U.S. patent application number 11/629840 was filed with the patent office on 2007-12-27 for sound proofing device and device for conducting a fluid.
This patent application is currently assigned to Geiger Technik Gmbh. Invention is credited to Peter Altenhofen, Matthias Flucht, Uwe Gross, Christoph Heiland.
Application Number | 20070295554 11/629840 |
Document ID | / |
Family ID | 35058065 |
Filed Date | 2007-12-27 |
United States Patent
Application |
20070295554 |
Kind Code |
A1 |
Flucht; Matthias ; et
al. |
December 27, 2007 |
Sound Proofing Device and Device for Conducting a Fluid
Abstract
A device for muffling the sound produced by a fluid in a duct,
especially the sound produced in an intake pipe of a combustion
engine, comprises a wall, whose inside defines a flow passage for
the fluid. The device is at least partly tubular, i.e. it has two
openings. At the outside of the wall (3) is arranged a plurality of
chambers (4), each of which is connected to the flow passage via an
aperture (7). The chambers (4) are bounded by the outside of the
wall (3) as well as by bars (5, 6, 8) formed at the outside of the
wall (3). The chambers (4) function in use as Helmholtz resonators.
In addition, a device for the conduction of a fluid with the sound
proofing device (1) described is presented.
Inventors: |
Flucht; Matthias;
(Eschenlohe, DE) ; Heiland; Christoph; (Wurmansau,
DE) ; Gross; Uwe; (Grafenroda, DE) ;
Altenhofen; Peter; (Garmisch-Partenkirchen, DE) |
Correspondence
Address: |
LOWRIE, LANDO & ANASTASI
RIVERFRONT OFFICE
ONE MAIN STREET, ELEVENTH FLOOR
CAMBRIDGE
MA
02142
US
|
Assignee: |
Geiger Technik Gmbh
Breitenau 1
Garmisch-Partenkirchen
DE
82467
|
Family ID: |
35058065 |
Appl. No.: |
11/629840 |
Filed: |
June 14, 2005 |
PCT Filed: |
June 14, 2005 |
PCT NO: |
PCT/EP05/52756 |
371 Date: |
July 26, 2007 |
Current U.S.
Class: |
181/213 ;
181/212 |
Current CPC
Class: |
F02M 35/1266 20130101;
F02M 35/1261 20130101; F02M 35/1216 20130101 |
Class at
Publication: |
181/213 ;
181/212 |
International
Class: |
F01N 7/00 20060101
F01N007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 16, 2004 |
DE |
10 2004 029 221.3 |
Claims
1-23. (canceled)
24. A device for muffling sound produced by a fluid in a duct, the
device comprising: a wall having an inside surface that defines a
flow passage for the fluid; and a plurality of chambers formed on
at least one exterior surface of the device; wherein the plurality
of chambers are fluidly connected with the flow passage.
25. The device as claimed in claim 24, wherein the at least one
exterior surface comprises a plurality of apertures; and wherein
each chamber of the plurality of chambers is fluidly connected with
the flow passage by at least one aperture of the plurality of
apertures.
26. The device as claimed in claim 25, wherein at least some
chambers of the plurality of chambers have different volumes
relative to one another; and wherein at least some apertures of the
plurality of apertures have different relative cross-sectional
areas relative to one another.
27. The device as claimed in claim 25, wherein the plurality of
chambers and the plurality of apertures are dimensioned so as to
dampen a predetermined frequency range of sound.
28. The device as claimed in claim 24, wherein each chamber of the
plurality of chambers is bounded by an exterior surface of the wall
and by a plurality of defining bars, the bars being formed
extending from the exterior surface of the wall.
29. The device as claimed in claim 28, wherein at least some of the
plurality of defining bars are aligned substantially perpendicular
to a primary flow direction of the fluid.
30. The device as claimed in claim 28, wherein at least some of the
plurality of defining bars are aligned substantially parallel to a
primary flow direction of the fluid.
31. The device as claimed in claim 28, wherein the plurality of
chambers are closed on a side opposite the exterior surface of the
wall.
32. The device as claimed in claim 28, wherein at least some
chambers of the plurality of chambers have an open side opposite
the exterior surface of the wall.
33. The device as claimed in claim 32, wherein the device is
constructed and arranged such that when inserted into the duct, an
area of an inside of an enclosing wall forming the duct covers the
open side of the chambers.
34. The device as claimed in claim 24, wherein the plurality of
chambers form a plurality of Helmholtz resonators.
35. The device as claimed in claim 24, wherein the device is formed
as one piece.
36. The device as claimed in claim 24, wherein the device comprises
a thermoplastic polymer.
37. The device as claimed in claim 36, wherein the thermoplastic
polymer is selected from the group consisting of: polyphenylene
sulphide, a polyamine composite material, a polypropylene composite
material, and polyeurethane.
38. The device as claimed in claim 36, wherein the thermoplastic
polymer comprises a glass fiber fraction.
39. The device as claimed in claim 24, wherein the device comprises
an elastomer.
40. The device as claimed in claim 39, wherein the elastomer
comprises a thermoplastic elastomer.
41. The device as claimed in claim 24, wherein the wall has a
tubular cross-section.
42. The device as claimed in claim 24, wherein the device is
substantially flat; and wherein the wall is arranged in a
plane.
43. The device as claimed in claim 42, further comprising at least
one connecting section, the at least one connecting section being
constructed and arranged such that two adjacent areas of the device
are adjusted to one another at an angle by the at least one
connecting section.
44. The device as claimed in claim 42, wherein the device is a
flexible module.
45. The device as claimed in claim 24, wherein the device is
constructed and arranged to be inserted into a pipe from an outside
of the pipe; and wherein, once the device is inserted into the
pipe, at least a portion of an exterior of the device rests against
an inner wall of the pipe.
46. The device as claimed in claim 45, wherein the pipe is a curved
pipe.
47. The device as claimed in claim 45, wherein the pipe is coupled
to an engine; and wherein the device comprises a connecting unit
that connects the device to a connection point in the engine.
48. A device for conducting fluid, the device comprising: a duct;
and a sound-proofing device disposed within the duct, the
soundproofing device comprising a wall having an interior surface
that defines a flow passage for the fluid, and a plurality of
chambers formed on at least one exterior surface of the wall, the
plurality of chambers being fluidly connected with the flow
passage.
49. The device for conducting fluid as claimed in claim 48, wherein
the device is constructed and arranged to supply air to a
combustion engine.
50. The device for conducting fluid as claimed in claim 48, wherein
the duct comprises a bulge to accommodate the soundproofing device;
and wherein the soundproofing device is disposed within the
bulge.
51. The device for conducting fluid as claimed in claim 48, wherein
a flow cross-section of transition area from the duct to the flow
passage of the soundproofing device is constant.
52. The device for conducting fluid as claimed in claim 48, wherein
a flow cross-section of transition area from the duct to the flow
passage of the soundproofing device changes at a continuous and
constant rate.
Description
[0001] The invention refers to a device for muffling the sound
produced by a fluid in a duct, especially the sound produced in an
intake pipe of a combustion engine. Furthermore, the invention
concerns a device for the conduction of a fluid, especially for the
feeding of air to a combustion engine, comprising a duct.
[0002] Various concepts are known for the damping or suppression of
unwanted noises resulting from the flow of fluids, especially air
or exhaust gases, through piping. On the one hand, it is possible
to form holes in those places in piping at which the standing waves
forming in the pipe have amplitude maxima, such that diversion of
the vibrational energy outwards is possible in order that the
desired damping may be obtained. In this regard, it is made use of
the fact that the engine compartment is usually acoustically well
shielded, such that the diverted vibrations in the engine
compartment continue to be damped and cannot penetrate
outwards.
[0003] Alternatively, it is conceivable to absorb at least part of
the sound directly in the pipe.
[0004] Various acoustic modules for the engine compartment have
been developed for this which are supposed to take account of the
thermal, mechanical and acoustic characteristics. With the known
solutions, however, it has emerged that provisioning and
installation of the modules incur high manufacturing effort, high
material costs and a considerable effort on installation or
conversion, especially when existing systems are retrofitted.
[0005] The object of the invention is therefore to provide a sound
proofing device which permits optimized noise suppression and is
simple to manufacture. Additionally, especially the possibility of
integration into already existing systems is desirable.
[0006] This task is solved by a sound proofing device in accordance
with claim 1 and a device for the conduction of a fluid in
accordance with claim 20.
[0007] The device for muffling the sound produced by a fluid in a
duct, especially the sound produced in an intake pipe of a
combustion engine, comprises a wall, whose inside defines a flow
passage for the fluid. Especially, the sound proofing device has,
on the outside of the wall, a plurality of chambers with which the
flow passage is connected.
[0008] The device mentioned is arranged especially in a duct. The
device may also be suitable for retrofitting noise control to an
already existing duct. Possible ducts would be, for example, a
charge air pipe of a turbocharger, e.g. the intake pipe between the
air filter and a turbocharger, the intake pipe of a combustion
engine, an exhaust gas pipe and the like.
[0009] However, all other possible pipes, for example an exhaust
gas pipe for when a turbocharger is used, can be retrofitted with
the device in accordance with the invention. The sound proofing
device can be used for noise attenuation anywhere in an air
conduction system. Thus, optimum use of the scarce space in the
engine area as well as optimum noise suppression can be achieved
through the compact design of the device.
[0010] Preferably each of the chambers is connected with the flow
passage via at least one aperture. Usually, one aperture is
provided in each case between each chamber and the flow
passage.
[0011] The dimensioning of the chambers is such that the dimensions
are small in relation to the standing wave to be suppressed or
damped.
[0012] The cross-section of the apertures is likewise usually small
in relation to the wavelength of the acoustic wave to be
damped.
[0013] The chambers are bounded preferably from the outside of the
wall as well as by bars formed at the outside of the wall.
[0014] The bars are especially aligned essentially perpendicularly
or parallel to the main flow direction of the fluid. At the
boundary regions of the device, bars may also be provided, which
form a part of enclosing flanges and edge beads, with this type of
bar capable of running in any direction.
[0015] The chambers are provided in order to work as Helmholtz
resonators. Usually, a Helmholtz resonator is a perforated plate,
which is spaced at a distance from a wall, in this case from the
enclosing wall of the duct. This distance of the perforated plate
from the wall corresponds in the present design to the distance
between the enclosing wall of the duct and the wall (of the sound
proofing device) enclosing the flow passage, said enclosing
muffling wall essentially taking on the function of the perforated
plate. This distance in turn essentially corresponds to the height
of the bars. The Helmholtz resonator works like a selective
spring-mass system, which is excited into vibration by the
impinging acoustic waves. Depending on the volume, that is
especially on the length, width and height of the chambers, as well
as on the dimensioning of the apertures, narrow-band damping of the
acoustic waves occurs, since internal losses occur due to the
excitation of vibrations of the Helmholtz resonators. In the case
of resonance, the effect of the Helmholtz resonators is
greatest.
[0016] In a special embodiment, chambers with different volumes
and/or apertures with different aperture cross-sections are
provided. Thus, broadband damping can also be performed across a
wide spectrum. Tuning is thus possible in the frequency band or
frequency range where damping is to occur, especially whether
damping is to occur in one or more narrow spectra, in several
frequency bands or across a large contiguous frequency range is to
be absorbed. This selection can be made by the determination of the
dimension(s) of the chambers.
[0017] Especially, the chambers and/or the apertures can be
dimensioned such that certain frequency ranges of the sound are
selectively absorbed. Through provision of chambers and/or
apertures of varying size, narrow-band frequency ranges are
selectively damped. As a result, a desired noise characteristic can
be produced. Additionally, more frequently occurring resonant
vibrations can be filtered out, i.e. the damping characteristic can
be matched to the excitation spectrum of the engine.
[0018] The device is preferably formed in one piece. As a result,
production and installation are relatively simple and
economical.
[0019] Especially, the device is made from thermoplastic polymer.
In this regard, polyphenylene sulphide (PPS), polyamide composite
material, polypropylene composite material, polyurethane and
similar materials, for example, may be used. The materials may
comprise a glass fiber fraction in order that heat stability and
stability to protracted heat exposure may be increased.
Alternatively, the device may consist also of an elastomer,
especially a thermoplastic elastomer, rubber or india rubber. By
way of simple manufacturing process, an injection moulding method,
for example, would be suitable.
[0020] The wall of the sound proofing device preferably has an
essentially tubular cross-section. Thus, the device is adapted for
introduction or pushing into a pipe, for example into the air feed
pipe. It thereby forms a kind of lining along a certain section of
the pipe.
[0021] The chambers may also be closed to the outside, however.
This means that the chambers are not closed only during insertion
into the pipe, but that an insert with chambers already closed to
the outside is provided.
[0022] Alternatively, at least one part of the chambers has a side
open to the outside. Only during insertion into a pipe are the
chambers closed to the outside by the pipe wall. To this end, the
outside edges of the bars are pressed against the wall of the pipe
and thus more or less close off the chambers. The chambers are then
connected to the environment only via the aperture to the flow
passage.
[0023] The sound proofing device is especially adapted so as to be
inserted into a duct such that an area of the inside of the
enclosing wall of the duct covers the open sides of the chambers.
In the installed state, the chambers thus form closed cavities,
which act as Helmholtz resonators. As already stated, the outside
edges of the bars are pressed against the enclosing wall of the
duct. Perfect contact between all bars and the inside of the
enclosing wall of the duct is not absolutely essential to the
success of the invention.
[0024] The device has a flat shape in one preferred embodiment and,
when the module is not installed, the wall is essentially arranged
in one plane. In this way, production can be simplified still
further. In addition, such a module can be stored in a space-saving
manner.
[0025] The device just described may have at least one connecting
section, which is formed such that at least two adjacent areas of
the device can be adjusted at an angle to each other. During
installation, the flat device must be capable of being rested
against the inside of the duct. This can be effected specifically
by bending points or hinges. Enough connecting sections must be
provided such that satisfactory adjustment of the device to the
shape of the inner wall of the duct is possible. Both plastic and
elastic deformation of the connecting sections are possible.
Insertion in the case of an insert made as a flat part proceeds by
bending the connecting sections to form a jacket section, which
roughly corresponds to the inside of the pipe section into which
the part is to be introduced. Afterwards, the insert is pushed into
the pipe.
[0026] Alternatively the device may be formed as an essentially
flexible module, such as a mat. For example, if the device consists
of an elastomer, then the flat module can be inserted easily into
differently shaped ducts. If it is flexible enough, then curved
pipe sections will not prevent introduction of the insert, which
takes place as described in the last section. The range of
applications of the device as an insert is thereby increased.
Especially, the module may be used like the lining of a section of
the duct fitted with an absorber.
[0027] The device is thus especially intended to be suitable for
insertion into a pipe, especially also into a curved pipe, from the
outside, whereby at least one part of the outside of the device
introduced under application of certain pressure into the pipe
rests against the inner wall of the pipe. This pressure may be
relatively small. It only needs to ensure relatively secure
retention of the device in a pipe, i.e. the outer shape of the
device and the inside of the pipe section that is intended for the
insertion of the device must be matched to one another.
[0028] Furthermore, the device may comprise a connecting unit for
connecting the device to an appropriate connection point in the
engine area. For example, the connecting unit can extend as one
piece to that section of the device intended for muffling. During
insertion, the device is then introduced into a pipe until the
connecting unit protrudes from the opening of the pipe and so
facilitates connection to a further connection point, for example
to the exit of an air filter, the inlet to the turbocharger or a
connecting pipe. The connecting unit can in this way replace a
rubber sleeve, which would otherwise have to be attached
additionally to the opening section of the pipe. Additionally, it
can fulfill sealing functions at connecting sections or serve the
purpose of uncoupling two modules, which otherwise would similarly
require the use of separate parts. This solution arising from the
use of a mono module in accordance with the invention is economical
and assembly of individual components is simple to accomplish.
[0029] The task posed is also resolved by a device for the
conduction of a fluid, especially for the supply of air to a
combustion engine, which device comprises a duct and a sound
proofing device, as described above. The sound proofing device
described above thereby serves especially as an insert for the
duct. The device for the conduction of the fluid may be produced
especially by retrofitting an already existing duct with the sound
proofing device.
[0030] Especially, the duct may be adapted to accommodate the sound
proofing device in a section of the duct.
[0031] The inside of the duct in the area of the section preferably
has a bulge for admitting the sound proofing device. To this end,
for example, a niche may be formed in the duct, into which the
sound proofing device can be inserted. The niche and the design of
the external shape of the sound proofing device may be specifically
matched to each other.
[0032] Especially, the flow cross-section for the fluid in the
transition area from the duct to the flow passage of the sound
proofing device bounded by the wall does not change, or not
substantially, at any rate continuously and not suddenly. A sudden
change in the flow cross-section would have the disadvantage that
the flow resistance for the fluid increases and thus unwanted
energy losses as well as turbulences would arise. Through mutual
adjustment of the duct and the sound proofing device, it is
possible, despite the fitting or retrofitting of a sound proofing
device, to achieve across the entire flow section a more
aerodynamic through-flow cross-section which follows the optimum
contour.
[0033] Further characteristics and advantages of the object of the
invention are apparent from the following description of special
embodiments. These show in
[0034] FIG. 1 a perspective view of a device in accordance with the
invention for muffling;
[0035] FIG. 2 an enlarged representation of a cross-sectional view
of the sound proofing device;
[0036] FIG. 3 the device in accordance with the invention of FIG. 1
in another perspective;
[0037] FIG. 4 an intake pipe with integrated sound proofing device,
partly cut open; and
[0038] FIG. 5 the opening area of the intake pipe with integrated
sound proofing device.
[0039] FIG. 1 shows the device in accordance with the invention for
muffling, designated in the following as sound proofing device 1.
The sound proofing device 1 in the embodiment is a single-piece
insert formed separately from an intake pipe. This has the
advantage that the sound proofing device 1 and the intake pipe of a
combustion engine or a turbocharger, into which the insert is to be
inserted, can be manufactured independently of each other.
Especially, one can easily retrofit an already existing air duct
with an appropriately adapted sound proofing device 1.
Additionally, simple handling of the module during installation as
well as economical production are possible.
[0040] The sound proofing device 1 is preferably made from plastic.
It has been shown that plastic parts can be produced not only
simply and more economically, but that materials also are meanwhile
available which meet the specified mechanical, thermal and acoustic
requirements excellently. For example, the module may consist of
thermoplastics with suitable characteristics regarding wear, heat
resistance and processability. Possible materials may be
polyphenylene sulphide (PPS), polyamide or polypropylene composite
materials, to which a glass fiber fraction may be added where
necessary. An alternative material for the production of the mono
module may be an elastomer.
[0041] The outer shape of the sound proofing device 1 is
essentially determined by the formation of the section of a
pipe/pipe into which the sound proofing device 1 is to be inserted.
Especially, the outer shape of the sound proofing device 1 can be
adapted to already existing pipes, such that the pipes can be
retrofitted with the sound proofing device 1.
[0042] The front side of the sound proofing device 1 in the present
embodiment has an essentially circular aperture 2 with a diameter
d, which is bounded by the flange 8. The diameter d may correspond
thereby to the diameter of an outlet opening of an air filter or
the diameter of a pre-positioned or connecting duct section in
order that losses due to flow resistance may be avoided if
possible. Altogether, the influence of the sound proofing device 1
on the flow and thus the pressure loss along the flow path are to
be minimized.
[0043] The flow passage for the air or the exhaust gases connected
to opening 2 is bounded by a wall 3. When a fluid, for example air
or exhaust gas, is flowing through the sound proofing device 1, the
inside of the wall 3 of the sound proofing device 1 can act as
resonator, whereby standing acoustic waves may form. In order that
sound suppression and/or muffling may be achieved, the sound
proofing device 1 has a plurality of chambers 4, which are bounded
by the outside of the wall 3 as well as by radial bars 5 and by
bars 6 perpendicular to it and running in a longitudinal direction.
As is clear from FIG. 1, the bars 5, 6 form a kind of lattice
structure on the outside surface of the wall 3. The chambers 4 are
open to the outside in insert 1, but during insertion into the
intake pipe are closed by its enclosing wall from the outside, such
that defined cavities are created. The chambers 4 can act then as
Helmholtz resonators to attenuate the noise. Alternatively,
however, chambers 4 already closed to the outside could be formed
in the sound proofing device 1.
[0044] Each of the chambers 4 is connected with the interior of the
sound proofing device via an aperture 7. This is clear from FIG.
2.
[0045] With the aid of FIG. 2, which shows an enlarged
cross-sectional view of the sound proofing device 1, the mechanism
of the sound proofing device will be explained.
[0046] Each of the chambers 4 forms a cavity, which is bounded by
the outside surface of the wall 3 as base surface and by the bars
5, 6. The volume of the cavities is determined by the spacing of
the bars 5, 6 as well as their height. The cavities are connected
with aperture 7 to the interior, i.e. to the flow passage, of the
sound proofing device 1. The cavities then act as Helmholtz
resonators when the sound proofing device has been inserted. Air
does not usually flow through the chambers 4 themselves. Even
during manufacture, the chambers 4 can be alternatively made as
outwardly closed cavities of the sound proofing device 1.
[0047] The absorption frequency of a Helmholtz resonator
essentially depends on the size of the chambers 4 as well as on the
dimensioning of the apertures 7. In this way, certain frequency
bands can be selectively damped. This offers the possibility of
selecting and tuning the noise characteristic of the frequency
spectrum not absorbed by the sound proofing device. On the other
hand, via the arrangement of different cross-sections of the
apertures 7 and/or by the use of different-sized chambers 4,
damping can be performed across a broad band in order that muffling
may be as complete as possible. The wall 3 of sound proofing device
1 with apertures 7 essentially forms a circularly curved perforated
plate, which is arranged at a certain distance from the inner wall
of the duct in which sound proofing device 1 is to be arranged. The
distance is thereby determined substantially by the height of the
bars 5, 6. In the operating state, each of the Helmholtz resonators
acts in a narrow band through excitation of vibrations, which
generate internal losses. The damping effect of the Helmholtz
resonators is greatest in the case of resonance. The parameters
determining resonance volume, namely height, width and depth of the
resonance chambers 4, are smaller in this regard than the
wavelengths of the acoustic waves to be absorbed.
[0048] FIG. 3 shows the sound proofing device in accordance with
the invention 1 from another perspective. The second opening 12 of
the flow passage of the sound proofing device 1, which in the
illustration in FIG. 1 points into the plane of the page, is
bounded by a second flange 11.
[0049] In the present case, the sound proofing device is formed
and/or its openings are arranged such that the sound proofing
device can be inserted in the area of a duct bend. The gases
entering the first opening 2 flow through the flow passage bounded
by the wall 3 and exit the sound proofing device 1 again through
the second opening 12 in one or more directions R2, other than the
inflow direction R1. The invention is not to be restricted,
however, to this embodiment, but, for example, also definitely
comprises sound proofing devices with constant flow direction of
the fluid.
[0050] FIG. 4 shows a cross-sectional view of an intake pipe 9,
which has a section 10, in which, as shown in FIG. 1, a sound
proofing device 1 is arranged. The bulge in section 10 is caused by
the provision of an additional cavity extending beyond the average
flow cross-section of the intake pipe 9, into which cavity the
sound proofing device 1 is inserted. The section 10 of the intake
pipe 9 and the sound proofing device 1 are matched in terms of
shape to each other such that the sound proofing device 1 can be
inserted precisely into the cavity provided in addition to the flow
volume. The diameter d (see FIG. 1) of the flow passage of the
sound proofing device 1 is just as large in this regard as the
inside diameter of the pipe section which connects in area 10' to
section 10. The same applies to the other opening of the sound
proofing device in area 10''. As a result, an increase in flow
resistance is prevented relative to an intake pipe not equipped
with a sound proofing device. The flow passage of the sound
proofing device 1 can therefore aerodynamically follow the contours
of the flow cross-section of the intake pipe in the transition
areas 10', 10'', whereby, in the case of retrofitting as well, an
aerodynamic, space-saving as well as simple and economically
manufacturable solution is provided.
[0051] The sound proofing device 1 is safely held in its service
position by contact of the flange 8 with a catch of the intake pipe
9 as well as by contact with a second catch in the area of the rear
aperture.
[0052] Especially, the intake pipe 9 is an air-intake pipe between
air filter and turbocharger. The invention is not restricted,
however, to this application. Rather, the sound proofing device in
accordance with the invention can be used in all possible pipes
through which a fluid, for example air or exhaust gas, flows. For
example, the exhaust gas pipe of a combustion engine can also be
fitted with the sound proofing device in accordance with the
invention 1.
[0053] The intake pipe 9 can be manufactured from a suitable
plastic. In principle, a one-piece design of the sound proofing
device 1 with the intake pipe 9 is also conceivable.
[0054] FIG. 5 shows the opening area of the intake pipe 9 with
inserted sound proofing device. The apertures 7 of the sound
proofing device 1 connect the flow passage of the sound proofing
device 1 with the chambers 4 behind it, which work as Helmholtz
resonators. In the present example, the sound proofing device 1 is
arranged in the region of a bend in the pipe. The sound proofing
device 1 can, however, in the context of the invention, extend into
any area of the intake pipe 9 and across any section 10.
* * * * *