
line that passes between the interface pad arrays 505A and 505B.
Another embodiment, schematically illustrated in FIGS. 5E and 5F,
has arrays of interface pads 505C and 505D on the same side of the
substrate 520 as the lid 521, microphone 403 and ASIC 507, and on
opposite sides of the lid 521. Other embodiments may have one or
more interface pads 505, or arrays of interface pads 505, with some
on one side of the substrate, and some on the other side of the
substrate.
[0068] Yet another embodiment is schematically illustrated in FIGS.
5G and 5H. In this embodiment, the microphone element 530 and ASIC
531 are on opposite sides of the substrate 532, with an interface
pad array 505E on the same side of the substrate 532 as the
microphone element 530. Related embodiments could include an
interface pad array 505 on the side opposite the microphone element
530.
[0069] An alternate embodiment is schematically illustrated as
microphone module 600 in FIGS. 6A-6D. This embodiment 600 includes
a flanged sound pipe 601 rather than a housing 510/410/etc. (i.e.,
another type of housing). As discussed below with regard to FIG.
6E, the flanged sound pipe 601 has a flange 602, and a sound pipe
603 extending from the flange 602. Other components of the
microphone module 600 are similar to microphone module 400 in FIGS.
4A-4B, including a substrate 401, lid 406, microphone element 403,
ASIC 404 and interface pads 405. Of course, the flanged sound pipe
601 also can be used with the embodiments discussed with regard to
FIGS. 5A-5H. In that case, like the embodiment of FIG. 4A-4B, the
flanged sound pipe 601 is used in place of the housing 510.
[0070] Unlike the comparable portion of the housing 401, however,
the flange 602 does not define an appreciable second volume with
the substrate 401 (i.e., it forms only a very small second volume
or no second volume--if the second volume does not include the
volume of the sound pipe 603). Instead, the flange 602 of flanged
sound pipe 601 rests substantially flush against the substrate 401
such that the sound pipe 603 is adjacent to and in acoustic
communication with the aperture 402. In this way, the sound pipe
603 guides sound from its distal end 604 to the microphone 403.
[0071] This embodiment the sound pipe also includes a bend 605. The
bend 605 provides additional flexibility to a system designer by
allowing the sound pipe to run from the microphone module 600 to a
distal sound source without requiring the sound pipe 601 to follow
a straight line path. The flange can be attached to the substrate
using many different techniques know in the art, including
soldering, conductive or non-conductive adhesives, or other fixing
methods. Alternatively, the sound pipe could have no flange and be
attached directly to the substrate using known methods. Of course,
rather than have a bend, the sound pipe could be straight, as in
sound pipe 621 in the microphone module 620 in FIG. 6C.
[0072] An embodiment of a flanged sound pipe 651 is schematically
illustrated by a perspective view in FIG. 6E, and includes flange
652 and sound pipe 653. The flange 652 in this embodiment is
generally planar, and is configured to mount to a face of a housing
or substrate, or other planar surface. The flange 652 is square,
and is generally normal to the sound pipe 653. However, in other
embodiments, the flange 652 could take a variety of shapes, and
could be angled with respect to the sound pipe 653.
[0073] The sound pipe 653 in this embodiment has a cross-section
that is circular, and flares slightly where it meets the flange
652. However, the shape of the cross-section could also be
described by another conic section, or be rectangular, to name just
a few examples.
[0074] Another embodiment of a microphone module 700 is
schematically illustrated in FIGS. 7A and 7B. The embodiment 700
has a flanged sound pipe 701, and is otherwise similar to the
embodiments in FIGS. 5A-5H.
[0075] A similar embedment 720 is schematically illustrated in
FIGS. 7C and 7D, except that the sound pipe 720 is straight,
similar to the sound pipe 620 in FIG. 6C. FIG. 7C shows sound pipe
721 in cross-section profile, and reveals that the cross-section is
rectangular. However, the cross-section of a sound pipe, in a plane
normal to its length, can take any shape, including square,
rectangular, conic-section, or any other shape. For example, FIG.
6E schematically illustrates a perspective view of a flanged sound
pipe 601 having a flange 602 and a sound pipe 603 with a circular
cross-section.
[0076] Some embodiments have more than one acoustic aperture. One
such embodiment is schematically illustrated as microphone module
800 in FIG. 8. In this embodiment, the lid 806 and the housing 810
each have an acoustic aperture 813 and 820, respectively. The
acoustic apertures 813 and 820 can take the form of sound pipes, or
could also be holes, or a combination of a sound pipe and a hole.
As discussed above, rather than extend from housing side 810B, the
sound pipe 813A can extend from the top side 810A of the housing
810. Moreover, as noted above, this embodiment can have a single
sound pipe/aperture combination rather than two (e.g., just a sound
pipe/aperture combination 813 extending from the housing 810).
[0077] Several embodiments may have multiple lids, housing and
microphones. For example, a dual-module 900 is schematically
illustrated in FIG. 9. The dual module 900 has a single substrate
90 supporting two lids 901A and 901B and two housings 910A and
910B. Each lid 901A and 901B houses a microphone 903A and 903B,
respectively, and an ASIC 904A and 904B respectively. Each
microphone 903A and 904B straddles an aperture, 902A and 902B,
respectively. Each housing 910A and 910B has an acoustic port 913A
and 913B, which are similar to the acoustic ports in
previously-described embodiments. The dual-module 900 has at least
one interface pad 905 that may serve one or both segments of the
dual module. In this embodiment, the interface pad 905 is on the
same side of the substrate as the lids 906A and 906B, but one or
more pads 905 could also be on the other side, but outside the
housing 910B. Some embodiments contain several interface pads 905,
which can be independent (i.e., so that both microphones 903A and
904A are independently electrically accessible). Moreover, some
interface pads 905 may be independent while other interface pads
905 are shared by the two microphones 903A and 904A. Although the
embodiment in FIG. 9 shows two microphones, some embodiments may
have three or more microphones, each with its own lid and housing.
Alternately, some microphone systems may have multiple lids 906,
but only a single corresponding housing 910.
[0078] In an alternate embodiment 1000, two housings 1010A and
1010E are acoustically coupled by a bridge 1020, as schematically
illustrated in FIG. 10. The bridge 1020 allows a single acoustic
aperture or sound pipe 1013 to guide incoming sound signals to both
housings, and ultimately to their associated microphones.
Alternately, the housings 1010A and 1010B, which are connected by
bridge 1020, could be considered to be a single housing. The
dual-module 1000 has at least one interface pad 1005 that serves
both segments of the dual module. In this embodiment, the interface
pad 1005 is on the same side of the substrate as the lids 1006A and
1006B, but one or more pads could also be on the obverse side, but
outside the housing 1010B.
[0079] Yet other dual-module embodiments may also have one or more
acoustic ports 1130A and 1130E in their respective lids 1106A and
1106B, as in dual-module 1100 as schematically illustrated in FIG.
11.
[0080] Other embodiments provide interface pads on a portion
adjacent to a lid. For example, as shown in FIG. 12, a microphone
system 1200 includes a substrate 1201 supporting an ASIC 1202 with
a stacked MEMS microphone 1203 covered by a lid 1204. The substrate
1201 includes an aperture 1205 (which may also be known as a "port
hole") acoustically coupled to an ASIC aperture 1206 in ASIC 1202,
so that sound may pass through the substrate aperture 1206 to reach
microphone 1203. A number of interface pads 1215 reside on the
surface of substrate 1201, on the same side as lid 1204. Other
embodiments, however, may have interface pads on the other side of
the substrate 1201. One or both of the ASIC 1202 and microphone
1203 may be electrically coupled to the interface pads 1215 to
provide an accessible means of electrically communicating with a
host system.
[0081] As with other disclosed embodiments, the interface pads 1215
can be connected by a variety of interconnect means, such as wire
bonds, solder, epoxy or ACF to a printed circuit ("PC") board, or a
laminate, to name but a few. Some embodiments may include an array
of interface pads along an edge of the substrate, such that the
interface pads may be inserted into a socket, such as a linear
socket on a computer's backplane, for example. This embodiment 1200
may be used with a housing and/or a sound pipe (e.g., a flanged
sound pipe) as illustrated in other embodiments herein, but may
also be surface-mounted--for example by interface pads, or by
coupling the substrate 1201 to a surface of a host system.
Therefore, the embodiment 1200 provides a host system designer with
considerable flexibility.
[0082] Various embodiments, including each of the embodiments
described above, may include a filter in one or all of their
substrate apertures, acoustic ports, and/or a sound pipes. One
embodiment 1300 is schematically illustrate in FIGS. 13A-C, in
which a substrate 1301 supports/hosts an ASIC 1302 with a stacked
MEMS microphone 1303 covered by a lid 1304. As with other lids
described above, the lid 1304 may be attached to the substrate 1301
to create a volume that is partially occupied by the ASIC 1302 and
microphone 1303.
[0083] In this embodiment, a filter material resides either within
the aperture 1306, or on a top or bottom face of substrate 1301
covering the aperture. In an embodiment with a laminate substrate,
the filter may be part of a laminate layer, or may be sandwiched
between two laminate layers, for example. Depending on its
construction, the filter 1320 may prevent objects, dust or other
particulate matter, light, moisture or other environmental
contaminants from passing through the aperture 1306. Of course, the
filter 1320 permits acoustic signals enter the interior to contact
the microphone 1303.
[0084] A filter may take a variety of forms. For example, the
filter may be a screen, a gauze member, a PTFE filter, a metal
member, or a ceramic member.
[0085] In an embodiment 1500 schematically illustrated in FIGS. 15A
and 15B, the housing 1501 is made of laminate structures, including
one or more sidewalls 1502 and a top 1503. In the embodiment of
FIGS. 15A and 15B, a sound pipe 1504 extends from lid 1505, while
other embodiments include a sound pipe extending from the housing
1501. Further, a number of interface pads 1506 reside on the outer
surface 1507 of the housing 1501. The interface pads 1506 may
connect to the substrate 1510, microphone element 1511, and/or ASIC
15121 through conductors on or in the laminate structures 1502 and
1503.
[0086] Some embodiments include a shell outside of the housing
and/or the lid. For example, the embodiment 1600 schematically
illustrated in FIGS. 16A and 16B includes a shell 1601 outside of
(or surrounding) lid 1602. A number of interface pads 1603 reside
on the outer surface 1604 of the shell 1601, and may connect to the
substrate 1610, microphone element 1612, or ASIC 1611 through
conductors on or in the laminate structures. The lid 1602 lends
structural support to the shell 1601, and may also provide
electromagnetic shielding to the microphone system 1600. At the
same time, the shell 1601 provides interface pads on the
housing-side of the microphone system. Similarly, another
embodiment 1700 (FIGS. 17A and 17B) includes a shell 1701 outside
of (or surrounding) lid 1702.
[0087] Another embodiment 1800 is schematically illustrated in
FIGS. 18 and 19. In this embodiment, a substrate 1801 has a
microphone 1802 and an ASIC 1803 on one surface 1801A. A lid 1804
is also coupled to the surface 1801A, and covers the microphone
1802 and ASIC 1803, and also spans an aperture 1806 through the
substrate 1801. A shell 1805 is coupled to the surface 1801A, and
includes interface pads 1807. The embodiment 1800 does not include
a housing with a large volume on the side opposite surface 1801A.
However, some embodiments, such as the one schematically
illustrated in FIG. 18, do include a flanged sound pipe 1808 (i.e.,
another type of housing) interfaced with the aperture 1806. It is
note that the inclusion of a shell, such as the shells discussed
above, do not require a housing or a flanged sound pipe 1808, even
though the examples discussed above include such features.
[0088] As noted above, some embodiments include a filter, such as
the embodiment having reference number 2000 and schematically
illustrated in FIGS. 20A-C. More specifically, this embodiment
includes a filter 2001 covering an aperture 2002 in substrate 2003.
In this embodiment, the filter (or "filter material") 2001 is on
the surface 2003A of substrate 2003, which is the side of substrate
2003 opposite to the side that hosts/supports an ASIC 2004 and
microphone element 2005. In other embodiments, however, a filter or
filter material (or additional filter or filter materials) could be
within the aperture 2002, or between the substrate 2003 and ASIC
2004.
[0089] The filter 2001 may also have acoustic properties that delay
the travel of a sound signal. Inclusion of such a filter in a
microphone system may be desirable in a system that has multiple
microphone elements, for example, to adjust the receipt time of a
signal by one microphone element with respect to the receipt of the
signal by another microphone element. Alternately, a filter may
enhance or accentuate the directional sensitivity of a directional
microphone in which a sound signal reaches a microphone element via
two paths between the source of the sound signal and the microphone
element, where at least one of the paths includes a filter that
delays propagation of the sound signal.
[0090] Another embodiment 2050 having one or more filters 2001 is
schematically illustrated in FIG. 20D. This embodiment is similar
to the microphone system 400 of FIG. 4, and some reference numbers
from that embodiment are re-used in FIG. 20D. This embodiment of a
microphone system 2050 shows two filters, 2051 and 2052, although
the system may alternately be configured with only one filter.
Filter 2151 occupies a portion of sound pipe 413, or could be
coupled to the inner surface of the housing 410 covering the pipe
aperture, while filter 2152 straddles aperture 402 in substrate
401, on surface 401B. In addition to introducing an acoustic delay,
the one or more filters may serve a more traditional filtering
purpose, such as blocking moisture, dust and other particulate
matter or other contaminants, from entering the microphone system
2050, or from passing through the aperture 402, for example. As in
various embodiments, the sound pipe can alternatively be an
aperture.
[0091] Some embodiments include multiple microphone packages
associated with a single acoustic port module. For example, an
acoustic port module 2101 is schematically illustrated in an
embodiment 2100 in FIG. 21. The acoustic port module 2101 in this
embodiment includes an enclosed volume 2102, and a sound pipe 2103.
The acoustic port module 2101 may be metal, plastic, or ceramic, or
other material. In some embodiments, the acoustic port module 2101
may include printed circuit board having conductors and/or
interface pads to electrically couple microphone circuits to a host
system.
[0092] An external acoustic signal may enter the enclosed volume
2102 via the sound pipe 2103, and pass through to two microphone
elements 2104 and 2105 via two apertures 2106 and 2107,
respectively. In this way, each microphone element 2104 and 2105
has the benefit of sharing a common sound pipe 2103 owing to the
common acoustic port module 2101. Such an arrangement may make the
microphone system 2100 more compact than systems in which each
microphone element has its own housing. In some embodiments,
exposing the microphone elements 2104 and 2105 to a common sound
pipe (in other words, to a common acoustic port) may facilitate
allowing the incoming sound to reach the microphone elements 2104
and 2105 at the same time, or with a determinable phase or time
differential.
[0093] The microphone system 2100 also includes coupling elements
2110 and 2111. Coupling element 2110 has a tube portion 2112 and a
flange portion 2113. Tube portion 2112 passes through apertures
2106, while flange portion 2113 is outside of acoustic port module
2101. The flange portion 2113 couples to microphone package 2114
such that the tube portion 2112 is acoustically coupled to an
aperture 2114A in package 2114. In other words, the tube portion
2112 and package aperture 2114A form a hole between internal volume
2102 and the interior of the microphone package 2114. The flange
portion 2113 provides a planar surface to meet the outer surface of
package 2114. The interface between the flange portion 2113 and the
package 2114 provides a structural interface, and in some
embodiments may create a seal between the acoustic port module 2101
and the package 2114.
[0094] A ball-grid-array mountable embodiment of a microphone
system 2200 is schematically illustrated in FIGS. 22A and 22B. A
housing 2201 is coupled to substrate 2202. The housing 2201
includes a sound pipe 2203 that passes between solder balls 2204 on
a surface of the substrate 2202. The diameter of the solder balls
2204 exceeds the height of the housing 2201, so that the solder
balls 2204 may mount to a surface without physical interference
from the housing 2201. Such an arrangement allows the microphone
system 2200 to have electrical communication with a host system via
solder balls 2204, rather than (or in addition to) including
interface pads on the housing 2201, for example.
[0095] Some embodiments may include more than one ball-grid-array
mountable device. For example, the microphone system 2300
schematically illustrated in FIGS. 23A and 23B includes two such
devices, each of which is similar to the embodiment in FIGS. 22A
and 22B. Each housing 2301 and 2311 includes a sound pipe 2302 and
2312, respectively, although the two sound pipes 2302 and 2312 need
not extend in the same direction. In some embodiments, the sound
pipes 2302 and 2312 extend in different directions (e.g., at 90
degree angles to one another, for example) to provide the system
2300 with access to sounds from different directions, or to a
single sound source from multiple angles.
[0096] Some embodiments provide a double-chambered package. Package
2400, as schematically illustrated in FIGS. 24A and 24B, includes a
microphone chamber 2401, which houses a microphone 2410, and a
backchamber 2402. The backchamber 2402, which may also be thought
of as a housing, includes a sound pipe 2420 to allow entry of
acoustic energy. The package 2400 may be a molded member, or a
combination of one or more members 2401A and 2401B. The package
2400 may be of a variety of materials, such as metal, ceramic, or
metallized polymer, for example. An outer surface of the
backchamber 2402 includes one or more interface pads 2404 for
connecting the package 2400 to a host system.
[0097] An aperture 2406 opens the microphone chamber 2401 to the
environment outside of the package 2400 to allow sound to enter the
microphone chamber 2401. An aperture 2403 acoustically couples the
microphone chamber 2401 to the backchamber 2402.
[0098] Another embodiment schematically illustrated in FIGS. 25A
and 25B places interface pads 2504 on a surface 2501A of the
package 2500 outside of the microphone chamber 2501. The
backchamber 2502, which may also be thought of as a housing,
includes a sound pipe 2520 to allow entry of acoustic energy.
[0099] An embodiment of a multiple microphone system 2600 is
schematically illustrated in FIGS. 26A and 26B. A microphone 2601
is within a microphone chamber 2602. The chamber 2602 is
acoustically coupled to a housing 2603 via an aperture 2604 and a
coupling element 2605, similar to the coupling elements described
above. A second microphone chamber 2610 and second housing 2611 are
coupled to the first housing 2603 by solder balls 2606. Each of the
housings 2603 and 2611 have a sound pipes 2620A and 2620B,
respectively, extending outwardly to allow external sound signals
to enter the housing and reach the microphones 2601 and 2613. The
bottom housing 2611 also includes an array of interface pads
2615.
[0100] In addition to the embodiments described above, there are a
variety of other ways to connect a sound pipe to a microphone
system. For example, FIG. 27 schematically illustrates a microphone
package 2700 having a base 2701 and lid 2702 mounted on the base
2701. In this embodiment, the base 2701 includes an aperture 2701A,
and supports an ASIC 2703, and a microphone element 2704 straddling
the aperture 2701A.
[0101] The microphone package 2700, in turn, is mounted to a
substrate 2710, which may be part of a host system. In particular,
the aperture 2701A of package 2700 is mounted over an aperture
2710A in the substrate 2710 so that the two apertures provide a
sound path to the microphone element 2704. On the opposite side of
the substrate from the microphone package 2700 is a coupling tube
2720.
[0102] The coupling tube 2720 has a flange portion 2721 and an
adapter portion 2722. The flange portion 2721 may be secured to
substrate 2710 by a variety of means known in the art, such as
epoxy or conductive epoxy, for example, and the adapter portion
2722 extends away from the substrate 2710 to meet a corresponding
sound tube (not shown). The sound tube may couple to the adapter
portion 2722 in a variety of ways. For example, the sound tube may
fit within the opening 2722A of the adapter portion, or the adapter
portion 2722 may fit within the sound tube, to name but a few
alternatives.
[0103] The embodiment schematically illustrated in FIG. 27 also has
a washer 2730 and a membrane filter 2740. The washer 2730 is
coupled directly to the substrate 2710 within the coupling tube
2720, and helps to seal the interface of the coupling tube 2720,
filter 2740, and the substrate 2710. Further, the washer 2730 may
be secured to the substrate 2710, and the filter 2740 may, in turn,
be secured to the washer 2730, so that the filter 2740 and washer
2730 cooperate to secure each other to the substrate and/or even to
the inside of the coupling tube 2720.
[0104] An alternate embodiment shown in FIG. 28 and identified by
reference number 2800 has a filter 2801 within the aperture 2810A
of substrate 2810. This embodiment does not include a washer,
although a washer could be included on the substrate 2810 within
the coupling tube 2822.
[0105] Other embodiments may forgo the filter and washer entirely,
as in embodiment 2900 schematically illustrated in FIG. 29.
[0106] Alternate embodiments include a microphone package formed by
a lid mounted directly to a substrate within a host system. In
other words, the microphone package may forgo a base (e.g., base
2701 in FIG. 27). Such embodiment may still include a filter, such
as filter 3140 in FIG. 31, for example, or a cooperating filter
3040 and washer 3030 as in FIG. 30, for example.
[0107] Several embodiments described herein include a sound pipe
extending from a housing or a lid. Illustrations of such sound
pipes may show the sound pipes as relatively short. However, that
is not necessarily the case. For example, FIG. 14 schematically
illustrates a sound pipe 1404 extending a considerable distance
from the microphone system 400. As another example, FIG. 32A
schematically illustrates a sound pipe 3201A extending far from a
microphone system 3200. In this embodiment, the sound pipe also
includes corners or bends 3210.
[0108] Other embodiments provide a variety of ways to interface an
extended sound tube to a microphone system. For example an
embodiment in FIG. 32B includes a sound pipe 3201B extending a
short distance from microphone system 3200. An extended sound pipe
3202 (which may also be known as a "sound pipe extension") couples
to sound pipe 3201B. In particular, the inside diameter (or inside
dimensions) of sound pipe extension 3202 are greater than the
outside diameter (or outside dimensions) of sound pipe 3201B such
that sound pipe extension 3202 fits over the sound pipe 3201B.
[0109] In an alternate embodiment schematically illustrated in FIG.
32C, the outside diameter (or outside dimensions) of sound pipe
extension 3203 are less than the inside diameter (or inside
dimensions) of sound pipe 3201C such that sound pipe extension 3203
fits within the sound pipe 3201C.
[0110] Yet another embodiment is schematically illustrated in FIG.
32D, in which a sound pipe adapter 3201D extends into the interior
volume of housing 3210. Sound pipe extension 3204 then inserts into
sound pipe adapter 3201D to guide sound into the housing 3210.
[0111] In another embodiment schematically illustrated in FIG. 32E,
a sound pipe could interface directly to aperture 3201E.
[0112] Various embodiments discussed above therefore provide a
system designer with more choices and greater flexibility in
designing the host system, and selecting the shape and size of a
microphone module, and locating and mounting the microphone module
within the host system.
[0113] The embodiments of the invention described above are
intended to be merely exemplary; numerous variations and
modifications will be apparent to those skilled in the art. All
such variations and modifications are intended to be within the
scope of the present invention as defined in any appended
claims.
[0114] Although the above discussion discloses various exemplary
embodiments of the invention, it should be apparent that those
skilled in the art can make various modifications that will achieve
some of the advantages of the invention without departing from the
true scope of the invention.
* * * * *