sound attenuating trim piece comprising at least one insulating area with acoustic mass-spring chara

专利摘要:
SOUND Attenuator TRIM PIECE INCLUDING AT LEAST ONE INSULATING AREA WITH ACOUSTIC MASS-SPRING CHARACTERISTICS INCLUDING AT LEAST ONE LAYER OF MASS AND AN UNCOUPLING LAYER ADJACENT TO THE MASS LAYER AND USE OF A SOUND LAYER AS A TRIMMING PIECE COMBINED INSULATION AND ABSORBENT A sound-attenuating trim piece, comprising at least one insulating area with an acoustic spring-mass characteristic comprising at least one mass layer and a decoupling layer adjacent to the mass layer, by means of which the mass layer mass consists of a porous fibrous layer and a barrier layer, with the barrier layer being positioned between the porous fibrous layer and the uncoupling layer and all layers are laminated together, and whereby the porous fibrous layer at least in the insulating area is having an adjusted dynamic Young's modulus (Pa) such that the radiation frequency is at least 3000 (Hz).
公开号:BR112013019385B1
申请号:R112013019385-9
申请日:2011-03-09
公开日:2021-05-18
发明作者:Claudio Bertolini；Claudio Castagnetti；Marco SEPPI
申请人:Autoneum Management Ag；
IPC主号:

专利说明:

technical field
[001] The present invention relates to an automotive trim part to attenuate noise in a vehicle. Fundamentals of technique
[002] The sources of noise in a vehicle are many and include, but are not limited to, power train, transmission, adhesive tire contact area (stimulated by the road surface), brakes, and wind. The noise generated by all these sources within the vehicle cabin covers a slightly higher frequency range which, for normal diesel and petroleum vehicles, can increase by up to 6.3kHz (above this frequency, the acoustic power radiated by the noise sources in a vehicle is generally neglected). Vehicle noise is generally divided into low, medium and high frequencies. Typically, low frequency noise can be considered to cover the frequency range between 50Hz and 500Hz and is dominated by “structure-support” noise: vibration is transmitted to the panels surrounding the passenger cabin through a variety of structural pathways and such panels then radiate noise into the cabin itself. On the other hand, typically high frequency noise can be considered to cover the frequency range above 2kHz. High-frequency noise is typically dominated by “air-borne” noise: in this case the transmission of vibration to the panels surrounding the passenger cabin takes place via air transport pathways. It is recognized that there is a gray area where the two effects are combined and neither dominates. However, for passenger comfort, it is important that noise is attenuated in the mid-frequency range as well as in the low and high frequency ranges.
[003] To attenuate noise in vehicles such as cars and trucks the use of insulators, absorbers and absorbers to reflect and dissipate sound and thus reduce the final interior sound level is well known.
[004] Insulation is traditionally achieved through a "mass-spring" barrier system, whereby the mass element is formed by a layer of high-density impenetrable material normally designed as a heavy layer and the spring element is formed by a layer of low-density material such as uncompressed felt or foam.
[005] The name "spring-mass" is commonly used to define a barrier system that provides sound isolation by combining two elements, called "mass" and "spring". A part or device is said to work as a “spring mass” if its physical behavior can be represented by the combination of a mass element and a spring element. An ideal mass-spring system acts as a sound insulator mainly thanks to the characteristics of its elements, which are joined together.
[006] A spring-mass system is normally placed inside a car on a layer of steel, with the spring element in contact with the steel. If considered as a whole, the complete system (mass-spring plus steel layer) has the characteristics of a double partition. The loss insertion is a quantity that describes how effective the action of the spring-mass system is when placed over the steel layer, regardless of the insulation provided by the steel layer itself. Its insertion loss shows the insulation performance of the spring-mass system.
[007] The theoretical insertion loss curve (IL, measured in dB) that characterizes a spring-mass system has in particular the following aspects. Over most of the frequency range, the curve increases with frequency in an approximately linear fashion, and the growth rate is around 12dB/octave; such a linear trend is considered to be very effective in ensuring good insulation against incoming sound waves and, for this reason, spring-mass systems have been widely used in the automotive industry. This tendency is only achieved above a certain frequency value, called the “spring-mass system resonant frequency”, at which the system is not effective as a sound insulator. The resonance frequency depends mainly on the weight of the mass element (the higher the weight, the lower the resonance frequency) and on the stiffness of the spring (the higher the stiffness, the higher the resonance frequency). At the resonant frequency of the spring-mass system, the spring element transmits the vibration of the underlying structure to the mass element in a very efficient way. At this frequency, the vibration of the mass element is even higher than that of the underlying structure, and thus the noise radiated by the mass element is even higher than that which would be radiated by the underlying structure without a spring-mass system. As a consequence, around the resonant frequency of the spring-mass system the IL curve has a negative minimum.
[008] The insulation performance of an acoustic barrier is evaluated by the loss of sound transmission (TL). The ability of an acoustic barrier to reduce the intensity of noise being transmitted depends on the nature of the materials that make up the barrier. An important physical property of the TL sound control control of an acoustic barrier is the mass per unit area of its component layers. For best insulation performance, the heavy layer of a spring-mass system will often have a smooth, high-density surface to maximize reflection of noise waves, a non-porous structure, and certain material stiffness to minimize vibration.
[009] Typical classic putty layers are made of highly filled dense materials such as EPDM, EVA, PU, PP etc. These materials have a high density, typically above 1000 (kg/m3), a smooth surface to maximize reflection of noise waves, a non-porous structure and certain stiffness to minimize vibration. From this point of view, it is known that many textile fibers, either fine and/or porous in structure, are not ideal for noise insulation.
[010] Absorption is usually achieved by using porous layers. The absorption performance of an acoustic system is evaluated by the absorption coefficient (a dimensionless quantity). Absorbents are commonly made from open-pored materials, eg felt or foams.
[011] Both absorption and isolating systems by themselves have only a small frequency bandwidth where they work optimally. The absorber generally works best at high frequencies, while the insulator generally works best at low frequencies. Furthermore, both systems are less than ideal for use in a modern vehicle. The effectiveness of an insulator is strongly dependent on its weight, the higher the weight, the more effective the insulator. The effectiveness of an absorbent on the other hand is heavily dependent on the thickness of the material, the thicker the better. Both thickness and weight are, however, becoming highly restricted. For example, weight impacts vehicle fuel economy and material thickness impacts vehicle spatiality.
[012] For common spring-mass type insulators the absorption is very poor and close to zero, mainly because the surface of the mass layer is generally not porous. The spring mass system only shows a noticeable absorption peak in a narrow band around the resonant frequency. However, this is in the low frequency and not the area of interest for absorption, which is the mid- and high-frequency region.
[013] In the past, many attempts have been made to optimize sound isolation in a vehicle in order to reduce its mass (weight) while maintaining the same level of acoustic comfort. In vehicles treated with a traditional spring-mass system, the potential for such weight optimization is mainly represented by the heavy layer, and for this reason the optimization attempts made so far in such cases have focused on reducing the mass of a heavy layer. However, these attempts have shown that if the weight of the heavy layer is reduced beyond a certain physical limit, the insulation system no longer behaves like a spring-mass system and a loss of acoustic comfort inevitably occurs. In such cases, in recent years the use of additional absorbent material has been attempted to compensate for this loss of acoustic comfort.
[014] In the past, one way to deal with this problem was to use porous systems in their entirety. However, porous absorbents have very low sound insulation. For a porous system the IL curve increases with frequency in an approximately linear fashion, but only with a growth rate of around 6dB/Octave instead of the 12dB/Octave which can be observed when using an impenetrable barrier material such as a heavy layer.
[015] Another common practice to deal with the above mentioned problem was to place an absorbent material over a spring mass system. With such a configuration, it is expected that the presence of the additional material would primarily add absorbent properties to the sound attenuation system. At the same time it is also expected that, since this determines an increase in the total weight of the system, the same additional material would positively impact also the acoustic insulation of the underlying spring-mass system.
[016] Products of this type are often referred to as ABA (Absorbent-Barrier-Absorbent) systems. Most ABA systems are made with foam or felt as the first absorbent layer, a barrier, for example, in the form of a heavy layer material as discussed, and an absorbent layer which also functions as a spring layer for the spring mass system. This absorbent layer is also usually made of felt or foam. The barrier layer together with the absorbent layer directly in contact with the structure to which the system is applied should function as a spring mass system, while the absorbent top layer should function as an additional sound absorber.
[017] Based on experience, it is expected that when additional weight is placed on a spring-mass system, such additional weight should positively affect the insulation performance of the system; for example, an addition of 250 (g/m2) of material over a spring mass system with a heavy layer 2 (kg/m2) should result in a total IL increase of approximately 1 (dB), while an addition of 500 ( g/m2) of material over the same system should already result in an IL increase of 2 dB. An IL increase of more than 1 dB is normally considered relevant for the total noise attenuation in a vehicle's passenger compartment. For a heavy 1 (kg/m2) layer, already an addition of 150 (g/m2) of material should result in an effect of 1 (dB).
[018] It has been found that when an absorbent layer is added over a spring-mass system to obtain an ABA system with a heavy layer as a barrier, the increase in system IL that is observed is much smaller than what would be expected from added weight. In many cases, the addition of the absorbent layer leads to a reduction in system IL.
[019] In many ABA Systems applications a very soft felt (commonly designed as “wool”) with a weight per area between 400 and 600 g/m2 is used as an absorbent top layer. As such absorption is mechanically very soft (its Young's Modulus compression is very low, typically much less than that of standard air), it does not actively participate in the insulating function of the system, due to the bond between the fibers and the underlying heavy layer not is strong enough to provide a mass effect. As a result, the addition of the absorbent does not lead to any increase in the IL of the system and the insulating function of the system is determined only by the mass of the heavy layer that is placed over the decoupling layer. Very soft felt (or “wool”) materials are more expensive than common thermal moldable fibrous materials and are typically applied in the form of adhesives over the mass-spring system. Such application must be performed manually and this is an expensive operation.
[020] As an alternative, the ABA System can be obtained by molding or gluing a more traditional thermoformable felt with, for example, a weight per area between 500 and 2000 (g/m2) on the heavy layer, to act as an absorbent . It was found that in this case the application of the top of the absorbent layer has a negative effect on the insulation performance of the underlying spring-mass system, causing a deterioration of its IL curve. Such deterioration is caused by noise radiation from the system formed by the heavy layer and the absorbent top layer. In fact, a specific frequency exists, called the radiation frequency, at which vibrations are transmitted from the heavy layer to the top absorbent layer in a very efficient way, thus causing the top absorbent layer to propagate noise. At the radiation frequency, the top surface of the top absorbent layer vibrates even more than the underlying heavy layer. Due to this effect, the insertion loss of the ABA system is strongly compromised in the frequency range around the radiation frequency. In this frequency range, the IL of the ABA system is smaller than that of the spring-mass system from which it is obtained. In this sense, the addition of an acoustic function (absorption, through the absorbent added to the top) significantly deteriorates the original function of the system, that is, insulation; the acoustic irradiation of the system formed by the heavy layer and the porous top layer together deteriorates the insulation of the system, a case that has not been considered before in the prior art. Summary of the invention
[021] It is the aim of the present invention to obtain a sound attenuating trim piece, which works above the important frequency range for noise reduction in a vehicle, without the disadvantages of the prior art. In particular to optimize the use of weight to attenuate noise.
[022] The object of the invention is achieved by the sound attenuating trim piece according to claim 1, by comprising at least one insulating area with acoustic spring-mass characteristics comprising at least one mass layer and an adjacent decoupling layer to the dough layer and whereby the dough layer consists of a porous fibrous layer and a barrier layer, with the barrier layer being positioned between the porous fibrous layer and the decoupling layer and all layers are laminated together, and whereby the porous fibrous layer at least in the insulating area is adjusted to have a dynamic Young's modulus (Pa) of at least

[023] with AWb being weight per area (g/m2) of the barrier layer, AWp being weight per area (g/m2) of the porous fibrous layer, tp being the thickness (mm) of the porous fibrous layer and v (Hz) being the radiation frequency; whereby this radiation frequency v is at least 3000 (Hz), and whereby the barrier layer has a weight per area of at least 400 (g/m2).
[024] For the passenger compartment of a vehicle the frequency range between 800 (Hz) and 3000 (Hz) is the one where sound insulating trim pieces are the most effective. An ideal spring-mass system will show an IL curve with a growth rate of 12dB/Octave. Only the actual weight used in a layer of mass is decisive for the total insulation obtained. To obtain this same growth rate with an ABA System, the radiation frequency v must be above the upper frequency limit of the frequency range of interest, in this case at least above 3000 (Hz), preferably above 4000 (Hz ) or more preferably above 5000 (Hz) although this limit is application dependent.
[025] It was found that there is a relationship between the dynamic Young's modulus of the material constituting the porous fibrous layer and the radiation frequency. This relationship depends parametrically on the weight per area and thickness of the porous fibrous layer, and the weight per area of the barrier layer. To use a material for a porous fibrous layer such that the radiation frequency is high enough not to deteriorate the overall insulation performance of the underlying spring-mass system, preferably at least above 3000 (Hz), the dynamic Young's modulus E must be at least approximately

[026] This can be achieved, for example, by choosing the appropriate material, its weight per area, its thickness and the level of compression required. Not all material will reach the required Young's modulus.
[027] Adjusting the dynamic Young's modulus of the material constituting the porous fibrous layer so that it is above the minimum Young's modulus necessary for a radiation frequency to be outside the frequency range of interest, as claimed, the growth rate of 12dB/octave can be obtained from a system IL curve. In this sense, the IL curve of the ABA system according to the invention qualitatively behaves similarly to the IL curve of the underlying spring-mass system. At the same time, it is also observed that the IL curve of the ABA system according to the invention is higher than the IL curve of the underlying spring-mass system, the difference being due to the addition of weight of the porous fibrous layer. In this sense, the porous fibrous layer contributes to the insulating function of the system and the integral mass potential of the mass layer consisting of the barrier layer AND the porous fibrous layer can be used for the insulating properties of the trim piece. At the same time the porous fibrous layer with adjusted Young's modulus maintains absorbent properties.
[028] With the present invention, the absorbent top layer in the form of porous fibrous layer with Young's modulus according to the invention increases the amount of material that actively participates in the mass-spring effect.
[029] By using the ABA according to the invention it is now possible to adjust or adjust the trim piece for any particular vehicle application, in particular internal top or floor covering systems. The fit can be achieved in terms of performance, for example, better insulation at the same total weight, or weight, for example, less weight, at the same overall insulation performance.
[030] The resonant frequency of the spring-mass system as described in the introduction and the radiation frequency of the mass layer formed by the top porous fibrous layer and the barrier layer as described in the invention results in different and independent effects on the curve IL. Both appear on an IL curve of a multilayer according to the invention and have a negative effect on the insulation performance, both causing the presence of a drop in the IL curve. But, two dips are usually seen in two separate sections of an IL curve. For the considered multilayer types, the spring mass resonant frequency, also known as the resonant frequency, is normally observed in a range of 200 to 500 (Hz), while the mass layer radiation frequency, here disclosed as a frequency of radiation, is in a range above approximately 800 (Hz). For clarity we choose to use two different terms (frequency of “resonance” and “irradiation”) to distinguish between the two different frequencies.
[031] Although it is possible to make trim pieces that have an ABA-type configuration over their entire surface, it is also possible to have trim pieces with different areas dedicated to different acoustic functions (for example, exclusively absorption, exclusively insulation) or even areas combined.
[032] A preferred trim piece according to the invention is based on the idea that both absorption and isolation areas are necessary for fine regulation of sound attenuation in a car. By using the same porous fibrous layer over the entire area of the trim piece for both the insulating area and the absorption area, it is possible to integrate both functions in one trim piece, preferably in separate areas. People skilled in the art know from experience which areas need what kind of acoustic function, it is now possible to supply parts using this knowledge and at the same time using fewer materials within a part and are able to design the part according to the necessities. The trim piece according to the invention has at least one absorption area and an insulating area, however the natural number of areas by acoustic function (insulation or absorption) and/or the size of the areas may differ depending on the piece and location where the part is used and last and not least depending on current requirements.
[033] An absorption area is defined as an area of the trim piece that predominantly behaves as an absorbent.
[034] An insulating area is defined as an area on the trim part that behaves at least like a good insulator. Porous fibrous layer
[035] The use of porous fibrous materials, such as felts or non-woven fabrics, for the construction of acoustic absorbent pieces is known, in particular in the case of the top absorbent of an ABA System. The thicker the fibrous layer is, the better the sound absorption. However, the negative effect of the absorbent top layer on total insulation performance is not known in the art, in particular it is not known to regulate the characteristics of the porous fibrous layer to avoid this negative effect on insulation and fully exploit the mass of the porous fibrous layer for sound isolation purposes.
[036] It was found that the dynamic Young's modulus of the porous fibrous layer is related to the radiation frequency of the mass layer formed by the porous fibrous layer together with the barrier layer as follows:
[037] (Equation 1)

[038] with E being the dynamic Young's modulus (Pa) of the material constituting the porous fibrous layer, v being the radiation frequency (Hz), AWb being weight per area (kg/m2) of the impenetrable barrier layer, AWp being weight per area (kg/m2) of the porous fibrous layer and tp thickness (m) of the porous fibrous layer. According to this relationship an adequate value of the dynamic Young's modulus of the porous fibrous material allows the design of the trim piece with the radiation frequency outside the frequency range of interest and, therefore, an undisturbed insertion loss in a range of frequency of interest. In particular, if the dynamic Young's modulus of the porous fibrous layer is higher than the minimum value defined as

[039] with v0=3000Hz, then the radiation frequency of the spring mass system will appear above the frequency range of interest for application of the trim parts in vehicles, in particular in the passenger compartment.
[040] The frequency range of interest is insulation in a vehicle, especially when a certain weight from a spring-mass system is required, is in most cases up to 3000 (Hz), however, it can also be up to 4000 ( Hz) or even up to 5000 (Hz) depending on current application and required noise level. For example, when the insulation requirement is in the frequency range up to 3000 (Hz), v0 should equal 3000 (Hz) and, as a consequence, the dynamic Young's modulus should be at least
The. with AWb weight per area (g/m2) of the impenetrable mass layer, AWp weight per area (g/m2) of the porous fibrous layer and tp thickness (mm) of the porous fibrous layer. This results in a high dynamic Young's modulus in which the fibrous material can no longer be compressed easily.
[041] The trim piece according to the invention contains a decoupling layer, and a putty layer composed of
[042] a porous fibrous layer with at least one modulus of

[043] an impenetrable barrier layer with a weight per area AWb (g/m2) of at least 400 (g/m2).
[044] When all layers are laminated together to form one piece, then this trim piece will have an IL equivalent to that of an acoustic spring mass system with a growth rate of approximately 12dB/Octave and in accordance with the weight mass per combined area of the barrier layer and the porous fibrous layer.
[045] Furthermore, the porous fibrous layer adds the absorption function, which was the original reason for introducing ABA Systems and which is not available in the classic mass-spring system with a mass layer composed of impermeable materials only. Thanks to the adjustment of the Young's modulus of the porous fibrous layer, the radiation frequency of the porous fibrous layer together with the barrier layer will fall above the frequency range of interest and no longer disturb the overall insulation performance of the system.
[046] Compared to ABA Systems that are found in the prior art, the present invention differs in the fact that the top layer, or porous fibrous layer, added to the absorption function, actively participates in the insulating function of the system. This is possible only based on an appropriate choice of material characteristics and material design of the porous fibrous layer, as shown by equation (1) and as described in the examples.
[047] The porous fibrous layer can be any type of felt. It can be made from any thermoformable fibrous materials, including those derived from natural or synthetic fibers. Preferably the felt is made from recycled fibrous material such as lower quality cotton or other recycled fibers such as polyester.
[048] Usually a fibrous material is produced in raw agglomerate, that is, a semi-finished product in which the fibers are aggregated together. A cluster is within a reasonable homogeneous approximation. A raw agglomerate is composed of the sheet of material having an initial thickness and is characterized by its weight per area, due to the fibers being evenly distributed over the area. When a raw agglomerate is formed, for example, by compression, taking on a final shape. Finally, a layer with a certain thickness is obtained. The weight per area, that is, the weight of the material in the area unit, is maintained after the forming process. From the same white, varying final thicknesses can be obtained, depending on the level of compression.
[049] The dynamic Young's modulus of a fibrous material depends on varied parameters. First, the characteristics of the material itself, that is, the composition of the material, type and amount of fibers, type and amount of binders, etc. Also, for the same fiber recipe for the same fiber recipe, it depends on the material density, which is linked to the layer thickness. Therefore, for a certain felt composition, the dynamic Young's modulus can be measured at different thicknesses and will consequently assume different values, usually increasing when the thickness is decreased (for the same initial raw agglomerate).
[050] The fibrous felt material preferably comprises a bonding material, either as bonding fibers or in resin material, for example thermoplastic or thermosetting polymers. At least 30% Epoxy Resin or at least 25% bi-component bonding fibers is preferred. Other binding fibers or materials reaching the porous fibrous layer according to the invention are possible and not excluded. The porous fibrous layer material can be obtained through a needling process, or any other process that increases the dynamic compression stiffness of the material.
[051] Preferably the weight per area of the porous fibrous layer is between 500 and 2000 (g/m2), more preferably between 800 and 1600 (g/m2).
[052] An additional restriction is usually also the space available in the car where the acoustic trim piece can be placed. This restriction is normally given by the assembler and is in a maximum range of 20 to 25 (mm). All layers of the trim piece must divide this space. Therefore, the thickness of the porous fibrous layer is preferably between 1 and 10 (mm) and more preferably between 1 and 6 (mm). This leaves enough space for the decoupling layer. In particular, the decoupling layer can vary in thickness to follow the three-dimensional shape of the part which has to correspond with the available space on the car.
[053] In the prior art, highly compressed areas exist around the cavities in the trim part, which are necessary for transferring cables or assembly tools, these last areas are not normally dedicated to sound insulation as the acoustic fragility of the cavities compromises any insulating features in its vicinity. barrier layer
[054] The putty layer between the porous fibrous layer and the decoupling layer must be impenetrable (air-impermeable) to function as an ideal sound barrier. Only if the barrier layer is impenetrable air, the porous fibrous layer with the Young's modulus adjusted will work together with the barrier layer, as a mass layer for a mass-spring system. Although a heavy layer is given in the examples, alternative non-permeable mass barrier materials can be used.
[055] If the heavy layer is used as an impenetrable barrier layer, it preferably has a thickness between 0.2 and 5 (mm), more preferably between 0.8 and 3 (mm). The weight per area of the impenetrable mass layer is at least 0.4 (kg/m2), preferably between 0.5 and 2 (kg/m2). However, the choice of weight of the impenetrable barrier layer is linked to the design of the mass layer formed by the porous fibrous layer and the barrier layer together.
[056] The impenetrable barrier layer can be made of dense, highly filled materials which may include a thermosetting plastic including ethylene vinyl acetate (EVA) copolymer, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, elastomer thermoplastic/rubber, polyvinyl chloride (PVC) or any combination of the above.
[057] The choice of barrier material is dependent on the porous fibrous layer and the decoupling layer and should be able to form a laminate binding all layers together. Also materials that are sprayed or glued can be used. However, after bonding and/or formation of the trim piece, the mass barrier should be impervious to air in the final product.
[058] If necessary, an adherent layer in the form of a film, powder or liquid spray, as known in the art, can be used to laminate the barrier layer with the porous fibrous layer or with the release layer. Combined areas on the trim piece
[059] Typically, to reduce the sound pressure level in the passenger compartment, a vehicle requires a good balance of insulation and absorption provided by the acoustic trim parts. Different pieces can have different functions (eg insulation can be provided on the inside of the top, absorption can be provided on the carpet). There is a current trend, however, to achieve the finest subdivision of acoustic functions over single areas, in order to optimize overall acoustic performance. As an example, a top interior can be divided into two pieces, one providing high absorption and the other providing high insulation. Generally, the lower part of the interior of the top is more suitable for insulation, due to noise from the engine and the front wheels through this lower area is more relevant, while the upper part of the top is more suitable for absorption, due to some insulation. already fitted by other elements of the car, for example an instrumentation panel. In addition, the rear of the instrument panel will reflect sound waves coming through the top piece hidden behind the instrument panel itself. These reflected sound waves could be effectively eliminated using absorbent material. Similar considerations can apply to other acoustic parts of the car. For example, floor: insulation is predominantly of use in the foot product areas and tunnel area, while absorption is predominantly of use under the front seat and in the rear floor panels.
[060] The different local requirements can be covered by the sound insulating trim piece divided into areas with at least one area with predominantly sound absorption characteristics (absorption area), whereby the absorption area comprises at least one porous fibrous layer, and at least one other area with acoustic spring-mass characteristics (insulating area), whereby the insulating area consists of at least one mass layer and one decoupling layer. According to the invention the mass layer consists of a porous fibrous layer with the dynamic Young's modulus adjusted to have the radiation frequency outside the frequency of interest at least above 3000 (Hz) and a barrier layer with at least 400 (g/m2). For an absorption area the same porous fibrous layer can be used. Therefore, the porous fibrous layer is divided between the absorption area and the insulating area with a first portion in the insulating area being with a Young's Modulus adjusted so as to have the radiation frequency at least above 3000 (Hz) and a portion in the optimized absorption area for maximum absorption. In general, the thickness of the porous fibrous layer is higher in the absorption area than in the insulating area.
[061] The airflow resistance (AFR) of the porous fibrous layer in the absorption area is preferably between 300 and 3000 (Nsm-3), preferably between 400 and 1500 (Nsm-3). Higher AFR is better for absorption. However, it decreases with increasing thickness, therefore, the AFR is preferably between 400 and 1500 (Nsm-3) for a thickness of between 8 and 12 (mm).
[062] Adding additional absorption layers and/or tissue trusses can additionally increase absorption; either locally over the absorption areas or as an additional layer over basically the entire trim piece. The additional layers can be in the form of felt-like materials or the same as used for an additional porous fibrous layer and/or fabric lattice.
[063] Near the absorption areas and the insulating areas also intermediate areas will exist, which form the areas between an insulating area and an absorption area or around the edge of the part. These areas are less easy to identify as an absorption area or an insulating area mainly due to the process conditions creating a type of intermediate zones with a change in thickness, increasing in the direction of the absorption area and, therefore, behaving between a good absorbent and a insulating not too bad.
[064] Other types of intermediate areas may exist locally area following the three-dimensional piece shape that has to match the available space on the car. In the prior art, highly compressed areas exist around the cavities in the trim piece that are necessary for transferring cables or assembly tools. These last areas are not normally dedicated to sound insulation as the acoustic fragility of the cavities compromises any insulation characteristics in their vicinity. decoupling layer
[065] Like the decoupling layer, the standard material used for the spring layer in a classical mass-spring acoustic system can be used in the trim piece according to the invention following the same principles. The layer can be formed from any type of thermoplastic and thermosetting foam, closed or open, eg polyurethane foam. It can also be made from fibrous materials, for example thermal moldable fibrous materials, including those derived from natural and/or synthetic fibers. The decoupling layer preferably has a low compression stiffness of less than 100 (kPa). Preferably the release layer is also porous or open-pored to increase the spring effect. At first. the decoupling layer should be attached to the barrier layer over the entire surface of the part to have a more optimized effect, however, due to the very locally produced technique this may not be the case. As the part should function fully as a mass-spring acoustic system, small local areas where the layers that are not coupled will not detract from the total attenuation effect.
[066] The thickness of the decoupling layer can be optimized, however it is mostly dependent on the spatial constraints on the car. Preferably the thickness can be varied across the area of the part to follow the available space on the cart. Typically the thickness is between 1 and 100, in most areas between 5 and 20 (mm). additional layers
[067] An additional fabric truss can be placed over the porous fibrous layer to enhance sound absorption and/or to protect the underlying layers, eg from water etc. Additional absorbent material can be placed over the porous fibrous layer at least partially to further enhance the absorbent properties. The weight per area of the additional layer is preferably between 500 and 2000 (g/m2).
[068] The absorbent layer can be formed from any type of thermoplastic and thermosetting foam, for example, polyurethane foam. However for the purpose of noise absorption the foam must be open-pored and/or porous to enable the entry of sound waves in accordance with sound absorption principles as known in the art. The absorbent layer can also be made from fibrous materials, for example thermal moldable fibrous materials, including those derived from natural and/or synthetic fibers. It can be made of the same type of material as the fibrous porous layer, but preferably it should be noble to prevent interference with the insulation properties. The airflow resistance (AFR) of the absorbent layer is preferably at least 200 (Nsm-3), preferably between 500 and 2500 (Nsm-3). Absorption systems with more than one absorbent layer can also be placed over the porous fibrous layer.
[069] An additional fabric truss can also be placed either over the absorbent material or the porous fibrous layer to further elevate the sound absorption and/or to protect the underlying layers, eg against water etc. The fabric truss is a thin non-woven fabric with a thickness between 0.1 and around 1 (mm), preferably between 0.25 and 0.5 (mm). It preferably has an airflow resistance (AFR) of between 500 and 3000 (Nsm-3), more preferably between 1000 and 1500 (Nsm-3). By which the fabric lattice and underlying absorbent layer preferentially differ in AFR, to obtain increased absorption. Preferably the AFR of the tissue lattice differs from the AFR of the porous fibrous layer.
[070] The weight per area of the fabric truss can be between 50 and 250 (g/m2), preferably between 80 and 150 (g/m2).
[071] Fabric truss can be made from continuous or discontinuous fibers or blended fibers. Fibers can be made by meltblown or spunbond technologies. They can also be blended with natural fibers. Fabric trusses are, for example, made of polyester fibers, or polyolefins or the combination of fibers, for example, of polyester and cellulose, or polyamide and polyethylene, or polypropylene and polyethylene.
[072] These and other features of the invention will be clarified from the following description of preferred forms, given as non-restrictive examples with reference to the attached figures. Production Method
[073] The trim piece according to the invention can be produced with cold and/or hot molding methods commonly known in the art. For example, the porous fibrous layer with or without the barrier layer can be formed to obtain a material with the adjusted dynamic Young's modulus properties according to the invention and at the same time to form the part in the required dimensional shape and in a Step the decoupling layer can either be injection molded, or a layer of foam or fiber can be added to the back of the barrier layer. Definition of mechanical stiffness and compression measurement
[074] Mechanical stiffness is linked to the reaction that a material offers to an external stress excitation. Compressive stiffness is related to compression excitation and bending stiffness is related to bending excitation. Flexural stiffness is related to the bending moment applied to the resulting deflection. On the other hand, compressive or normal stiffness is related to the normal force applied to the resulting deformation. For a homogeneous plate made of an isotropic material, it is the product of the elastic modulus E of the material and the surface A of the plate.
[075] For a plate made with an isotropic material both compression and flexural stiffness are directly related to the Young's modulus of the material and it is possible to calculate one from the other. However, if the material is not isotropic, as is the case for most felts, the relationship explained does not apply, because bending stiffness is mainly linked to the material's Young's modulus in the plane, while compression stiffness is linked mainly to the Young's modulus out of plane. Therefore, it is no longer possible to calculate one from the other. Furthermore, both compression stiffness and bending stiffness can be measured under static or dynamic conditions and are different in principle under static and dynamic conditions.
[076] The irradiation of a layer of material is originated from vibrations of the layer orthogonal to its plane and is mainly linked to the material's dynamic compression stiffness. The dynamic Young's modulus of a porous material was measured with the commercially available “Elwis-S device” (Rieter Automotive AG) in which the sample is excited by the compression stress. Measurement using Elwis-S is described, for example, in BERTOLINI, et al. Transfer function based method to identify frequency dependent Young's modulus, Poisson's ratio and damping loss factor of poroelastic materials.(Symposium on acoustics of poroelastic materials) (SAPEM), Bradford, Dec. 2008.
[077] As these types of measurements are not yet generally used for porous materials, there are no official NEN or ISO standards. However, other similar measurement systems are known and used, based on similar physical principles, as described in detail in: LANGLOIS, et al. Polynomial relations for quasi-static mechanical characterization of isotropic poroelastic materials. J. Acoustical Soc. Am. 2001, vol.10, no.6, p.3032-3040.
[078] A direct correlation of Young's modulus measured with a static method and Young's modulus measured with a dynamic method is not direct and in most cases unimpressive, because the dynamic Young's modulus is measured in a frequency domain above of a predefined frequency range (eg 300-600 Hz) and the static Young's modulus value corresponds to the limit case of 0 (Hz), which is not directly obtainable from dynamic measurements.
[079] For the present invention the compression stiffness is important and not the static mechanical stiffness normally used in the prior art. Other measurements
[080] Airflow resistance was measured according to ISO9053.
[081] Weight per area and thickness were measured using standard methods known in the art.
[082] The transmission loss (TL) of a structure is and a measure of its sound isolation. It is defined as the rate, expressed in decibels, of the incident of acoustic power on the structure and the acoustic power transmitted by the structure to the receptive side. In the case of an automotive structure equipped with an acoustic part, transmission loss is not only due to the presence of the part, but also to the steel structure on which the part is mounted. Since it is important to assess the sound insulation capability of an acoustic automotive part independently from the steel frame on which it is mounted, insertion loss is introduced. The insertion loss (IL) of an acoustic piece mounted on a structure is defined as the difference between the transmission loss of the structure equipped with the acoustic piece and the transmission loss of the structure alone:

[083] The insertion loss and the absorption coefficient were simulated using SISAB, a numerical simulation software for calculating the acoustic performance of acoustic parts, based on the transfer matrix method. A transfer matrix method is a method for simulating sound propagation in layered media and is described, for example, in BROUARD B., et al. A general method for modeling sound propagation in layered media. Journal of Sound and Vibration. 1995, vol.193, no.1, p.129-142. Brief description of the figures
[084] Figure 1 Example of an internal top trim piece with sound isolation regions and sound absorption regions.
[085] Figure 2, 3, 4 and 5 Schematic sketches of the material of a trim piece according to the invention.
[086] Figure 6 Graph with insertion loss curves of samples A-D.
[087] Figure 7 Graph with absorption curves of samples A-D.
[088] Figure 8 Graph of dynamic Young's modulus in relation to weight per area and thickness of the porous fibrous layer. Examples
[089] Figure 1 shows an example of an internal top piece with two separate areas having different acoustic functions, in order to obtain an optimized compromise of insulation and absorption. Generally, the lower part of an inner bonnet piece is more suitable for insulation (I), because the noise pathways from the engine and front wheels through this lower area are more relevant, while the upper bonnet piece (II) is more suitable for absorption, due to some insulation is already provided by other elements of the car, for example, the instrumentation panel. Between these areas, in areas where the storage space is minimal or in areas with heavily three-dimensional shapes, it is not usually possible to identify the current acoustic characteristics, for example, due to both the damage of the decoupling layer or compression of a prime layer that it should function as an absorbent layer.
[090] To achieve better overall sound attenuation for an inner top trim piece the entire piece can be constructed with different distinctive areas:
[091] the insulating area (I) can be formed by combining the impenetrable barrier layer and a first portion of the porous fibrous layer with dynamically adjusted Young's modulus and the decoupling layer to form the alternative ABA System according to the invention with the total mass exploration of its upper layers working together as a single mass layer for the mass spring system, and the porous fibrous layer adding absorbent properties as well as preventing direct sound reflection, and
[092] the absorption area (II) can be formed by the portion of the porous fibrous layer not adjusted for insulation.
[093] Thus area I of the trim piece on the inner top shown contains the alternative ABA System according to the invention. Area II would contain the porous fibrous layer functioning as a standard absorbent known in the art.
[094] Figure 2 shows a schematic cross section of the trim piece according to the invention. With a layer of putty A consisting of the combination of the barrier layer 2 and the porous fibrous layer 1 according to the invention and with the spring layer B consisting of the decoupling layer 3. Together forming an acoustic ABA System. Sound-insulating characteristics can be expected from the combined mass barrier layer and the porous fibrous layer. Furthermore, the porous fibrous layer 1 will retain absorbent properties. Preferably an additional fabric lattice 5 can be placed over the porous fibrous layer 1 to elevate the sound-absorbing effect even further.
[095] Figure 3 shows the schematic cross section of a multilayer according to the invention. The multilayer according to the invention contains at least one area with sound insulating characteristics (I), later called insulating area, and an area with sound absorption characteristics (II), later called absorption area. The location of the areas on the part is dependent on the area of the vehicle where the part is used and the expected noise levels and frequency characteristics in this specific area. (See as an example of an internal worktop previously described.)
[096] The insulating area (I) and the absorption area (II) have at least the same porous fibrous layer (1), whereby the portion of the porous fibrous layer in the insulating area is compressed to form a rigid layer ( 1), such that the dynamic Young's modulus of the material constituting this porous fibrous layer is adjusted to have a radiation frequency above at least 3000 (Hz). The minimum value of the Young's modulus of the material constituting the porous fibrous layer necessary for such behavior is given by the formula
The. When this condition is fulfilled, the combined layer formed by the porous fibrous layer and the barrier layer will act as a rigid mass and will guarantee the optimal insulation performance according to the present invention.
[097] The insulating feature is formed with a layer of mass A consisting of the barrier layer 2 and the porous fibrous layer 1, according to the invention, and with the spring layer B consisting of the decoupling layer (3), together forming a mass-spring acoustic system. In Area I sound isolation characteristic can be expected as a consequence.
[098] In area II the porous fibrous layer 1 does not have the Young's modulus according to Equation 1, but allows sound absorption characteristics in this area. Preferably an additional fabric lattice (4) can be placed over the absorbent layer to elevate the sound-absorbing effect even further.
[099] Figure 4 shows an alternative multilayer according to the invention, based on the same principles as in Figure 3 (check for reference). The difference is that the area underneath the compaction is used for an addition of the barrier layer and the decoupling layer, producing yet another part. In practice the part will be more of a cross between figure 3 and 4, in particular the shape of automotive trim part is usually a 3D shape and this will influence the final layer overlay layout as well. Also between the insulating area and the absorption area there will be no clear boundaries, preferably intermediate areas.
[0100] Figure 5 shows an alternative layer overlay according to the invention where the barrier and decoupler are available over the entire surface of the part, including the absorption area. This can have advantages from a process standpoint, reducing the amount of production steps and/or manual labor involved using adhesives rather than full-coating layers throughout the part.
[0101] The insertion loss and sound absorption of different prior art multilayer noise attenuation constructions were measured or simulated using measured material parameters and compared with the insertion loss and sound absorption of a multilayer noise attenuation noise according to the invention. To have a direct comparison, for all samples the same foam decoupler with a density of 56 (kg/m3) and a thickness of 14 (mm) was used.
[0102] Comparative Sample A is a classic spring-mass system with the mass layer formed of a 3 (kg/m2) heavy layer EPDM material and injected foam as the decoupling layer. The total weight area of sample A was 3840 (g/m2).
[0103] Comparative Sample B is an ABA System according to the state of the art with the mass layer formed by a 3 (kg/m2) heavy layer EPDM material and injected foam as the decoupling layer. On top, an additional layer of cotton felt with 30% bicomponent binder fibers was used. The weight per area of the layer is 1000 (g/m2) and the thickness 9.8 (mm). Therefore, the total weight per area of the combination of the top felt layer and barrier layer would be 4 (kg/m2). The weight per total area of sample A was 4960 (g/m2).
[0104] Comparative sample C is also an ABA System according to the state of the art, with 400 (g/m2) of a noble wool with a thickness of 11 (mm) glued on the same spring mass system as used in the comparative samples above. The total area weight of the combination of top felt layer and barrier layer together is 3.4 (kg/m2).
[0105] Figure 6 shows the insertion loss (IL) curves of comparative samples A, B and C and sample D. The simulated insertion loss shown is the transmission loss of the system constituted by the multilayer and the steel plate on which is applied minus the transmission loss of the steel plate itself.
[0106] Figure 6 shows the IL curves of all prior art systems. Sample A is the classic spring mass system with a 12dB/Octave growth rate as expected and is used here as a reference. Sample B has a total weight for both top layers of 4 (kg/m2) and would be expected to show an insertion loss above reference sample A. However this is only true for the low frequency range below 630 ( Hz). Above 630 (Hz) the total insertion loss deteriorates in performance even below the expected insertion loss for a layer mass of 3 (kg/m2). The additional weight used for the top absorbent layer does not actually contribute to the overall insulating performance, it even negatively affects the insertion loss of the underlying spring mass system.
[0107] The dynamic Young's modulus of the felt of sample B at 10 (mm) was measured and is 108000 (Pa). According to equation (1), the heavy layer and the porous felt layer together will have a radiation frequency around 980 (Hz). In fact, a D1 dip is observed in Figure 6 for curve B. The D1 dip is on the curve between 800 and 1000 (Hz) for a calculation in one-third octave bands. The radiation frequency is in this case clearly within the frequency range of primary interest for attenuating noise in vehicles.
[0108] Also in comparative sample C it would be expected that the addition of the wool layer over the heavy layer would lead to some increase in the IL curve. However, the IL curve of Sample C is practically the same as that of the underlying spring-mass system (ie Sample A). Also for this sample the increase in weight does not lead to any increase in the observed sound insulation. In this case the top wool layer does not actually contribute to insulating performance.
[0109] Sample D is made according to the invention with a putty layer consisting of the porous fibrous layer of 1500 g/m2 over the barrier layer with a weight per area of 1500 (g/m2) and the decoupling layer, the Young's modulus of the porous fibrous layer being adjusted so that the radiation frequency of the barrier layer and the porous fibrous layer together is at least above 3000 (Hz). Insertion loss shows the same 12 dB/octave growth rate as well as the same level of insertion loss as sample A over at least a wide part of the frequency range of interest.
[0110] As the total weight of the mass layer for sample D is comparable with reference sample A - both being 3 (kg/m2) - it is here clearly shown that the full potential of the top absorbent layer can be used for performance of total isolation of the sample according to the invention.
[0111] The dynamic Young's modulus of the felt of sample D at 3.5 (mm) was measured and is 550000 (Pa). The minimum Young's modulus of the porous fibrous layer that is necessary to have a radiation frequency above 3000 (Hz) for sample D, according to the formula

[0112] is 390000 (Pa). Since the measured Young's modulus is greater than the minimum required Young's modulus, the porous fibrous layer together with the barrier layer will act as a mass in a spring-mass system in a frequency range of interest. According to equation (1), the heavy layer and the porous felt layer together will have a radiation frequency around 3600 (Hz). In fact, a D2 drop is observed in Figure 6 for the D curve. The D2 drop is on the curve between 3150 and 4000 (Hz) for a calculation in one-third octave bands. The dip appears at a frequency above 3000 (Hz) and is outside the frequency range of primary interest to attenuate noise in vehicles.
[0113] Figure 7 shows the absorption curves for the same comparative sample A and C as well as for sample D. The results show that a classical spring-mass layer -sample A - does not show any notable sound absorption. While loose wool, having a thickness of 11 (mm) shows good absorption. Sample D according to the invention, having a porous fibrous layer thickness of 3.5 (mm), still shows an average sound absorption. It is now known that to increase the total sound attenuation by 1 (dB) requires a smaller increase in weight for an isolation system and a considerable wide increase when an absorption system is chosen. Therefore, the overall increase in attenuation that can be achieved by utilizing the full weight potential of the materials used, more than makes up for less loss in absorption properties.
[0114] The design of a layer of putty according to the present invention therefore involves following the steps.
[0115] A felt composition and a weight per area are chosen.
[0116] A barrier layer and its weight per area are chosen.
[0117] The sum of these two area weights will provide the total mass of the spring mass system.
[0118] The two materials are then formed, in a way that each material takes the form of a layer and assumes a certain thickness.
[0119] The weight per area (AWp, g/m2) and the thickness (tp, mm) of the porous fibrous layer formed are measured. The weight per area (AWb, g/m2) of the formed barrier layer is measured.
[0120] Young's modulus of the porous fibrous layer is measured using Elwis-S, for a sample formed in thickness tp (Young's modulus measured: Emeas).
[0121] The minimum Young's Modulus (Emin) is required calculated by the formula

[0122] for AWp, AWb and tp the measured data from point 5 are taken. In this example the radiation frequency is taken to be at least above 3000 (Hz).
[0123] It must be verified that The condition E meas > Emin is fulfilled.
[0124] If the condition is fulfilled, the choice of material is satisfactory in accordance with the present invention and the fibrous material can be used in the determined thickness together with the chosen barrier layer, yours acting together as a putty layer in a spring mass system. Otherwise, the choice of parameters and in particular the choice of the Young's modulus of the felt must be modified and reiterated, starting from points 1 to 4, where the parameters (felt composition and/or weight per area of felt and/ or felt thickness and/or weight per mass barrier area) should be modified. Generally, choosing the weight per area of the barrier alone is not sufficient to produce an adequate layer of mass. If the condition is not fulfilled, in most cases the felt parameters must be properly chosen, in particular the dynamic Young's modulus.
[0125] In the sequence, the design processes described above are further explained with an example.
[0126] Figure 8 shows a plot of dynamic vs. Young's modulus. thickness for the insulating mass layer according to the invention. In this case a felt layer primarily of recycled cotton with 30% phenolic resin was taken. This material was used until not too long ago as a decoupler or absorbent layer, mainly in multilayer configurations. It is not chosen here as a restrictive sample, but rather as an example to show how to technically design the material according to the invention.
[0127] In Figure 8, L1000gsm line shows, as a function of layer thickness, the dynamic minimum Young's modulus that the porous fibrous layer with a weight per area of 1000 (g/m2) must have to comply with the invention. This was calculated with the formula

[0128] for a radiation frequency of 3000(Hz) and a weight per area for a heavy layer of 1500 (g/m2) and is then shown in Figure 8 as a straight line. Lines L1200gsm, L1400gsm and L1600gsm in the same figure show similar data for the area weights of the porous fibrous layer of 1200, 1400 and 1600 (g/m2). The dynamic Young's modulus of the porous fibrous layer of a given thickness and one of these area weights should be above the corresponding line for its area weight, to ensure that the radiation frequency is shifted at least 3000 (Hz) and thus outside the frequency range of primary interest for attenuating noise in vehicles.
[0129] In Figure 8, line A1000gsm shows, as a function of layer thickness, the measured Young's modulus of a primary cotton felt layer with 30% phenolic resin having a weight per area of 1000 (g/m2 ). On the same lines as in figure A1200gsm, A1600gsm shows similar data for the area weights of 1200 (g/m2) and 1600 (g/m2) respectively. For certain points the dynamic Young's modulus was measured and the behavior as described was extrapolated from these measurements. This material shows a rapid increase in dynamic Young's modulus already showing a radiation frequency above 3000 (Hz) at a weight per area of 1000 (g/m2) and a thickness of around 7.7 (mm). However, due to spatial restrictions, this thickness would not be preferable inside a car, for example, for an internal top.
[0130] In Figure 8, B1200gsm line shows, as a function of layer thickness, the dynamic Young's modulus of a layer of primary cotton felt material with 30% Epoxy resin and a weight per area of 1200 (g/m2 ). Line B1600gsm shows similar data for the case of weight per area of 1600 (g/m2). For certain points the dynamic Young's modulus was measured and the behavior as described below was extrapolated from these measurements. If one compares these data with those for phenolic resin felt discussed above, it is clearly visible that the bonding material has an effect on the material's compressive stiffness and consequently on the dynamic Young's modulus at a certain weight per area and thickness.
[0131] Line C1400gsm shows as a function of layer thickness the dynamic Young's modulus of a layer of primary cotton felt material bonded with 15% bicomponent bonding fibers and having a weight per area of 1400 (g/m2). For certain points the dynamic Young's modulus was measured and the behavior as described was extrapolated from these measurements.
[0132] In a set of samples, the influence of the binding material, in particular the type and amount of binder is seen in more detail. The. Figure 8 shows the influence of the binder material, in particular the type and amount of binder. Furthermore, Figure 8 explains how a porous fibrous layer is selected and adjusted in accordance with the invention.
[0133] For example, B1200gsm and L1200gsm curves are considered. The L1200gsm line is designed considering a barrier layer weight per area (AWb) of 1500 (g/m2). At a thickness of 8 (mm), the porous fibrous layer has a dynamic Young's modulus measuring 187000 (Pa), given by the curve B1200gsm. The lowest limit for the Young's modulus according to the invention, to have a radiation frequency above 3000 (Hz), is given by the line L1200gsm and is set at 757000 (Pa) to 8 (mm). Therefore, at 8 (mm) the layer of primary cotton felt material with 30% Epoxy resin and a weight per area of 1200 (g/m2) will have a radiation frequency of less than 3000 (Hz) and will not work according to the invention. In fact, according to equation (1), the material at 8 (mm) will have a radiation frequency at 1500 (Hz). At a thickness of 5.5 (mm), the porous fibrous layer has a measured dynamic Young's modulus of 730000 (Pa), given by the curve B1200gsm. The lowest limit for the Young's modulus according to the invention, to have a radiation frequency above 3000 (Hz), is given by the line L1200gsm and is defined at 520000 (Pa) to 5.5 (mm). Therefore, at 5.5 (mm) the layer of primary cotton felt material with 30% Epoxy resin and a weight per area of 1200 (g/m2) will have a radiation frequency above 3000 (Hz) and will work accordingly with the invention. In fact, according to equation (1) the material at 5.5 (mm) will have a radiation frequency at 3600 (Hz).
[0134] In summary, Figure 8 also shows how, once the weight per area of the barrier layer is fixed, to choose and adjust the characteristics of the porous fibrous layer (material type, weight per area, thickness) in order to have a Young's Modulus according to the invention.
[0135] When the porous fibrous layer is chosen and its Young's modulus is adjusted according to the invention, a surprising insulating effect is obtained, which is not strongly related to the AFR of the top layer. On the other hand, it has been found that the determining factor for obtaining a consistent insulation without any drop effect in a frequency range of interest, for example for automotive applications, is the Young's modulus of the top layer according to the invention.
[0136] When the thickness of the top layer is modified, both AFR and Young's modulus change and, in general, both AFR and Young's modulus are increased when the thickness of the layer is decreased. However, the heat of each of those parameters is related to the material's characteristics. AFR and Young's modulus, as well as other mechanical acoustic parameters of a porous material, are not just a function of thickness.
[0137] As an example, the AFR of two comparable felt materials of the same thickness is compared. An “air laid” felt commonly used for automotive application with a weight per area of 1000g/m2 shows an AFR of 3200 Nsm-3 at approximately 2.5mm. The same material at a thickness of 6mm shows an AFR of 1050 Nsm-3. In comparison a “needled” felt normally used for automotive applications, having approximately the same weight per area of 1000g/m2 shows an AFR 220 Nsm-3a approximately 6mm. At the same thickness, the two materials have different AFR. The two felts mainly differ in the way the fibers are processed to form a layer of material and this has an impact on the AFR.
[0138] The same consideration applies to the Young's modulus: for all materials, the Young's modulus is increasing when the thickness is decreased, however, two different materials of the same thickness do not necessarily have the same Young's modulus value and it can be characterized by many different Young's modules, depending mainly on its composition and the way they are produced.
[0139] Furthermore, the AFR and Young's modulus are independent parameters, the first being linked to the acoustic characteristics of the material and being linked to the mechanical characteristics of the material. As an example, two materials with the same AFR (bound, for example, to a similar fiber distribution in their materials) may have a different Young's modulus (bound, for example, to different amounts of binders in the material) and therefore , a different performance.
[0140] As can also be seen from the materials described certain materials are not suitable for forming the dough layer according to the invention, basically because they must be compressed to a no longer feasible thickness or at a cost of force. extremely high pressure, making the process no longer profitable. However, by adjusting the rate of binding material vs. fibrous material, the bonding material used, and the weight per area and/or thickness is possible to design materials suitable to be used as a fibrous porous mass layer according to the invention.
[0141] By adjusting the dynamic stiffness of the material constituting the top porous fibrous layer together with the weight per area of the barrier layer, according to the equation as disclosed, the radiation frequency of the mass layer formed by the combination of the porous fibrous layer and the barrier layer is displaced outside the primary range of interest for automotive applications and, at the same time, an additional mass effect thanks to the presence of the porous fibrous layer is obtained. The increase in total IL attachment loss depends on the weight per area of the porous fibrous layer together with the weight per area of the barrier layer and can be estimated with reasonable approximation.
[0142] The sound-insulating trim piece according to the invention whereby the barrier layer is between the porous fibrous layer and the decoupling layer and all layers are laminated together, can be used in a car, by example, as an internal soundboard as described above. However, it can also be used as a floor covering, possibly with a decorative layer or a carpet layer over it, whereby the carpet layer is preferably a porous system, for example a tufted carpet or a non-woven carpet. fabric. It can also be used on internal or external wheel linings. All applications can be in vehicles such as a car or a truck. Legend for figures I. Insulating area II. Combined insulation and absorption area A - putty layer comprising at least 1. a porous fibrous layer 2. a barrier layer B - Spring layer comprising at least: 3. a decoupling layer Additional layers: 4. absorption layer 5. Fabric truss layer

权利要求:
Claims (10)
[0001]
1. Sound attenuating trim piece, comprising at least one insulating area (I) with acoustic spring-mass characteristics comprising at least one mass layer (A) and a decoupling layer (3) adjacent to the mass layer, a dough layer consists of a porous fibrous layer (1) and a barrier layer (2), with the barrier layer being positioned between the porous fibrous layer and the decoupling layer and all layers are laminated together, characterized in that that the porous fibrous layer, at least in the insulating area, is adjusted to have a dynamic Young's modulus (Pa) of at least
[0002]
2. Sound attenuating trim piece according to claim 1, characterized in that it additionally comprises at least one absorption area (II) with sound absorption characteristics, wherein the absorption area comprises at least one portion of the same porous fibrous layer (1) and whereby the thickness of the portion of the porous fibrous layer in the absorption area is greater than the thickness of the portion of the porous fibrous layer in the insulating area (I).
[0003]
3. Sound attenuating trim piece, according to claim 1 or 2, characterized in that the weight per area AWp of the porous fibrous layer is between 400 and 2000 (g/m2).
[0004]
4. Sound insulating trim piece, according to any one of claims 1 to 3, characterized in that the thickness tp of the fibrous layer is between 1 and 10 (mm) in the insulating area.
[0005]
5. Sound attenuating trim piece according to any one of claims 1 to 4, characterized in that, at least partially, an additional absorption layer is placed over the porous fibrous layer.
[0006]
6. Sound attenuating trim piece according to claim 5, characterized in that, at least partially, at least the absorbent layer is covered with a layer of fabric lattice (4, 5).
[0007]
7. Sound attenuating trim piece, according to any one of claims 1 to 6, characterized in that the weight per area of the barrier layer is preferably between 500 and 2000 (g/m2).
[0008]
8. Sound attenuating trim piece according to any one of claims 1 to 7, characterized in that the porous fibrous layer (1) is at least partially covered with a layer of fabric lattice (4,5).
[0009]
9. Sound attenuating trim piece according to any one of claims 1 to 8, characterized in that a decorative layer or a carpet layer, preferably a tufted carpet or a non-woven carpet, is placed on top of the layer porous fibrous (1) and/or the additional absorption layers.
[0010]
10. Use of the sound-attenuating trim piece as an insulator or a combined and absorbent insulator, as defined in any one of claims 1 to 9, characterized in that it is like an automotive trim piece, such as an inner top, a cover floor or a wheel coating on a vehicle such as a car or truck.

类似技术:

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公开号 | 公开日 | 专利标题

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BR112013019385B1|2021-05-18|sound attenuating trim piece comprising at least one insulating area with acoustic mass-spring characteristics comprising at least one mass layer and an uncoupling layer adjacent to the mass layer and use of said sound attenuating trim piece

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BR112012018867A2|2020-09-01|trim part for sound insulation with acoustic mass-spring characteristics comprising a mass layer and a dissociation layer and use thereof

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US8261876B2|2012-09-11|Automotive trim part for sound insulation and absorption

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CA2788430C|2015-02-03|Automotive trim part for sound insulation and absorption

同族专利:

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公开号 | 公开日

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MY161803A|2017-05-15|

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MX2013010223A|2013-10-25|

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BR112013019385A2|2020-10-27|

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PL2684187T3|2015-10-30|

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RU2549214C1|2015-04-20|

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ES2543402T3|2015-08-19|

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CA2825378A1|2012-09-13|

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EP2684187A1|2014-01-15|

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JP2014515118A|2014-06-26|

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KR101624254B1|2016-05-25|

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ZA201306112B|2014-04-30|

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CN103534750B|2015-09-09|

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US8863897B2|2014-10-21|

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CN103534750A|2014-01-22|

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KR20140002734A|2014-01-08|

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US20140014438A1|2014-01-16|

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WO2012119654A1|2012-09-13|

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JP5791738B2|2015-10-07|

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EP2684187B1|2015-05-13|

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RU2013145078A|2015-04-20|

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AR085635A1|2013-10-16|

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法律状态:
2020-11-10| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2020-12-22| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2021-04-06| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-05-18| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 09/03/2011, OBSERVADAS AS CONDICOES LEGAIS. PATENTE CONCEDIDA CONFORME ADI 5.529/DF |

优先权:

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申请号 | 申请日 | 专利标题

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PCT/EP2011/053570|WO2012119654A1|2011-03-09|2011-03-09|Automotive noise attenuating trim part|

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