U.S. patent application number 10/569135 was filed with the patent office on 2006-12-28 for sound absorbing structure body and producing method thereof.
This patent application is currently assigned to KABUSHIKI KAISHA KOBE SEIKO SHO. Invention is credited to Zenzo Yamaguchi.
Application Number | 20060289229 10/569135 |
Document ID | / |
Family ID | 34269780 |
Filed Date | 2006-12-28 |
United States Patent
Application |
20060289229 |
Kind Code |
A1 |
Yamaguchi; Zenzo |
December 28, 2006 |
Sound absorbing structure body and producing method thereof
Abstract
A peak frequency having a high sound absorption coefficient is
enlarged. A sound absorbing structure body comprises a
concave-convex plate, a closure plate, and first and second
partition plates. The concave-convex plate includes a convex
portion and a concave portion (concave-convex portion) and an
opening. The closure plate is bonded to the concave-convex plate so
as to form a hollow portion by closing one of the convex portion
and the concave portion, and the hollow portion is communicated
with an outside space through the opening. The first and second
partition plates have a number of through holes respectively, and
the first and second partition plates partition the hollow portion
into at least two partitioned spaces.
Inventors: |
Yamaguchi; Zenzo; (Hyogo,
JP) |
Correspondence
Address: |
REED SMITH LLP
3110 FAIRVIEW PARK DRIVE, SUITE 1400
FALLS CHURCH
VA
22042
US
|
Assignee: |
KABUSHIKI KAISHA KOBE SEIKO
SHO
Hyogo
JP
|
Family ID: |
34269780 |
Appl. No.: |
10/569135 |
Filed: |
August 31, 2004 |
PCT Filed: |
August 31, 2004 |
PCT NO: |
PCT/JP04/12564 |
371 Date: |
February 22, 2006 |
Current U.S.
Class: |
181/290 ;
181/293 |
Current CPC
Class: |
G10K 11/172
20130101 |
Class at
Publication: |
181/290 ;
181/293 |
International
Class: |
E04B 1/82 20060101
E04B001/82; E04B 2/02 20060101 E04B002/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2003 |
JP |
2003-313869 |
Claims
1. A sound absorbing structure body comprising: a concave-convex
plate which includes a concave-convex portion and an opening; a
closure plate which is bonded to said concave-convex plate so as to
form a hollow portion by closing one of said concave-convex
portion, the hollow portion being communicated with an outside
space through said opening; and a first partition member which
partitions said hollow portion into at least two first partitioned
spaces.
2. The sound absorbing structure body according to claim 1, further
comprising a closure member which closes said opening of an opened
portion in said concave-convex plate, the opened portion whose one
end is opened being adjacent to said hollow portion.
3. The sound absorbing structure body according to claim 1, further
comprising a third partition member which partitions an opened
portion into at least two third partitioned spaces in said
concave-convex plate, the opened portion whose one end is opened
being adjacent to said hollow portion.
4. The sound absorbing structure body according to claim 1, wherein
said first partition member has a porous plate having a number of
through holes.
5. The sound absorbing structure body according to claim 3, wherein
said third partition member has a porous plate having a number of
through holes.
6. The sound absorbing structure body according to claim 1, wherein
said first partition member has foil which is provided vibratably
or rubbably.
7. The sound absorbing structure body according to claim 3, wherein
said third partition member has foil which is provided vibratably
or rubbably.
8. The sound absorbing structure body according to claim 6, wherein
said foil has a number of through holes.
9. The sound absorbing structure body according to claim 7, wherein
said foil has a number of through holes.
10. The sound absorbing structure body according to claim 6,
wherein said foil has a convex-convex portion.
11. The sound absorbing structure body according to claim 7,
wherein said foil has a convex-convex portion.
12. The sound absorbing structure body according to claim 1,
wherein a sound absorbing material is provided in at least one of
said at-least-two first partitioned spaces.
13. The sound absorbing structure body according to claim 3,
wherein a sound absorbing material is provided in at least one of
said at-least-two third partitioned spaces.
14. The sound absorbing structure body according to claim 1,
wherein only one of said at-least-two first partitioned spaces is
communicated with said outside space.
15. The sound absorbing structure body according to claim 3,
wherein only one of said at-least-two third partitioned spaces is
communicated with said outside space.
16. A sound absorbing structure body comprising: an interior member
which includes an opening; an exterior member which is arranged
opposite to said interior member while separated from said interior
member; a coupling member which couples said interior member and
said exterior member to form a hollow portion communicated with an
outside space through said opening; and a second partition member
which partitions said hollow portion into at least two second
partitioned spaces.
17. A sound absorbing structure body according to claim 16, wherein
said interior member is a concave-convex plate having a
concave-convex portion, which is integrated with said coupling
member and formed by the coupling member, and said exterior member
is a closure plate which is bonded so as to close one of said
concave-convex portion.
18. The sound absorbing structure body according to claim 17,
further comprising a closure member which closes said opening of an
opened portion in said concave-convex plate, the opened portion
whose one end is opened being adjacent to said hollow portion.
19. The sound absorbing structure body according to claim 17,
further comprising a third partition member which partitions an
opened portion into at least two third partitioned spaces in said
concave-convex plate, the opened portion whose one end is opened
being adjacent to said hollow portion.
20. The sound absorbing structure body according to claim 16,
wherein said second partition member has a porous plate having a
number of through holes.
21. The sound absorbing structure body according to claim 19,
wherein said third partition member has a porous plate having a
number of through holes.
22. The sound absorbing structure body according to claim 16,
wherein said second partition member has foil which is provided
vibratably or rubbably.
23. The sound absorbing structure body according to claim 19,
wherein said third partition member has foil which is provided
vibratably or rubbably.
24. The sound absorbing structure body according to claim 22,
wherein said foil has a number of through holes.
25. The sound absorbing structure body according to claim 23,
wherein said foil has a number of through holes.
26. The sound absorbing structure body according to claim 22,
wherein said foil has a concave- convex portion.
27. The sound absorbing structure body according to claim 23,
wherein said foil has a concave- convex portion.
28. The sound absorbing structure body according to claim 16,
wherein a sound absorbing material is provided in at least one of
said at-least-two second partitioned spaces.
29. The sound absorbing structure body according to claim 19,
wherein a sound absorbing material is provided in at least one of
said at-least-two third partitioned spaces.
30. The sound absorbing structure body according to claim 16,
wherein only one of said at-least-two second partitioned spaces is
communicated with said outside space.
31. The sound absorbing structure body according to claim 19,
wherein only one of said at-least-two third partitioned spaces is
communicated with said outside space.
32. A method of producing a sound absorbing structure body
comprising a concave-convex plate which includes a concave-convex
portion and an opening; a closure plate which is bonded to said
concave-convex plate so as to form a hollow portion by closing one
of said concave-convex portion, the hollow portion being
communicated with an outside space through said opening; and a
first partition member which partitions said hollow portion into at
least two first partitioned spaces, the sound absorbing structure
body producing method wherein a support hole is formed in said
first partition member, the support hole is inserted into a convex
portion of said concave-convex plate, said support hole is
supported and fixed by said convex portion in the midway of the
insertion, and thereby said first partition member is provided in
said hollow portion.
33. The sound absorbing structure body producing method according
to claim 32, wherein a number of through holes are formed in said
first partition member.
34. A method of producing a sound absorbing structure body
comprising a concave-convex plate which includes a concave-convex
portion and an opening; a closure plate which is bonded to said
concave-convex plate so as to form a hollow portion by closing one
of said concave-convex portion, the hollow portion being
communicated with an outside space through said opening; and a
first partition member which partitions said hollow portion into at
least two first partitioned spaces, the sound absorbing structure
body producing method wherein a fitting convex portion is formed in
said first partition member, the fitting convex portion is fitted
into a convex portion of said concave-convex plate, said fitting
convex portion is supported and fixed by said convex portion in the
midway of the fitting, and thereby said first partition member is
provided in said hollow portion.
35. The sound absorbing structure body producing method according
to claim 34, wherein a number of through holes are formed in said
first partition member.
36. A method of producing a sound absorbing structure body
comprising an interior member which includes an opening; an
exterior member which is arranged opposite to said interior member
while separated from said interior member; a coupling member which
couples said interior member and said exterior member to form a
hollow portion communicated with an outside space through said
opening; and a second partition member which partitions said hollow
portion into at least two second partitioned spaces, said interior
member being a concave-convex plate having a concave-convex
portion, which is integrated with said coupling member and formed
by the coupling member, said exterior member being a closure plate
which is bonded to close one of said concave-convex portion, the
sound absorbing structure body producing method wherein a support
hole is formed in said second partition member, the support hole is
inserted into a convex portion of said concave-convex plate, said
support hole is supported and fixed by said convex portion in the
midway of the insertion, and thereby said second partition member
is provided in said hollow portion.
37. The sound absorbing structure body producing method according
to claim 36, wherein a number of through holes are formed in said
second partition member.
38. A method of producing a sound absorbing structure body
comprising an interior member which includes an opening; an
exterior member which is arranged opposite to said interior member
while separated from said interior member; a coupling member which
couples said interior member and said exterior member to form a
hollow portion communicated with an outside space through said
opening; and a second partition member which partitions said hollow
portion into at least two second partitioned spaces, said interior
member being a concave-convex plate having a concave-convex
portion, which is integrated with said coupling member and formed
by the coupling member, said exterior member being a closure plate
which is bonded to close one of said concave-convex portion, the
sound absorbing structure body producing method wherein a fitting
convex portion is formed in said second partition member, the
fitting convex portion is fitted into a convex portion of said
concave-convex plate, said fitting convex portion is supported and
fixed by said convex portion in the midway of the fitting, and
thereby said second partition member is provided in said hollow
portion.
39. The sound absorbing structure body producing method according
to claim 38, wherein a number of through holes are formed in said
second partition member.
Description
TECHNICAL FIELD
[0001] The present invention relates to a sound absorbing structure
body exerting sound insulation performance against sound pressure
excitation and a method of producing the sound absorbing structure
body. The sound absorbing structure body is suitable for a
structural member, a panel, and a sound insulating cover for an
automobile, a railroad car, a building, a general purpose machine,
and the like.
BACKGROUND ART
[0002] Conventionally, as described in Patent Document 1, there is
known a sound absorbing member for a vehicle in which a perforated
plate thickness, a hole diameter, a hole pitch, and an air layer
thickness are adjusted while a perforated plate is placed on a
lower surface side of a panel through an air layer, and thereby
noises are absorbed in a predetermined frequency domain. According
to the configuration described in Patent Document 1, the noises in
a particular frequency can effectively be absorbed by utilizing the
Helmholtz Resonance Principle to adjust the perforated plate
thickness, the hole diameter, the hole pitch, and the air layer
thickness.
[0003] Patent Document 1: Japanese Patent Laid-Open No. Hei
6-298014
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0004] However, in the conventional configuration, a sound
absorption coefficient is increased only near the Helmholtz
resonance frequency, and there is a problem that sound absorbing
performance is difficult to broaden.
Means for Solving the Problems
[0005] A first invention has a configuration comprising a
concave-convex plate which includes a concave-convex portion and an
opening; a closure plate which is bonded to the concave-convex
plate so as to form a hollow portion by closing one of the
concave-convex portion, the hollow portion being communicated with
an outside space through the opening; and a first partition member
which partitions the hollow portion into at least two first
partitioned spaces. According to the configuration of the first
invention, the excellent sound absorbing performance in which the
frequency band having the high sound absorption coefficient is
enlarged can be obtained.
[0006] In the concave-convex plate of the first invention, a second
invention has a configuration further comprising a closure member
which closes the opening of an opened portion in the concave-convex
plate, the opened portion whose one end is opened being adjacent to
the hollow portion. In the concave-convex plate of the first
invention, a third invention has a configuration further comprising
a third partition member which partitions an opened portion into at
least two third partitioned spaces in the concave-convex plate, the
opened portion whose one end is opened being adjacent to the hollow
portion. According to the configurations of the second and third
inventions, the further high sound absorption coefficient can be
obtained.
[0007] A fourth invention has a configuration in which the first
partition member has a porous plate having a number of through
holes. A fifth invention has a configuration in which the third
partition member has a porous plate having a number of through
holes. According to the configurations of the fourth and fifth
inventions, the excellent sound absorbing performance in which the
frequency band having the high sound absorption coefficient is
enlarged can be obtained. A sixth invention has a configuration in
which the first partition member has foil which is provided
vibratably or rubbably, and a seventh invention has a configuration
in which the third partition member has foil which is provided
vibratably or rubbably. In this case, the foil of the sixth
invention may have a number of through holes (eighth invention),
and the foil of the seventh invention may have a number of through
holes (ninth invention). The foil of the sixth invention may have a
convex-convex portion (tenth invention), and the foil of the
seventh invention may have a convex-convex portion (eleventh
invention).
[0008] In the first invention, a twelfth invention has a
configuration in which a sound absorbing material is provided in at
least one of the at-least-two first partitioned spaces. In the
third invention, a thirteenth invention has a configuration in
which a sound absorbing material is provided in at least one of the
at-least-two third partitioned spaces. According to the
configurations of the twelfth and thirteenth inventions, the
excellent sound absorbing performance in which the frequency band
having the high sound absorption coefficient is enlarged can be
obtained.
[0009] In the first invention, a fourteenth invention has a
configuration in which only one of the at-least-two first
partitioned spaces is communicated with the outside space. In the
third invention, a fifteenth invention has a configuration in which
only one of the at-least-two third partitioned spaces is
communicated with the outside space. According to the fourteenth
and fifteenth inventions, the configuration is simplified.
[0010] A sixteenth invention has a configuration comprising an
interior member which includes an opening; an exterior member which
is arranged opposite to the interior member while separated from
the interior member; a coupling member which couples the interior
member and the exterior member to form a hollow portion
communicated with an outside space through the opening; and a
second partition member which partitions the hollow portion into at
least two second partitioned spaces. According to the configuration
of the sixteenth invention, the excellent sound absorbing
performance in which the frequency band having the high sound
absorption coefficient is enlarged can be obtained.
[0011] A seventeenth invention is characterized in that the
interior member is a concave-convex plate having a concave-convex
portion, which is integrated with the coupling member and formed by
the coupling member, and the exterior member is a closure plate
which is bonded so as to close one of the concave-convex portion.
According to the configuration of the seventeenth invention, the
sound absorbing structure body can easily be produced by
integrating the interior member and the coupling member.
[0012] In the concave-convex plate of the seventeenth invention, an
eighteenth invention has a configuration further comprising a
closure member which closes the opening of an opened portion in the
concave-convex plate, the opened portion whose one end is opened
being adjacent to the hollow portion. In the concave-convex plate
of the seventeenth invention, a nineteenth invention has a
configuration further comprising a third partition member which
partitions an opened portion into at least two third partitioned
spaces in the concave-convex plate, the opened portion whose one
end is opened being adjacent to the hollow portion. According to
the configurations of the eighteenth and nineteenth inventions, the
further high sound absorption coefficient can be obtained.
[0013] A twentieth invention has a configuration in which the
second partition member has a porous plate having a number of
through holes. A twenty-first invention has a configuration in
which the third partition member has a porous plate having a number
of through holes. According to the configurations of the twentieth
and twenty-first inventions, the excellent sound absorbing
performance in which the frequency band having the high sound
absorption coefficient is enlarged can be obtained. A twenty-second
invention may have a configuration in which the second partition
member has foil which is provided vibratably or rubbably. A
twenty-third invention may have a configuration in which the third
partition member has foil which is provided vibratably or rubbably.
In this case, the foil of the twenty-second invention may have a
number of through holes (twenty-fourth invention), and the foil of
the twenty-third invention may have a number of through holes
(twenty-fifth invention). The foil of the twenty-second invention
may have a convex-convex portion (twenty-sixth invention), and the
foil of the twenty-third invention may have a convex-convex portion
(twenty-seventh invention).
[0014] In the sixteenth invention, a twenty-eighth invention has a
configuration in which a sound absorbing material is provided in at
least one of the at-least-two second partitioned spaces. In the
nineteenth invention, a twenty-ninth invention has a configuration
in which a sound absorbing material is provided in at least one of
the at-least-two third partitioned spaces. According to the
configurations of the twenty-eighth and twenty-ninth inventions,
the excellent sound absorbing performance in which the frequency
band having the high sound absorption coefficient is enlarged can
be obtained.
[0015] In the sixteenth invention, a thirtieth invention has a
configuration in which only one of the at-least-two second
partitioned spaces is communicated with the outside space. In the
nineteenth invention, a thirty-first invention has a configuration
in which only one of the at-least-two third partitioned spaces is
communicated with the outside space. According to the thirtieth and
thirty-first inventions, the configuration is simplified.
[0016] Further, the present invention is a method of producing a
sound absorbing structure body comprising a concave-convex plate
which includes a concave-convex portion and an opening; a closure
plate which is bonded to the concave-convex plate so as to form a
hollow portion by closing one of the concave-convex portion, the
hollow portion being communicated with an outside space through the
opening; and a first partition member which partitions the hollow
portion into at least two first partitioned spaces, the sound
absorbing structure body producing method wherein a support hole is
formed in the first partition member, the support hole is inserted
into a convex portion of the concave-convex plate, the support hole
is supported and fixed by the convex portion in the midway of the
insertion, and thereby the first partition member is provided in
the hollow portion. The present invention is a method of producing
a sound absorbing structure body comprising a concave-convex plate
which includes a concave-convex portion and an opening; a closure
plate which is bonded to the concave-convex plate so as to form a
hollow portion by closing one of the concave-convex portion, the
hollow portion being communicated with an outside space through the
opening; and a first partition member which partitions the hollow
portion into at least two first partitioned spaces, the sound
absorbing structure body producing method wherein a fitting convex
portion is formed in the first partition member, the fitting convex
portion is fitted into a convex portion of the concave-convex
plate, the fitting convex portion is supported and fixed by the
convex portion in the midway of the fitting, and thereby the first
partition member is provided in the hollow portion.
[0017] The present invention is a method of producing a sound
absorbing structure body comprising an interior member which
includes an opening; an exterior member which is arranged opposite
to the interior member while separated from the interior member; a
coupling member which couples the interior member and the exterior
member to form a hollow portion communicated with an outside space
through the opening; and a second partition member which partitions
the hollow portion into at least two second partitioned spaces, the
interior member being a concave-convex plate having a
concave-convex portion, which is integrated with the coupling
member and formed by the coupling member, the exterior member being
a closure plate which is bonded to close one of the concave-convex
portion, the sound absorbing structure body producing method
wherein a support hole is formed in the second partition member,
the support hole is inserted into a convex portion of the
concave-convex plate, the support hole is supported and fixed by
the convex portion in the midway of the insertion, and thereby the
second partition member is provided in the hollow portion. The
present invention is a method of producing a sound absorbing
structure body comprising an interior member which includes an
opening; an exterior member which is arranged opposite to the
interior member while separated from the interior member; a
coupling member which couples the interior member and the exterior
member to form a hollow portion communicated with an outside space
through the opening; and a second partition member which partitions
the hollow portion into at least two second partitioned spaces, the
interior member being a concave-convex plate having a
concave-convex portion, which is integrated with the coupling
member and formed by the coupling member, the exterior member being
a closure plate which is bonded to close one of the concave-convex
portion, the sound absorbing structure body producing method
wherein a fitting convex portion is formed in the second partition
member, the fitting convex portion is fitted into a convex portion
of the concave-convex plate, the fitting convex portion is
supported and fixed by the convex portion in the midway of the
fitting, and thereby the second partition member is provided in the
hollow portion. Further, the present invention has a configuration
in which a number of through holes are formed in the second
partition member. Accordingly, the sound absorbing structure body
having the partitioned space can easily be produced with high
accuracy.
Effect of the Invention
[0018] The present invention has an advantage that the frequency
band having a high sound absorption coefficient can be enlarged to
obtain an excellent sound absorbing performance, since the present
invention includes the porous plate which partitions the hollow
portion into at least two partitioned spaces.
BEST MODE FOR CARRYING OUT THE INVENTION
[0019] (First Embodiment)
[0020] A first embodiment of the present invention will be
described below with reference to FIGS. 1 to 4.
[0021] A sound absorbing structure body according to the first
embodiment is preferably used for a sound insulating cover, a
structural member, and a panel of a moving apparatus such as an
automobile, a railroad car, a construction vehicle, a ship, and an
automatic transportation apparatus including a drive mechanism such
as an engine therein and an installation machine including a drive
mechanism such as a motor and a gear therein, or a floor, a wall,
and a ceiling of a building.
[0022] As shown in FIG. 1, the sound absorbing structure body has a
flat-plate-shaped closure plate 1 and a concave-convex plate 2. The
flat-plate-shaped closure plate 1 faces an outside where, for
example, noises become problematic, and the concave-convex plate 2
faces a sound source side from which the noise is generated due to
the drive mechanism such as the engine. The closure plate 1 and the
concave-convex plate 2 are made of metal such as iron and aluminum
or of a resin material. It is desirable that the closure plate 1
and the concave-convex plate 2 be made of the same material such
that a segregation process is eliminated in recycling.
[0023] The concave-convex plate 2 has a flat-plate-shaped concave
portion 4 and a plurality of convex portions 3. The convex portion
3 is protruded toward a direction of the closure plate 1 from the
concave portion 4, and the convex portion 3 is bonded to the
closure plate 1. A number of openings 5 are formed in the concave
portion 4. The convex portions 3 are dispersed at predetermined
intervals. The convex portion 3 may be continuously provided from
one end to the other end. The opening 5 may further be formed in
the convex portion 3.
[0024] The convex portion 3 is formed in a conical shape while
including a flat top portion 3a and a side surface portion 3b. The
side surface portion 3b is inclined while a diameter of the side
surface portion 3b is enlarged from a circumference of the top
portion 3a. The closure plate 1 is bonded to the top portion 3a of
the convex portion 3 so as to close the concave portion 4.
Therefore, a hollow portion 6 is formed between the closure plate 1
and the concave-convex plate 2. The hollow portion 6 is surrounded
by the concave portion 4, the closure plate 1, and the convex
portion 3, and the hollow portion 6 is communicated with an outside
space through the opening 5.
[0025] A first porous plate 11 and a second porous plate 12 (first
partition member) are provided in the hollow portion 6. The first
and second porous plates 11 and 12 are arranged in parallel with
the concave portion 4. The hollow portion 6 is partitioned into
three-layer partitioned spaces 8, 9, and 10 sequentially from the
sound source side by the first and second porous plates 11 and 12.
The porous plates 11 and 12 include a number of through holes 11a
and 12a and support holes 11b and 12b respectively. The support
holes 11b and 12b are arranged so as to have a positional
relationship aligned with an arrangement position of the convex
portion 3, and hole diameters of the support holes 11b and 12b are
set such that the support holes 11b and 12b are supported by the
side surface portion 3b of the convex portion 3. That is, the first
porous plate 11 located close to the sound source side differs from
the second porous plate 12 located far away from the sound source
side in terms of the hole diameter of the support holes 11b and
12b. In other words, the hole diameter of the support hole 11b in
the first porous plate 11 is enlarged compared with the hole
diameter of the support hole 12b in the second porous plate 12. In
the first and second porous plates 11 and 12, the side surface
portion 3b of the convex portion 3 abut onto and support the
support holes 11b and 12b having different diameters from each
other at different portions on the side surface portion 3b in the
midway in which the support holes 11b and 12b are inserted into the
convex portion 3. This causes layer thicknesses d1, d2, and d3 of
the partitioned spaces 8, 9, and 10 to be set respectively.
[0026] A multi-degree-of-freedom vibration system is formed in the
state, in which the air in each of the partitioned spaces 8, 9, and
10 acts as a spring and the air in each of the through holes 11a
and 12a of the porous plates 11 and 12 acts as a mass. When the
sound having a resonance frequency of a resonance system of the
multi-degree-of-freedom vibration system is incident from the
opening 5, the air in the through holes 11a and 12a in the porous
plates 11 and 12 is intensively vibrated to exhibit large sound
absorbing power by friction loss.
[0027] In at least one member of the through holes 11a and 12a in
the first and second porous plates 11 and 12, parameters including
a numerical aperture .beta., a plate thickness t, and a hole
diameter b are preferably a combination in which the parameter
independently exerts a sound absorption coefficient not lower than
0.3.
[0028] It is preferable that the parameters including the layer
thickness d, the numerical aperture .beta., the plate thickness t,
and the hole diameter b are set so as to generate a viscous action
to the air passing through at least any one of the opening 5 in the
concave-convex plate 2 and the through holes 11a and 12a in the
first and second porous plates 11 and 12. This is because, when the
sound absorbing structure body is formed based on the parameters,
the viscous action is generated in the air to create vibration and
damping, enabling the sound absorbing characteristics in which a
frequency band width whose sound absorption coefficient is not
lower than 0.3 becomes not lower than 10% for a resonance frequency
f.
[0029] That is, in order that the parameters of the sound absorbing
structure body have the above sound absorbing characteristics,
design conditions are preferably set such that at least one of the
concave-convex plate 2 and the porous plates 11 and 12 have the
numerical aperture .beta. not more than 3%, each plate thickness t
is not lower than 0.3 mm, and the opening 5 and the through holes
11a and 12a have the hole diameters b not more than 0.8 mm.
[0030] Although the hole diameters of the opening 5 and the through
holes 11a and 12a are not particularly limited, any one of the
members has the hole diameter not more than 5 mm, preferably not
more than 3 mm, and more preferably not more than 1 mm. The sound
absorbing structure body may be formed only by focusing on the hole
diameters of the opening 5 and the through holes 11a and 12a. That
is, the sound absorbing structure body may be configured to have
the first and second porous plates 11 and 12 having a number of
through holes 11a and 12a whose diameters are not more than 1 mm.
In the case where the hole diameters of the through holes 11a and
12a are set to not more than 1 mm, the viscous action can securely
be generated in the air flowing through the through holes 11a and
12a.
[0031] It is preferable that a lower limit of the diameters of the
opening 5 and the through holes 11a and 12a are 0.2 mm. This is
attributed to the fact, although a peak of the sound absorption
coefficient theoretically becomes 1.0 when the diameter of the
through holes 11a and 12a comes to close to zero, the sound
absorption coefficient does not actually reach 1.0, and the
viscosity of the air in the through holes 11a and 12a is
excessively increased when the diameter becomes as extremely small
as a diameter not more than 0.2 mm, so that resistance of the
through holes 11a and 12a against the air flow is increased to
adversely decrease the sound absorption coefficient. Further, it is
attributed to the fact that when the diameter becomes as extremely
small as a diameter not more than 0.2 mm, production becomes
largely difficult, and the through holes 11a and 12a are easily
closed by dirt and dust depending on use environment.
[0032] The opening 5 and the through holes 11a and 12a may be
formed in an elliptical shape, a rectangular shape, a polygon
shape, or a slit shape. Various shapes may be mixed between and
inside the opening 5 and the through holes 11a and 12a. Each of the
opening 5 and the through holes 11a and 12a may be formed in the
same dimension and diameter, or various dimensions and diameters
may be mixed between and inside the opening 5 and the through holes
11a and 12a. In case where the various dimensions and diameters are
mixed, the frequency band width in which a sufficient sound
absorbing performance is exerted can be enlarged.
[0033] The sound absorbing structure body of the first embodiment
has the configuration in which the partitioned spaces 8, 9, and 10
of layers are arranged in parallel, the present invention is not
limited to the first embodiment. That is, the partitioned spaces 8,
9, and 10 of the sound absorbing structure body may be divided or
partitioned into arbitrary shapes and volumes in the hollow portion
6 by the partition members which partition the hollow portion 6.
For example, the porous plates 11 and 12 may be provided at equal
intervals such that the layer thicknesses of the partitioned spaces
8, 9, and 10 become equalized, or the porous plates 11 and 12 may
unevenly be provided such that the layer thicknesses become
unequal. In this case, the sound absorbing performance can easily
be adjusted by changing the partition member.
[0034] In the first embodiment, the porous plates 11 and 12 are
provided in the hollow portion 6. In addition, as shown in FIG. 11,
a porous plate 14 (third partition member) and a porous plate 15
(closure member) may be provided in an opening portion 7,
surrounded by the top portion 3a and the side surface portion 3b of
the convex portion 3, which is located adjacent to the hollow
portion 6. In this case, in order to largely take an air layer, the
porous plate 14 and/or the porous plate 15 may have the
configuration in which the porous plate 14 and/or the porous plate
15 are/is raised toward the opposite direction to the convex
portion 3. On the contrary, in case where a sound having a high
frequency is absorbed, since a thin air layer may be formed, the
porous plate 14 and/or the porous plate 15 may have a structure in
which the porous plate 14 and/or the porous plate 15 is recessed
toward the direction to the convex portion 3. Only the porous plate
15 may be provided while the porous plate 14 is not provided. The
porous plates 14 and 15 may be formed by metal foil or a thin film.
In this case, the metal foil and the thin film may have the through
hole, or the metal foil and thin film may have no through hole.
[0035] In the above configuration, a sound absorbing structure body
producing method will be described.
[0036] First it is actually measured or estimated what kind of
frequency characteristics are possessed by noises which are of a
sound absorbing target. In order to obtain the sound absorbing
characteristics in which the sound absorption coefficient of the
frequency band width including a plurality of peak components
becomes not lower than 0.3, the parameters are determined in
consideration to the air viscosity based on the design conditions,
in which the layer thicknesses d1, d2, and d3 are from 1 mm to 50
mm, the numerical apertures .beta. of the concave-convex plate 2
and the first and second porous plates 11 and 12 are not more than
15%, the plate thicknesses t are not lower than 0.3 mm, and the
hole diameters b of the opening 5 and the through holes 11a and 12a
are not more than 0.8 mm.
[0037] Then, as shown in FIG. 2, the sound absorbing structure body
is produced based on the parameters. Specifically, the metal plate
made of iron or aluminum having a predetermined thickness is
prepared and set in a press working machine. The metal plate is
press-worked to bore the opening 5 while the convex portion 3 is
simultaneously formed, which produces the concave-convex plate 2.
The metal plates in which the small-diameter through holes 11a and
12a are previously formed are prepared, and the support holes 11b
and 12b are respectively formed by the press working similarly to
the concave-convex plate 2, which respectively produces the first
porous plate 11 and the second porous plate 12. The through holes
11a and 12a may simultaneously be formed along with the support
holes 11b and 12b by the press working.
[0038] After the concave-convex plate 2 is set on a base, the
concave-convex plate 2 is capped with the first porous plate 11
from the upper side of the concave-convex plate 2, and the convex
portion 3 is inserted into the support hole 11b. When the side
surface portion 3b of the convex portion 3 abut on and support the
support hole 11b during the insertion of the convex portion 3 into
the support hole 11b, the first porous plate 11 is pressed with a
predetermined pressure from the upper side toward the direction of
the concave-convex plate 2, which achieves press-contact of the
support hole 11b to the convex portion 3 to establish fixation. In
order to ensure the fixation, the convex portion 3 and the support
hole 11b may be bonded and fixed at an abutting portion by a
bonding agent or welding, or the convex portion 3 and the support
hole 11b may be coupled with screws. The hollow portion 6 may
completely be sealed by the closure plate 1 and the concave-convex
plate 2, or the hollow portion 6 may not completely be sealed in
case where the closure plate 1 and the top portion 3a are bonded at
only one point. That is, the adjacent hollow portions 6 may be
communicated with each other through a gap generated between the
closure plate 1 and the top portion 3a.
[0039] Then, the first porous plate 11 is capped with the second
porous plate 12 from the upper side of the first porous plate 11.
As with the first porous plate 11, the support hole 12b of the
second porous plate 12 is supported and fixed by the convex portion
3 during the insertion into the support hole 12b. Then, the closure
plate 1 is placed on the top portion 3a of the convex portion 3
protruded from the support hole 12b of the second porous plate 12,
and fixed to the top portion 3a with the bonding agent or the like.
Therefore, in the first and second porous plates 11 and 12, while
the support holes 11b and 12b having different diameters from each
other are fixed to the side surface portion 3b of the convex
portion 3 at different portion of the side surface portion 3b, the
closure plate 1 is fixed to the top portion 3a of the convex
portion 3, which enables the sound absorbing structure body
including the partitioned spaces 8, 9, and 10 having the layer
thicknesses d1, d2, and d3 to be easily produced with high
accuracy.
[0040] In case where the porous plates 14 and 15 are provided in
the opening portion 7, for example, the porous plates 14 and 15
having different diameters from each other are produced, and the
sound absorbing structure body is produced by arranging the porous
plates 14 and 15 from the top portion 3a side of the convex portion
3 toward the opening in the order of the porous plate having the
smaller diameter.
[0041] Then, an operation of the sound absorbing structure body
will be described.
[0042] When the sound source generates the noise, the noise runs on
and reaches the sound absorbing structure body arranged opposing to
the sound source. In this case, the sound absorbing structure body
is formed with the numerical aperture, the plate thickness of the
interior plate, the hole diameter, and the air layer thickness
which are all configured to satisfy a required performance. The
sound absorbing structure body is configured to include the
three-layer partitioned spaces 8, 9, and 10 in which the sound
absorbing characteristics exhibit a high sound absorption
coefficient in the neighboring bands of a plurality of the
resonance frequencies. Accordingly, when the noise reaches the
sound absorbing structure body, the noise components of the
neighboring bands of a plurality of the resonance frequencies are
absorbed by the high sound absorption coefficient, so that the main
and wide-frequency-band noises generated by the sound source such
as the engine can be absorbed. Therefore, the sound absorbing
structure body can absorb the main and wide-frequency-band
noises.
[0043] Thus, the sound absorbing structure body of the first
embodiment is configured to include the concave-convex plate 2, the
closure plate 1, and the first and second porous plates 11 and 12.
The concave-convex plate 2 includes the convex portion 3, the
concave portion 4 (concave-convex portion), and the opening 5. The
closure plate 1 is bonded to the concave-convex plate 2 so as to
form the hollow portion 6, communicated with the outside space
through the opening 5, by closing one of the convex portion 3 and
the concave portion 4. The first and second porous plates 11 and 12
have a number of the through holes 11a and 12a respectively, and
the first and second porous plates 11 and 12 partition the hollow
portion 6 into at least two partitioned spaces.
[0044] Although the present invention is described based on the
preferred embodiment, the change could be made without departing
from the scope of the present invention.
[0045] For example, in the first embodiment, the closure plate 1,
the concave portion 4, and the like are formed in a flat plate
shape. However, the present invention is not limited to this, but
the closure plate 1, the concave portion 4, and the like may
locally have a concave and convex plane or a curved plane or
partially have a step. In the first embodiment, a case where a
plurality of the convex portions 3 are dispersed, while the two
porous plates 11 and 12 are provided in the hollow portion 6 formed
by the concave portion 4 and the closure plate 1 was explained.
However the present invention is not limited to the first
embodiment. That is, as shown in FIG. 3, the sound absorbing
structure body may be configured to provide at least three porous
plates 21 in the hollow portion 6 formed by the concave portion 4
and the closure plate 1 while having the concave-convex plate 2 in
which the convex portion 3 is formed so as to surround the
circumference of one concave portion 4. In this case, since a
number of the partitioned spaces 8, 9, . . . , and 10 are formed by
the porous plates 21, the number of peak frequencies can further be
increased to realize a broader band of the sound absorbing
performance. It is obvious that one porous plate 21 may be provided
in the hollow portion. The through hole 21a of each porous plate 21
may be formed in various shapes such as an elliptical shape, a
rectangular shape, a polygon shape, and a slit shape. The same
shape or the same diameter may exist between and inside the porous
plates 21 or the various shapes or the various diameters may be
mixed between and inside the porous plates 21.
[0046] As shown in FIG. 4, the sound absorbing structure body may
be formed in the structure in which the configurations of FIG. 3
are arranged in line or arranged in a matrix shape. In this case,
the sound absorbing power can be improved. In the opening 5 of the
concave-convex plate 2 and the through hole 21a of the porous plate
21, the same shape or the same diameter may exist between and
inside the hollow portion 6 or the various shapes or the various
diameters may be mixed between and inside the hollow portion 6
arranged in parallel. Therefore, the sound absorbing performance
having a wider peak frequency can be obtained. Although the
numerical values such as the numerical aperture .beta., the layer
thickness d, and the plate thickness t are specifically described,
the present invention is not limited to them. The numerical values
are determined by an environment in which the sound absorbing
structure body according to the first embodiment is placed, a
required strength and morphology, and the like.
[0047] (Second Embodiment)
[0048] A second embodiment of the present invention will be
described below with reference to FIGS. 5 and 6. In the second
embodiment, the same component as the first embodiment is
designated by the same numeral, and the description will be
omitted.
[0049] As shown in FIG. 5, a sound absorbing structure body
according to the second embodiment has the closure plate 1 and the
concave-convex plate 2. The concave-convex plate 2 has the
flat-plate-shaped concave portion 4 and a plurality of the convex
portions 3. A number of the openings 5 are formed in the concave
portion 4. The hollow portion 6 is formed between the closure plate
1 and the concave-convex plate 2. A first porous plate 31 and a
second porous plate 32 are provided in the hollow portion 6. The
first porous plate 31 and the second porous plate 32 include a
number of through holes 31a and 32a and fitting convex portions 31b
and 32b.
[0050] The fitting convex portions 31b and 32b are arranged so as
to have a positional relationship aligned with an arrangement
position of the convex portion 3. The fitting convex portions 31b
and 32b are set in conical shapes having different depths from each
other, and the fitting convex portions 31b and 32b have outer
shapes supported by the side surface portion 3b and the top
portions 3a of the convex portion 3. That is, the first porous
plate 31 located close to the sound source side differs from the
second porous plate 32 located far away from the sound source side
in the depth. In other words, the depth of the fitting convex
portions 31b of the first porous plate 31 is enlarged compared with
the depth of the fitting convex portions 32b of the second porous
plate 32. In the first and second porous plates 31 and 32, the
fitting convex portions 31b and 32b having different depths from
each other are fitted into the convex portion 3, and the side
surface portion 3b and the top portion 3a of the convex portion 3
abut on and support the fitting convex portions 31b and 32b in the
midway of the fitting, which sets the layer thicknesses d1, d2, and
d3 of the partitioned spaces 8, 9, and 10 respectively. Similarly
to the first embodiment, the porous plates 31 and 32 may be
provided at equal intervals such that the layer thicknesses d1, d2,
and d3 become equalized, or the porous plates 31 and 32 may
unevenly be provided such that the layer thicknesses become
unequal. Other configurations are similar to those of the first
embodiment, and the above-described configurations of the first
embodiment or the configurations of the modification of the first
embodiment may be applied as appropriate.
[0051] In the above configuration, a sound absorbing structure body
producing method will be described.
[0052] As shown in FIG. 6, the sound absorbing structure body is
produced by the parameters previously determined by the method of
the first embodiment. Specifically, the metal plate made of iron or
aluminum is press-worked to bore the opening 5 while the convex
portion 3 is simultaneously formed, which produces the
concave-convex plate 2. The metal plates in which the
small-diameter through holes 31a and 32a are previously formed are
prepared, and the fitting convex portions 31b and 32b are
respectively formed by the press working similarly to the
concave-convex plate 2, which respectively produces the first
porous plate 31 and the second porous plate 32. The through holes
31a and 32a may simultaneously be formed along with the fitting
convex portions 31b and 32b by the press working.
[0053] Then, the concave-convex plate 2 is capped with the first
porous plate 31 from the upper side of the concave-convex plate 2,
and the convex portion 3 is fitted into the fitting convex portion
31b. When the top portion 3a and side surface portion 3b of the
convex portion 3 abut on and support the fitting convex portion
31b, the first porous plate 31 is capped with the second porous
plate 32 from the upper side of the first porous plate 31. The
fitting convex portion 31b of the first porous plate 31 is fitted
into the fitting convex portion 32b of the second porous plate 32,
which allows the first porous plate 31 and the second porous plate
32 to be positioned and fixed. The fixation may be performed with
the bonding agent. Then, the closure plate 1 is placed on the
fitting convex portion 32b of the second porous plate 32, and the
closure plate 1 is bonded to the fitting convex portion 32b with
the bonding agent or the like. Therefore, in the first and second
porous plates 31 and 32, while the fitting convex portion 31b and
32b having different dimensions (depths) from each other are fixed
at the convex portion 3, the closure plate 1 is fixed to the top
portion of the fitting convex portion 32b, which enables the sound
absorbing structure body including the partitioned spaces 8, 9, and
10 having the layer thicknesses d1, d2, and d3 to be easily
produced with high accuracy. Other producing methods are similar to
those of the first embodiment.
[0054] According to the sound absorbing structure body which is
produced and configured in the above-described manner, the noise
components of the neighboring bands of a plurality of the resonance
frequencies are absorbed by the high sound absorption coefficient,
so that the main and wide-frequency-band noises generated by the
sound source such as the engine can be absorbed.
[0055] (Third Embodiment)
[0056] A third embodiment of the present invention will be
described below with reference to FIG. 7. In the third embodiment,
the same component as the first embodiment is designated by the
same numeral, and the description will be omitted.
[0057] As shown in FIG. 7, in a sound absorbing structure body
according to the third embodiment, a plurality of porous plates 41
are provided in the hollow portion 6 which is formed by the
concave-convex plate 2 and the opening 5 bonded to the
concave-convex plate 2. In the concave-convex plate 2, a number of
openings 5 are provided in the convex portion 3 and the concave
portion 4. Similarly to the first embodiment, the porous plate 41
has a number of through holes 41a, and the porous plate 41 has the
support holes 41b set at the hole diameters according to the layers
respectively. A plurality of the porous plates 41 may be provided
at equal intervals, or the porous plates 41 may be provided at
uneven intervals. A thin-film sound absorbing body 44 is provided
in the hollow portion 6. The thin-film sound absorbing body 44 may
be provided among a plurality of the porous plates 41. The
thin-film sound absorbing body 44 may be provided between the
porous plate 41 and the concave-convex plate 2 or between the
porous plate 41 and the closure plate 1, and it is desirable that
the thin-film sound absorbing body 44 be provided in the optimum
arrangement state according to the sound source which is of the
sound absorbing target.
[0058] The thin-film sound absorbing body 44 includes two thin
films 42 and 43. In the thin films 42 and 43, surfaces are formed
in a plane. The surfaces of the thin films 42 and 43 are slightly
separated from each other, and the surfaces are adjacent to each
other while being able to come into contact with each other during
the vibration. Although a metal thin film formed by aluminum foil,
a thin film made of a resin such as vinyl chloride, and the like
can be used as the thin films 42 and 43, the thin films 42 and 43
are not limited to the above thin films. Other configurations are
similar to those of the first embodiment, and the above-described
configurations of the first embodiment or the configurations of the
modification of the first embodiment may be applied as
appropriate.
[0059] Thus, in the sound absorbing structure body of the third
embodiment, at least one thin-film sound absorbing body 44 (foil)
is provided in at least one of partitioned spaces into which the
hollow portion 6 is partitioned while the thin-film sound absorbing
body 44 can vibrate or rub against each other. According to the
configuration of the third embodiment, in the sound absorbing
structure body, in addition to an operation in which the same sound
absorbing performance as the first embodiment is exerted, the two
thin films 42 and 43 vibrate by incidence of an acoustic wave, and
the thin films 42 and 43 come into contact with each other to rub
against each other with the vibration, which allows acoustic energy
to be lost. Therefore, compared with the configuration in which the
energy is dissipated by the resonance phenomenon, an excellent
sound absorbing performance can be exerted in a broad band. Since
the thin-film sound absorbing body 44 made of the metal such as
aluminum foil or the resin such as vinyl chloride can be used as
the sound absorbing structure body, the thin-film sound absorbing
body 44 is easily recycled compared with a difficult-to-recycle
material such as glass-wool which is conventionally to be disposed
of as shredder dust and the like.
[0060] The thin films 42 and 43 may have a number of minute convex
portions, and the thin films may be laminated such that the thin
films come into contact with each other by the convex portions. In
this case, when the acoustic wave is incident, the thin films 42
and 43 vibrate and the overlapped portions come into contact with
each other to rub against each other, so that the acoustic wave
energy can be dissipated to realize the sound absorption.
[0061] In the thin films 42 and 43 of the thin-film sound absorbing
body 44, the fine through holes are formed in the thickness
direction, and the through holes in the thin films 42 and 43 may be
overlapped each other or not overlapped each other when viewed in
the laminated direction. In the case where the through holes are
overlapped, not only the thin films 42 and 43 vibrate and rub
against each other to achieve an excellent sound deadening effect
in a broad band, but also the more excellent sound deadening effect
can be exerted since the acoustic wave is further damped when the
acoustic wave passes through the through hole.
[0062] In case where a through hole of one of the thin films 42 and
43 is formed at the position where the through hole is not
overlapped with the through hole of the other thin film, the
acoustic wave passes through the through hole of the thin film 43
from the incident side, runs between the two thin films 42 and 43,
and passes through the through hole of the thin film 42.
Accordingly, since the acoustic wave propagates along inner
surfaces of the two thin films 42 and 43, the sound deadening
effect is further exerted by both a damping action in the passage
of the acoustic wave through the through hole and a viscous damping
action in the propagation of the acoustic wave on the surface of
the thin films 42 and 43. In the thin-film sound absorbing body 44,
a further excellent damping effect is obtained by forming a fine
through hole, which remarkably improves the sound deadening effect.
The through hole may not be formed in the thin-film sound absorbing
body 44.
[0063] Instead of the convex portion, the thin-film sound absorbing
body 44 may be folded so as to have regions overlapped with each
other while being in contact with each other. In this case, when
the overlapped regions come into contact with each other to rub
against each other, the acoustic wave energy can be dissipated,
which allows the high sound absorption coefficient to be realized
in the broad band. Even if two thin films 42 and 43 are decreased
to one, the sound absorbing structure can be achieved in the
overlapped portion, so that cost can be reduced.
[0064] In the third embodiment, the porous plate 41 and the
thin-film sound absorbing body 44 are provided in the sound
absorbing structure body. However, since the thin-film sound
absorbing body 44 has the sound absorbing effect in itself, only
the thin-film sound absorbing body 44 may be provided in the sound
absorbing structure body. Similarly to the first embodiment, as
shown in FIG. 12, a thin-film sound absorbing body 45 may be
provided in the opening portion 7 surrounded by the top portion 3a
and side surface portion 3b of the convex portion 3. In this case,
the thin-film sound absorbing body 45 may be a porous plate similar
to the porous plate 41, or both the thin-film sound absorbing body
45 and the porous plate may be provided.
[0065] (Fourth Embodiment)
[0066] A fourth embodiment of the present invention will be
described below with reference to FIG. 8. In the fourth embodiment,
the same component as the first and third embodiments is designated
by the same numeral, and the description will be omitted.
[0067] As shown in FIG. 8, in a sound absorbing structure body
according to the fourth embodiment, a plurality of the porous
plates 41 are provided in the hollow portion 6 which is formed by
the concave-convex plate 2 and the opening 5 bonded to the
concave-convex plate 2. In the concave-convex plate 2, a number of
the openings 5 are provided in the convex portion 3 and the concave
portion 4. Similarly to the third embodiment, a plurality of the
porous plates 41 may be provided at equal intervals, or the porous
plates 41 may be provided at uneven intervals. A sound absorbing
material 51 is provided in the hollow portion 6. The sound
absorbing material 51 is provided in an arbitrary region
(partitioned space) of the hollow portion 6. For example, the sound
absorbing material 51 is provided in the whole portion or a part of
the portion between the porous plate 41 and the closure plate 1,
between the porous plates 41 and 41, or between the porous plate 41
and the concave-convex plate 2. The region where the sound
absorbing material 51 is provided may be located at the same
position or at different position in each hollow portion 6.
[0068] The sound absorbing material 51 is made of a porous
material. The porous material may be formed by compressing metal
fiber or strip metal such as aluminum, stainless, glass-wool, and
PET fiber. The porous material may be made of non-woven fabric, or
made of metal or resin foaming material. In the porous material,
when the closure plate 1 and the concave-convex plate 2 are made of
metal, it is desirable that the porous material be made of the same
metal such that a good recycling property is obtained. Other
configurations are similar to those of the first and third
embodiments, and the above-described configurations of the first
and third embodiments or the configurations of the modification of
the first and third embodiments may be applied as appropriate.
[0069] According to the configuration of the fourth embodiment, in
the sound absorbing structure body, the sound absorbing material 51
can absorb the noises of the band wider than the frequency band
which can sufficiently be absorbed by the Helmholtz Resonance
Principle, so that the sound absorbing structure body can further
improve the sound insulating performance.
[0070] In the fourth embodiment, only the sound absorbing material
51 is provided in the hollow portion 6. However, the present
invention is not limited to the fourth embodiment, but the sound
absorbing material 51 may be provided along with the thin-film
sound absorbing body 44 of the third embodiment. The sound
absorbing structure body may have the configuration in which the
sound absorbing material 51 is provided around the concave-convex
plate 2. Similarly to the first embodiment, as shown in FIG. 13, a
sound absorbing material 52 may be provided in the opening portion
7 surrounded by the top portion 3a and side surface portion 3b of
the convex portion 3.
[0071] (Fifth Embodiment)
[0072] A fifth embodiment of the present invention will be
described below with reference to FIG. 14. In the fifth embodiment,
the same component as the first to fourth embodiments is designated
by the same numeral, and the description will be omitted.
[0073] As shown in FIG. 14, a sound absorbing structure body
according to the fifth embodiment includes a flat-plate-shaped
interior plate 2a interior member), the closure plate 1 (exterior
member), and a coupling member 13. The interior plate 2a has a
number of the openings 5. The closure plate 1 is arranged opposite
to the interior plate 2a while separated from the interior plate
2a. The coupling member 13 couples the interior plate 2a and the
closure plate 1 to form the hollow portion 6. The closure plate 1
and the interior plate 2a are plate members made of metal such as
iron and aluminum, the resin material, or the foil. The coupling
member 13 includes a flat top portion 13a and a side surface
portion 13b provided in the circumference of the top portion 13a,
and the coupling member 13 is formed in a columnar shape. That is,
the coupling member 13 has the same configuration as the convex
portion 3 of the first embodiment. The interior plate 2a and the
closure plate 1 are coupled to each other such that the top portion
13a is bonded to the closure plate 1, which forms the hollow
portion 6 between the coupling members 13. The coupling member 13
may be formed in the shape with no top portion 13a, i.e., in a
cylindrical shape having only the side surface portion 13b.
[0074] The hollow portion 6 is communicated with the outside space
through the opening 5. A first porous plate 61 and a second porous
plate 62 (second partition member) are provided in the hollow
portion 6. The first and second porous plates 61 and 62 include a
number of through holes 61a and 62a. The first and second porous
plates 61 and 62 are arranged in parallel with the interior plate
2a, and the first and second porous plates 61 and 62 partition the
hollow portion 6 into the three-layer partitioned spaces 8, 9, and
10 in the order from the sound source side. The porous plates 61
and 62 may be provided at equal intervals such that the layer
thicknesses of the partitioned spaces 8, 9, and 10 become
equalized, or the porous plates 61 and 62 may unevenly be provided
such that the layer thicknesses become unequal. The action of the
sound absorbing structure body of the fifth embodiment is similar
to that of the first embodiment, so that the description will be
omitted.
[0075] Thus, the sound absorbing structure body of the fifth
embodiment is configured to include the interior plate 2a (interior
member), the closure plate 1 (exterior member), the coupling member
13, and the first and second porous plates 61 and 62 (second
partition member). The interior plate 2a includes the openings 5.
The closure plate 1 is arranged opposite to the interior plate 2a
while separated from the interior plate 2a. The coupling member 13
couples the interior plate 2a and the closure plate 1 to form the
hollow portion 6 communicated with the outside through the opening
5. The first and second porous plates 61 and 62 partitions the
hollow portion 6 into at least two partitioned spaces. According to
the configuration of the fifth embodiment, similarly to the first
embodiment, the effect that an excellent sound absorbing
performance in which the frequency band having the high sound
absorption coefficient is enlarged can be obtained. The coupling
member 13 and the interior plate 2a can be formed with different
members by individually forming the coupling member 13 and the
interior plate 2a.
[0076] Although the coupling member 13 of the fifth embodiment is
formed in a columnar shape, the coupling member 13 may be formed in
other shapes. The coupling member 13 may be formed in any shape as
long as the closure plate 1 and the interior plate 2a are coupled
to form the hollow portion 6. For example, the coupling member 13
may be formed in a conical shape or a cylindrical shape whose cross
section has polygon. The coupling member 13 shown in FIG. 14 may be
formed in a plate shape. In the case where the coupling member 13
is formed in the plate shape, as shown in FIG. 15, the first and
second porous plates 61 and 62 may be provided between the coupling
members 13 and 13. In this case, a higher sound absorption
coefficient can be obtained. At least two porous plates may be
provided. In this case, since a number of the partitioned spaces 8,
9, . . . , and 10 are formed by the porous plate 21, the number of
p peak frequencies can further be increased to realize a broad band
of the sound absorbing performance. Although the porous plates 61
and 62 are provided in the hollow portion 6, the porous plates may
be provided in the opening portion surrounded by the top portion
13a and side surface portion 13b of the coupling member 13 adjacent
to the hollow portion 6. Although the closure plate 1 and the
interior plate 2a are formed in a flat plate shape, the closure
plate 1 and the interior plate 2a may locally have a concave-convex
surface or a curved surface, or the closure plate 1 and the
interior plate 2a may partially have a step.
[0077] The interior plate 2a and the coupling member 13 may be
integrated with each other to form one member. That is, the
interior plate 2a is integrated with the coupling member 13, the
interior plate 2a is a concave-convex plate, formed by the coupling
member 13, having the concave-convex portion, and the closure plate
1 may have the configuration in which the closure plate 1 is bonded
so as to close one of the concave-convex portion. In this case,
since the interior plate 2a and the coupling member 13 can be
produced at once, the sound absorbing structure body can easily be
produced. In this case, an opening having the same width as the
opening portion of the coupling member 13 may be provided in the
interior plate 2a such that the opening portion surrounded by the
top portion 13a and side surface portion 13b of the coupling member
13 is opened. The coupling member 13 may be formed by folding the
closure plate 1, the interior plate 2a, the porous plates 61 and
62, or the like. A plurality of the through holes may be provided
in the coupling member 13. In this case, the resonance generated in
the direction parallel to the closure plate 1 and the interior
plate 2a can be prevented. The damping effect can also be improved
when the acoustic wave passes through the through hole.
[0078] As described in the fourth embodiment, the sound absorbing
members 51 and 52 may be arranged in any one of the partitioned
spaces 8, 9, 10 of the hollow portion 6. The first and second
porous plates 61 and 62 may be formed by the metal foil, the thin
films 42 and 43 described in the third embodiment, or the like. In
this case, the metal foil and the thin film may have a through hole
or may not have the through hole. The above-described
configurations of the first to fourth embodiments or the
configurations of the modification of the first to fourth
embodiments may be applied as appropriate.
[0079] In the configuration of the fifth embodiment, a sound
absorbing structure body producing method will be described. The
producing method described below is the sound absorbing structure
body producing method, in which the interior plate 2a and the
coupling member 13 are integrated and the coupling member 13 forms
concave-convex portion.
[0080] First, similarly to the production method of the first
embodiment, the parameters (layer thicknesses of partitioned spaces
8, 9, and 10, hole diameter of opening 5, and the like) are
determined. Then, as shown in FIG. 16, the sound absorbing
structure body is produced based on the determined parameters.
Specifically, the metal plate made of iron, aluminum or the like
having the predetermined thickness is prepared, and the metal plate
is set in the press working machine. Then, the metal plate is
press-worked to bore the opening 5 while the convex portion 13 (top
portion 13a and side surface portion 13b) is simultaneously formed,
which produces the interior plate 2a. The metal plates in which the
small-diameter through holes 61a and 62a are previously formed are
prepared, and support holes 61b and 62b are respectively formed by
the press working similarly to the interior plate 2a, which
respectively produces the first porous plate 61 and the second
porous plate 62.
[0081] As shown in FIG. 16, the coupling member 13 and the support
holes 61b and 62b are formed so as to be lengthened in one
direction. The coupling member 13 is formed in a shape in which the
diameter is gradually decreased toward the direction in which the
coupling member 13 moves away from the metal plate. The coupling
member 13 can be inserted into the support holes 61b and 62b, and
the support holes 61b and 62b have the diameters with which the
side surface portion 13b of the coupling member 13 is engaged
during the insertion. The through holes 61a and 62a may
simultaneously be formed along with the support holes 61b and 62b
by the press working.
[0082] After the interior plate 2a is set on the base, the interior
plate 2a is capped with the first porous plate 61 from the upper
side of the interior plate 2a, and the coupling member 13 is
inserted into the support hole 61b. When the side surface portion
13b of the coupling member 13 abuts on and support the support hole
61b during the insertion, the first porous plate 61 is pressed with
a predetermined pressure from the upper side in the direction of
the interior plate 2a, which achieves the press-contact of the
support hole 61b to the coupling member 13 to establish the
fixation. In order to ensure the fixation, the coupling member 13
and the support hole 61b may be bonded at the abutting portion by
the bonding agent or the welding, or the coupling member 13 and the
support hole 61b may be coupled with the screws. The hollow portion
6 may completely be sealed by the closure plate 1 and the interior
plate 2a, or the hollow portion 6 may not completely be sealed in
case where the closure plate 1 and the top portion 13a are bonded
at only one point. That is, the adjacent hollow portions 6 may be
communicated with each other through the gap generated between the
closure plate 1 and the top portion 13a.
[0083] Then, the first porous plate 61 is capped with the second
porous plate 62 from the upper side of the first porous plate 61.
As with the first porous plate 61, the support hole 62b of the
second porous plate 62 is supported and fixed by the coupling
member 13 during the insertion. Then, the closure plate 1 is placed
on the top portion 13a of the coupling member 13 protruded from the
support hole 62b of the second porous plate 62, and the closure
plate 1 is bonded and fixed to the top portion 13a with the bonding
agent or the like. Therefore, in the first and second porous plates
61 and 62, while the support holes 61b and 62b having different
diameters from each other are fixed to the side surface portion 13b
of the coupling member 13 at a different portion of the side
surface portion 3b, the closure plate 1 is fixed to the top portion
13a of the coupling member 13, which enables the sound absorbing
structure body including the partitioned spaces 8, 9, and 10 having
the layer thicknesses to be easily produced with high accuracy.
[0084] Thus, the method of producing the sound absorbing structure
body of the fifth embodiment is the method of producing the sound
absorbing structure body including the interior plate 2a (interior
member) which includes the openings 5; the closure plate 1
(exterior member) which is arranged opposite to the interior plate
2a while separated from the interior plate 2a; the coupling member
13 which couples the interior plate 2a and the closure plate 1 to
form the hollow portion communicated with the outside space through
the opening 5; and the porous plates 61 and 62 (second partition
member) which partition the hollow portion 6 into at least two
second partitioned spaces, the interior plate 2a being the
concave-convex plate having the concave-convex portion, which is
integrated with the coupling member 13 and formed by the coupling
member 13, the closure plate 1 being the closure plate which is
bonded to close one of the concave-convex portion, the support
holes 61b and 62b are formed in the porous plates 61 and 62, the
support holes 61b and 62b are inserted into the convex portion of
the concave-convex plate, the support hole is supported and fixed
by the convex portion in the midway of the insertion, and thereby
the porous plates 61 and 62 are provided in the hollow portion
6.
[0085] As shown in FIG. 17, similarly to the producing method in
the second embodiment, fitting convex portions 61c and 62c may be
formed in the first porous plate 61 and the second porous plate 62
as a modification of the producing method of the fifth embodiment.
Specifically, the metal plate made of iron or aluminum is
press-worked to bore the opening 5 while the coupling member 13 is
simultaneously formed, which produces the interior plate 2a. The
coupling member 13 is formed in a flat plate shape from one end of
the metal plate to the other end. The metal plates in which the
small-diameter through holes 61a and 62a are previously formed are
prepared, and the fitting convex portions 61c and 62c are
respectively formed by the press working similarly to the interior
plate 2a, which respectively produces the first porous plate 61 and
the second porous plate 62. The fitting convex portion 61c has the
dimension in which the coupling member 13 can be fitted into the
fitting convex portion 61c, and the coupling member 13 and fitting
convex portion 61c can be fitted into the fitting convex portion
62c. The through holes 61a and 62a may simultaneously be formed
along with the fitting convex portions 61b and 62b by the press
working.
[0086] Then, the interior plate 2a is capped with the first porous
plate 61 from the upper side of the interior plate 2a, and the
coupling member 13 is fitted into the fitting convex portion 61c.
When the top portion 13a and side surface portion 13b of the
coupling member 13 abut on and support the fitting convex portion
61c, the first porous plate 61 is capped with the second porous
plate 62 from the upper side of the first porous plate 61. The
fitting convex portion 61c of the first porous plate 61 is fitted
into the fitting convex portion 62c of the second porous plate 62,
which allows the first porous plate 61 and the second porous plate
62 to be positioned and fixed. The fixation may be performed with
the bonding agent. Then, the closure plate 1 is placed on the
fitting convex portion 62c of the second porous plate 62, and the
closure plate 1 is bonded and fixed to the fitting convex portion
62c with the bonding agent or the like. Therefore, in the first and
second porous plates 61 and 62, while the fitting convex portion
61c and 62c having different dimensions (depths) from each other
are fixed at the coupling member 13, the closure plate 1 is fixed
to the top portion of the fitting convex portion 62c, which enables
the sound absorbing structure body including the partitioned spaces
8, 9, and 10 having the layer thicknesses to be easily produced
with high accuracy. In case where the coupling member 13 is fixed
by the fitting convex portions 61c and 62c, unlike the case where
the coupling member 13 is fixed by the support holes 61b and 62b,
the coupling member 13 can be formed in a flat plate shape, and the
sound absorbing structure body can be formed according to the
circumstances.
[0087] Thus, another method of producing the sound absorbing
structure body of the fifth embodiment is the method of producing
the sound absorbing structure body including the interior plate 2a
(interior member) which includes the openings 5; the closure plate
1 (exterior member) which is arranged opposite to the interior
plate 2a while separated from the interior plate 2a; the coupling
member 13 which couples the interior plate 2a and the closure plate
1 to form the hollow portion communicated with the outside space
through the opening 5; and the porous plates 61 and 62 (second
partition member) which partition the hollow portion 6 into at
least two second partitioned spaces, the interior plate 2a being
the concave-convex plate having the concave-convex portion, which
is integrated with the coupling member 13 and formed by the
coupling member 13, the closure plate 1 being the closure plate
which is bonded to close one of the concave-convex portion, the
fitting convex portions 61c and 62c are formed in the porous plates
61 and 62, the fitting convex portions 61c and 62c are fitted into
the convex portion of the concave-convex plate, the fitting convex
portions 61c and 62c are supported and fixed by the convex portion
in the midway of the fitting, and thereby the porous plates 61 and
62 are provided in the hollow portion 6.
EXAMPLE 1
[0088] The sound absorbing characteristics were simulated for the
sound absorbing structure body of the first embodiment.
Specifically, as shown in FIG. 1, the parameters were set as
follows. The layer thicknesses d1 and d2 of the partitioned spaces
8 and 9 were 8 mm and 8 mm, the numerical apertures .beta. of the
through holes 11a and 12a of the porous plates 11 and 12 were 1%
respectively, the plate thicknesses t of the porous plates 11 and
12 were 0.3 mm, the hole diameters of the through holes 11a and 12a
were 0.5 mm, the numerical aperture .beta. of the opening 5 was
7.3%, the plate thickness t of the opening 5 was 0.7 mm, and the
hole diameter of the opening 5 was 2 mm. In this case, as shown in
FIG. 9, in addition to the resonance frequency around 1800 Hz, the
sound absorbing structure body has the resonance frequency around
4050 Hz. Compared with the case where the porous plate is not
provided, the sound absorbing structure body of the first
embodiment has a high sound absorption coefficient in a wide range
around a plurality of the frequencies.
EXAMPLE 2
[0089] The sound absorbing characteristics were simulated for a
sound absorbing structure body approximate to the third embodiment.
Specifically, the parameters were set at the same conditions as the
first embodiment. In case where double aluminum foil films are used
as the thin films 42 and 43 of the thin-film sound absorbing body
44, as shown in FIG. 10, a high sound absorption coefficient is
obtained in the range from the resonance frequency around 1950 Hz
to the resonance frequency around 3200 Hz. Compared with the case
where the porous plate is not provided, the sound absorbing
structure body has a high sound absorption coefficient in a
remarkably wide range.
BRIEF DESCRIPTION OF THE DRAWINGS
[0090] FIG. 1 is a schematic diagram of a sound absorbing structure
body;
[0091] FIG. 2 is an exploded perspective view of a sound absorbing
structure body;
[0092] FIG. 3 is a schematic diagram of a sound absorbing structure
body;
[0093] FIG. 4 is a schematic diagram of a sound absorbing structure
body;
[0094] FIG. 5 is a schematic diagram of a sound absorbing structure
body;
[0095] FIG. 6 is an exploded perspective view of a sound absorbing
structure body;
[0096] FIG. 7 is a schematic diagram of a sound absorbing structure
body;
[0097] FIG. 8 is a schematic diagram of a sound absorbing structure
body;
[0098] FIG. 9 is a graph showing sound absorbing
characteristics;
[0099] FIG. 10 is a graph showing sound absorbing
characteristics;
[0100] FIG. 11 is a schematic diagram of a sound absorbing
structure body of a modification;
[0101] FIG. 12 is a schematic diagram of a sound absorbing
structure body of a modification;
[0102] FIG. 13 is a schematic diagram of a sound absorbing
structure body of a modification;
[0103] FIG. 14 is a schematic diagram of a sound absorbing
structure body;
[0104] FIG. 15 is a schematic diagram of a sound absorbing
structure body of a modification;
[0105] FIG. 16 is an exploded perspective view of a sound absorbing
structure body; and
[0106] FIG. 17 is an exploded perspective view of a sound absorbing
structure body.
EXPLANATION OF THE REFERENCE NUMERALS
[0107] 1 closure plate
[0108] 2 concave-convex plate
[0109] 3 convex portion
[0110] 4 concave portion
[0111] 5 opening
[0112] 6 hollow portion
[0113] 11 first porous plate
[0114] 12 second porous plate
[0115] 21 porous plate
[0116] 31 first porous plate
[0117] 41 porous plate
[0118] 51 sound absorbing material
* * * * *