CN207540116U - Silencer - Google Patents

Abstract

The utility model discloses a kind of silencer, including：Housing, housing are cylindrical in shape and limit cavity closed at both ends, and housing has air inlet and air outlet, and air inlet and air outlet are located on the peripheral wall of housing；First partition, first partition is located in cavity, air inlet is opposite with the side of first partition, air outlet is opposite with the opposite side of first partition, and both ends of the first partition on shell length direction are first end and second end, and air-flow is after air inlet entrance, a part of air-flow flows out after bypassing first end from air outlet, the channel that the fraction flows through is the first gas channel, and another part air-flow flows out around second end from air outlet, and the channel which flows through is the second gas channel.Silencer according to the present utility model by setting first partition structure in housing, defines the flow trace of air-flow, air-flow shunts expansion decompression by first partition, reduced velocity flow stroke increases, convenient for the processing to noise so that pneumatic noise is effectively weakened.

Description

Silencer

Technical field

The utility model is related to a kind of silencers.

Background technology

Ventilation silencer is mainly the following, straight pipe type, drum type brake, pore type and spiral, straight pipe type silencer Acoustic attenuation performance is stablized, and resistance is small, but is only suitable for relatively low air quantity, and when air quantity is larger, noise elimination is decreased obviously.Drum type brake silencer is fitted For larger air quantity, but windage is larger, and when air quantity is more than to a certain degree, noise elimination effect declines.Microperforated panel silencer and spiral Formula silencer, noise elimination effect is preferable, but process and structure is all complex, and windage is big.Above several silencer air-flows are towards one A direction flowing, air flow rate is relatively fast, and kinetic energy rejection is larger when air-flow discharges silencer.

Utility model content

The utility model is intended at least solve one of technical problem in the prior art.For this purpose, the utility model carries Go out a kind of silencer, the silencer increases the stroke of air-flow flowing, has preferable noise elimination effect.

According to the silencer of the utility model embodiment, including：Housing, the housing are cylindrical in shape and limit closed at both ends Cavity, the housing have air inlet and air outlet, the air inlet and air outlet are located on the peripheral wall of the housing；First Partition board, the first partition are located in the cavity, and the air inlet is opposite with the side of the first partition, the air outlet Opposite with the opposite side of the first partition, both ends of the first partition on the shell length direction are first end and the Two ends, air-flow is after air inlet entrance, and a part of air-flow flows out after bypassing the first end from the air outlet, the part The channel that air-flow flows through is the first gas channel, and another part air-flow flows out around the second end from the air outlet, the portion It is the second gas channel to divide the channel that air-flow flows through.

According to the silencer of the utility model embodiment, by setting first partition structure in housing, air-flow is defined Flow trace, air-flow by first partition shunt expansion decompression, reduced velocity flow stroke increase, convenient for the processing to noise, make Pneumatic noise is obtained effectively to be weakened.

Some embodiments according to the present utility model, the wall surface opposite with the first end is the first wall on the housing Face, the wall surface opposite with the second end is the second wall surface on the housing, in first wall surface and second wall surface At least one is arcwall face, and the arcwall face is protruded towards the external of the cavity.

In some embodiments according to the present utility model, first gas channel and second gas channel at least The first sound absorption portion is equipped in one.

Further, the first sound absorption portion is porous foams shape part.

In some embodiments of the utility model, the silencer further includes metal net mask, the first sound absorption portion It is limited in the metal net mask.

In some embodiments of the utility model, the first sound absorption portion is equipped at the first end and the second end.

Some embodiments according to the present utility model, be equipped at the position of the air outlet in the cavity second every Plate, the second partition are suitable for first gas channel and second gas channel being directed to the air outlet.

Further, the second partition is arc panel.

In some embodiments of the utility model, the second partition is two, one end of two second partitions Connection and extend towards the air outlet, the separate direction extension to each other of the other ends of two second partitions, two described the It is limited between two partition boards and holds chamber, the intracavitary that holds is equipped with the second sound absorption portion.

Some embodiments according to the present utility model, the silencer further include multiple third partition boards being interspersed, There is the third partition board, air-flow is around described at least one of first gas channel and second gas channel Third partition board flows to the air outlet.

Further, there are multiple through-holes on the third partition board.

Further, the percent opening on the third partition board is 10%-20%.

Optionally, the aperture of the through-hole is 4-6mm.

Some embodiments according to the present utility model, at least one of first gas channel and the second gas channel At least part inner wall on be coated with noise reduction layer.

Preferably, the thickness of the noise reduction layer is 40-60mm.

Description of the drawings

The above-mentioned and/or additional aspect and advantage of the utility model will in the description from combination accompanying drawings below to embodiment Become apparent and be readily appreciated that, wherein：

Fig. 1 is the structure diagram according to the silencer of the utility model embodiment；

Fig. 2 is the structure diagram according to the silencer of the utility model another embodiment.

Reference numeral：

Silencer 100,

Housing 1, air inlet 11, import air hose 12, suction flange 13,

Air outlet 14, outlet air hose 15, outlet(discharge) flange 16,

First partition 2, the first gas channel 21, the second gas channel 22,

First sound absorption portion 23, first end 24, second end 25,

Second partition 3, the second sound absorption portion 31, holds chamber 32,

Third partition board 4, the first wall surface 5, the second wall surface 6, metal net mask 7.

Specific embodiment

The embodiment of the utility model is described below in detail, the example of the embodiment is shown in the drawings, wherein from beginning Same or similar element is represented to same or similar label eventually or there is the element of same or like function.Below by ginseng The embodiment for examining attached drawing description is exemplary, and is only used for explaining the utility model, and it is not intended that the utility model Limitation.

In the description of the present invention, it is to be appreciated that term " length ", " thickness ", " on ", " under ", " left side ", The orientation or position relationship of the instructions such as " right side ", " interior ", " outer " are based on orientation shown in the drawings or position relationship, merely to just In description the utility model and simplified description rather than instruction or imply that signified device or element must be with specific sides Position, with specific azimuth configuration and operation, therefore it is not intended that limitation to the utility model.In addition, define " first ", One or more this feature can be expressed or be implicitly included to the feature of " second ".In the description of the present invention, Unless otherwise indicated, " multiple " are meant that two or more.

In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, term " is pacified Dress ", " connected ", " connection " should be interpreted broadly, for example, it may be being fixedly connected or being detachably connected or integrally Connection；Can be mechanical connection or electrical connection；It can be directly connected, can also be indirectly connected by intermediary, It can be the connection inside two elements.For the ordinary skill in the art, can above-mentioned art be understood with concrete condition Concrete meaning of the language in the utility model.

Below with reference to Fig. 1-Fig. 2 descriptions according to the silencer 100 of the utility model embodiment.

As depicted in figs. 1 and 2, according to the silencer of the utility model embodiment 100, including：Housing 1 and first partition 2.

As shown in Figure 1, housing 1 is cylindrical in shape and limits cavity closed at both ends, housing 1 has air inlet 11 and air outlet 14, air inlet 11 and air outlet 14 are located on the peripheral wall of housing 1.For example, as shown in Figure 1, housing 1 is one closed at both ends, it is interior Portion is the tubular structure of cavity, and the upper perimeter wall (upper end as shown in Figure 1) of housing 1 is equipped with air inlet 11, the lower peripheral wall of housing 1 It is set on (lower end as depicted) there are one air outlet 14, air inlet 11 is located at air outlet 14 on same axis.Housing 1 is set Count into tubular structure so that air-flow can flow through shell with decompression expansion after air inlet 11 enters housing 1 so as to reduce air-flow The speed of body 1 provides the time for noise elimination processing.

As depicted in figs. 1 and 2, first partition 2 is located in cavity, and air inlet 11 is opposite with the side of first partition 2, outlet air Mouth 14 is opposite with the opposite side of first partition 2, and both ends of the first partition 2 on 1 length direction of housing are first end 24 and second End 25, air-flow is after the entrance of air inlet 11, and a part of air-flow flows out after bypassing first end 24 from air outlet 14, the fraction stream The channel crossed is the first gas channel 21, and another part air-flow flows out around second end 25 from air outlet 14, the fraction stream The channel crossed is the second gas channel 22.First partition 2 is set, the stroke that air-flow flows in housing 1 is increased, in a constant current In the case of amount, flowing time of the air-flow in housing 1 is increased.

According to the silencer 100 of the utility model embodiment, by setting 2 structure of first partition in housing 1, define The flow trace of air-flow, air-flow shunt expansion decompression by first partition 2, and reduced velocity flow stroke increases, convenient for the place to noise Reason so that pneumatic noise is effectively weakened.

Some embodiments according to the present utility model, as depicted in figs. 1 and 2, the wall surface opposite with first end 24 on housing 1 For the first wall surface 5, the wall surface opposite with second end 25 is the second wall surface 6 on housing 1, in the first wall surface 5 and the second wall surface 6 extremely Few one is arcwall face, and arcwall face is protruded towards the external of cavity.For example, as shown in Figure 1, the first wall surface 5 is located at a left side for housing 1 Side one end (left end as shown in Figure 1), the second wall surface 6 are located at right side one end (right end as shown in Figure 1) of housing 1, the first wall 5 and second wall surface 6 of face is the arcwall face that arc faces outwardly protrusion.It is by least one of the first wall surface 5 and the second wall surface 6 Arcwall face, the flow resistance of arcwall face is smaller, while air current flow direction is changed air-flow can be reexpanded Decompression reduces the noise of air-flow.

Some embodiments according to the present utility model, as depicted in figs. 1 and 2, the first gas channel 21 and the second air-flow are led to The first sound absorption portion 23 is equipped at least one of road 22.The first sound absorption portion 23, air-flow stream are set in the channel of air-flow flowing Through the first sound absorption portion 23, noise can be weakened by a degree of absorb.

Further, as depicted in figs. 1 and 2, the first sound absorption portion 23 can be porous foams shape part.Porous foams The percent opening height of shape material, good permeability, compression strength are high, and to air-flow while having preferable sound absorption effect, air-flow flows through Windage be unlikely to excessive.

In some embodiments of the utility model, as depicted in figs. 1 and 2, silencer 100 further includes metal net mask 7, the One sound absorption portion 23 is limited in metal net mask 7.The first sound absorption portion 23 can be limited at gold under the blowing of air-flow as a result, Belong in guard 7, metal net mask 7 has the function of to fix the first sound absorption portion 23.

In some embodiments of the utility model, as depicted in figs. 1 and 2, it is equipped at first end 24 and second end 25 First sound absorption portion 23.Since air-flow is after import air hose 12 enters housing 1, partly can housing be flowed through by the first gas channel 21 1 first end 24 moves to outlet air hose 15, and rest part can be moved by the second air-flow by flowing through the second end 25 of housing 1 To outlet air hose 15, the first sound absorption portion 23 is respectively provided in first end 24 and second end 25, the air-flow for flowing through housing 1 either flows through The sound absorption that the first end 24 or second end 25 of housing 1 can pass through the first sound absorption portion 23 is handled, the effect that noise is weakened More preferably.

Some embodiments according to the present utility model, as depicted in figs. 1 and 2, in cavity at the position of air outlet 14 Equipped with second partition 3, second partition 3 is suitable for the first gas channel 21 and the second gas channel 22 being directed to air outlet 14.The One main function of two partition boards 3 be will move to air outlet 14 air-flow guide to outlet air hose 15, avoid at air outlet 14 It gives birth to and disturbs because of air-flow counter current flow movable property, and then influence the kinetic energy of air-flow.

Further, as depicted in figs. 1 and 2, second partition 3 is arc panel.Second partition 3 is designed to arc panel, Flow perturbation loss kinetic energy is reduced first, can change the direction of motion of air-flow and air-flow is allowd to smoothly pass, the second is increasing Add the resistance drop low flow velocity of movement, improve sound absorption effect.

In some embodiments of the utility model, as depicted in figs. 1 and 2, second partition 3 be two, two second every One end connection of plate 3 and extend towards air outlet 14, the separate direction extension to each other of the other ends of two second partitions 3, two It is limited between a second partition 3 and holds chamber 32, held and the second sound absorption portion 31 is equipped in chamber 32.For example, as shown in Figure 1, setting Two 3 structures of second partition, the second partition 3 of left side (left end as shown in Figure 1) can will in the first gas channels 21 Air-flow is guided to the outlet air hose 15 of downside, and the second partition 3 of right side (right end as shown in Figure 1) can be by the first gas channel Air-flow in 21 is guided to the outlet air hose 15 of downside, the gas in air-flow and the second gas channel 22 in the first gas channel 21 At air outlet 14 convection current will not occur under the guiding of second partition 3 for stream, reduce the loss of airflow kinetic energy to the greatest extent. In addition, the second sound absorption portion 31 is placed in chamber 32 in two holding for second partition 3, to noise before air-flow enters outlet air air hose Further sound absorption processing is made.

Some embodiments according to the present utility model, as shown in Fig. 2, silencer 100 further include it is multiple be interspersed Three partition boards 4, have third partition board 4 at least one of the first gas channel 21 and the second gas channel 22, and air-flow is around the Three partition boards 4 flow to air outlet 14.Original gas channel can be divided into several small spaces by third partition board, increased air-flow and existed Flowing stroke in housing 1 further increases run duration of the air-flow in housing 1, ensure that silencer 100 to pneumatic noise Processing time.

Further, as shown in Fig. 2, having multiple through-holes on third partition board 4.Multiple through-holes can reduce air-flow and flow through third Flow resistance during a partition board reduces third 4 loss to airflow kinetic energy of partition board.

Further, as shown in Fig. 2, the percent opening on third partition board 4 is 10%-20%.For example, as shown in Fig. 2, setting Multiple third partition boards 4, the percent opening of each third partition board 4 are not intended to limit identical, in the range of maintaining 10%-20%, make It obtains the inlet end in each small space separated by third partition board 4 and the volume of outlet side differs, air-flow can be sent out in the process Raw noise consumable declines.

Optionally, as shown in Fig. 2, the aperture of through-hole is 4-6mm.Aperture is excessive so that air-flow can only pass through third partition board 4 Through-hole enter next space, mass motion formation will not increase, and when aperture is too small because the resistance in aperture is excessive, air-flow It only can be above or below third partition board 4 to next spatial movement so that the volume in each small space is identical, will not occur Compression process is expanded, noise consumable effect can not occur, therefore selected more suitable 4-6mm through-hole aperture sizes.

Some embodiments according to the present utility model, as depicted in figs. 1 and 2, the first gas channel 21 and the second air-flow are led to Noise reduction layer is coated at least part inner wall at least one of road 22.Noise reduction layer has certain erasure effect, air-flow stream After noise reduction layer, the noise in air-flow can effectively be weakened.

Preferably, as depicted in figs. 1 and 2, the thickness of noise reduction layer is 40-60mm.The sound absorption effect and noise reduction layer of noise reduction layer Thickness have compared with Important Relations, the consumption of economy and noise reduction layer thickness to airflow kinetic energy is considered, using the noise reduction of 40-60mm thickness Layer, while preferable sound absorption effect is ensured, the consumption of maximum control cost and noise reduction layer to airflow kinetic energy.

Below with reference to Fig. 1-Fig. 2 descriptions according to the silencer 100 of the utility model specific embodiment.It is worth understanding, Described below is exemplary, it is intended to for explaining the utility model, and it is not intended that limitation to the utility model.

Embodiment one

As shown in Figure 1, the silencer 100 of the present embodiment, including：Housing 1, the first wall surface 5, the second wall surface 6, first partition 2nd, second partition 3 and metal net mask 7.

As shown in Figure 1, housing 1 is the tubular structure that inside is cavity, housing 1 is located at the center of silencer 100.Housing 1 Left side one end connect with the first wall surface 5, right side one end of housing 1 is connect with the second wall surface 6.The upper perimeter wall of housing 1 be equipped with into Air port 11 and import air hose 12, import air hose 12 are connected with the air inlet 11 of housing 1, in the company of import air hose 12 and air inlet 11 The place of connecing is also equipped with suction flange 13.The lower peripheral wall of housing 1 is equipped with air outlet 14 and outlet air hose 15, exports air hose 15 and housing 1 air outlet 14 connects, and outlet(discharge) flange 16 is also equipped in outlet air hose 15 and the junction of air outlet 14.Flange arrangement can be with The bonding strength of import air hose 12 and air inlet 11 (or outlet air hose 15 and air outlet 14) and the leakproofness of junction are improved, The diameter of this outer vent air hose is greater than the diameter of import air hose, reduces the resistance of exit air-flow flowing, and then reduces The loss of kinetic energy.

As shown in Figure 1, the first wall surface 5 and the second wall surface 6 are arcwall face, arcwall face is protruded towards the outside of 1 cavity of housing. First wall surface 5 and housing are provided with metal net mask 7 between 1 left side one end, between the second wall surface 6 and right side one end of housing 1 It is provided with 7 structure of metal net mask.Porosity is provided in first wall surface 5, the second wall surface 6 and the arc-shaped cavity of metal net mask 7 First sound absorption portion 23 of foam-like, the first sound absorption portion 23 of porous foams shape have preferable sound absorption, can be effectively Reduce the noise of air-flow.

As shown in Figure 1, housing 1 is internally provided with first partition 2, left side one end along 1 length direction of housing is the One end 24, right side one end are second end 25.After air-flow is entered by the air inlet 11 of housing 1, a part around after first end 24 from Air outlet 14 flows out, and the channel which flows through is the first gas channel 21, and another part air-flow can bypass second end 25 It is flowed out from air outlet 14, the channel that this fraction flows through is the second gas channel 22.After setting first partition 2, air-flow needs Could be flowed out around first end 24 or second end 25 from air outlet 14, increase air-flow flowing stroke, in addition, setting first every Air-flow needs are flowed through from the first sound absorption portion 23 equipped with porous foams shape after plate 2, play the role of noise elimination.

As shown in Figure 1, second partition 3 there are two being also set up at the position of close air outlet 14 in the cavity of housing 1, two One end of a second partition 3 towards air outlet 14 links together, the other end separate direction extension to each other.Two second every Plate 3, which defines, holds chamber 32, holds the second sound absorption portion 31 being provided in chamber 32 for noise elimination, the second sound absorption portion 31 is filled with Porous foams shape sound-absorbing material.

As shown in Figure 1, it is both provided with disappearing for 40-60mm thickness on the inner wall of housing 1, first partition 2 and second partition 3 Sound-absorbing layer.The material of noise reduction layer is polyurethane foam, by the noise reduction layer for setting polyurethane foam so that air-flow is during the motion It is contacted with noise reduction layer, is absorbed the noise of part, improve noise elimination effect.

As shown in Figure 1, from the point of view of the track of air-flow flowing, air-flow first passes through import air hose 12 and flange enters on housing 1 The air inlet 11 of peripheral wall, into the air-flow of air inlet 11, expansion decompression simultaneously shunts, and fraction is flowed along the first gas channel 21 It is dynamic, it can be with the noise reduction on 1 inner wall of housing and first partition 2 of the first gas channel 21 in 21 flow process of the first gas channel Layer contact so that noise in air-flow is by partial reduction, and air-flow can be across the in flow process in the first gas channel 21 First sound absorption portion 23 of one wall surface 5 and the porous foams shape in metal net mask 7, so as to which there is air-flow in the first sound absorption portion 23 into one The noise elimination processing of step, air-flow can also expand decompression and 180 degree divertical motion again while the first wall surface 5 are entered, with Enter the second partition 3 at air outlet 14 afterwards, air-flow flows through second partition 3, the second sound absorption of sound absorption portion in two second partitions 3 31 can further absorb the noise in air-flow, and under the guide functions of second partition 3, air-flow moves to outlet along air outlet 14 Air hose 15, thereafter lets out.

The second gas channel 22 is flowed through with remaining corresponding air-flow of this fraction to flow out from air outlet 14, is moved through Journey is similar with the air motion process in the first gas channel 21, is only the direction of motion in some positions on the contrary, not doing here It is discussed in detail.

The silencer 100 of the present embodiment by setting 2 structure of first partition in housing 1, defines the flowing rail of air-flow Mark, air-flow shunt expansion decompression by first partition 2, and reduced velocity flow stroke increases, convenient for the processing to noise so that air-flow is made an uproar Sound is effectively weakened.

Embodiment two

The present embodiment is roughly the same with the structure of embodiment one, wherein identical component uses identical reference numeral, such as Shown in Fig. 2, it the difference is that only that silencer 100 further includes third partition board 4.As shown in Fig. 2, the first gas channel 21 and second Multiple inclined third partition boards 4 are both provided in gas channel 22, air-flow is in the first gas channel 21 or the second gas channel 22 Fraction needs, around third partition board 4, then to move to air outlet 14 during interior movement.

As shown in Fig. 2, multiple third partition boards 4 by original airway segmentation into several small spaces, offered on third partition board 4 Multiple through-holes, the percent opening of each partition board is in 10%-20%, aperture 4-6mm, through-hole structure air-flow less to a certain extent The resistance of movement.

As shown in Fig. 2, inclined third partition board 4 is set so that the volume flowed into and out of the air-flow in each small space It differs, on the other hand most of air-flow needs to move around third partition board 4.Under the collective effect of the two, most air-flow (primary air) can be Jing Guo expansion-compression-expansion process, the energy of primary air noise can be consumed, while by the pair of through-hole Air-flow is because different with the movement locus of primary air, it may occur that collision generates flow-disturbing vortex etc., also increases disappearing for noise energy Consumption.

The silencer 100 of the present embodiment, by setting third partition board 4 in silencer 100 so that air-flow is in silencer Flowing stroke in 100 increases, and primary air can undergo the process of expansion-compression-expansion, the energy meeting of noise during the motion Largely consumed.

In the description of this specification, reference term " one embodiment ", " some embodiments ", " illustrative examples ", The description of " example ", " specific example " or " some examples " etc. means to combine specific features, the knot that the embodiment or example describe Structure, material or feature are contained at least one embodiment or example of the utility model.In the present specification, to above-mentioned art The schematic representation of language may not refer to the same embodiment or example.Moreover, description specific features, structure, material or Person's feature can in an appropriate manner combine in any one or more embodiments or example.

While there has been shown and described that the embodiment of the utility model, it will be understood by those skilled in the art that： In the case of the principle and objective for not departing from the utility model can these embodiments be carried out with a variety of variations, modification, replaced And modification, the scope of the utility model are limited by claim and its equivalent.

Claims (15)

1. a kind of silencer, which is characterized in that including：

Housing, the housing are cylindrical in shape and limit cavity closed at both ends, and the housing has air inlet and air outlet, described Air inlet and air outlet are located on the peripheral wall of the housing；

First partition, the first partition are located in the cavity, and the air inlet is opposite with the side of the first partition, institute State that air outlet is opposite with the opposite side of the first partition, both ends of the first partition on the shell length direction are the One end and second end, after air inlet entrance, a part of air-flow bypasses after the first end from the air outlet stream air-flow Go out, the channel which flows through is the first gas channel, and another part air-flow bypasses the second end from the air outlet Outflow, the channel which flows through are the second gas channel.

2. silencer according to claim 1, which is characterized in that the wall surface opposite with the first end is on the housing First wall surface, the wall surface opposite with the second end is the second wall surface, first wall surface and second wall on the housing At least one of face is arcwall face, and the arcwall face is protruded towards the external of the cavity.

3. silencer according to claim 1, which is characterized in that first gas channel and second gas channel At least one of in be equipped with the first sound absorption portion.

4. silencer according to claim 3, which is characterized in that the first sound absorption portion is porous foams shape part.

5. silencer according to claim 3, which is characterized in that further include metal net mask, the first sound absorption portion is limited It is scheduled in the metal net mask.

6. silencer according to claim 3, which is characterized in that be equipped with first at the first end and the second end Sound absorption portion.

7. silencer according to claim 1, which is characterized in that set at the position of the air outlet in the cavity There is second partition, the second partition is suitable for first gas channel and second gas channel being directed to the outlet air Mouthful.

8. silencer according to claim 7, which is characterized in that the second partition is arc panel.

9. silencer according to claim 7, which is characterized in that the second partition be two, two described second every One end connection of plate and extend towards the air outlet, the separate direction extension to each other of the other ends of two second partitions, two It is limited between a second partition and holds chamber, the intracavitary that holds is equipped with the second sound absorption portion.

10. silencer according to claim 1, which is characterized in that multiple third partition boards being interspersed are further included, it is described There is the third partition board, air-flow bypasses the third at least one of first gas channel and second gas channel Partition board flows to the air outlet.

11. silencer according to claim 10, which is characterized in that there are multiple through-holes on the third partition board.

12. silencer according to claim 11, which is characterized in that the percent opening on the third partition board is 10%- 20%.

13. silencer according to claim 11, which is characterized in that the aperture of the through-hole is 4-6mm.

14. silencer according to claim 1, which is characterized in that in first gas channel and the second gas channel At least one at least part inner wall on be coated with noise reduction layer.

15. silencer according to claim 14, which is characterized in that the thickness of the noise reduction layer is 40-60mm.