Automotive trim component for reducing tire noise and road vehicle equipped with it

Abstract

Road vehicle travelling on tires equipped with a trim component for reducing the noise radiated by said tires (10), wherein the trim (23-26) component comprises a sound-absorbing body with an external surface facing the tread of a tire (10) and positioned at least partially inside the front or the rear acoustic radiation horn of this same tire and wherein the sound-absorbing body has a maximum dimension of 800mm and an aspect ratio lower than 10.

Description

DescriptionAutomotive trim component for reducing tire noise and road vehicle equipped with itTechnical Field

[0001] The present invention relates to the field of automotive trim components placed on the exterior of a vehicle for reducing tire noise and a road vehicle comprising such automotive trim components.Background Art

[0002] In recent years, requirements for control and reduction of the noise radiated by road vehicles have become increasingly stringent. Essentially two factors determine this development. The first factor is the ongoing evolution in the legislation on exterior noise of road vehicles and the related progressive tightening of the permitted noise emission levels, as implemented, for example, in the Ell directive 540 / 2014. The second factor is a progressive increase in consumers' expectations, for what concerns in particular the acoustic comfort and the perceived quality a road vehicle may offer to them.

[0003] Tyres represent a major noise source contributing to the exterior and interior noise radiated by a road vehicle. This is true, in particular, for road vehicles fully powered by electric drives, for which tyres represent by far the most important source of noise.

[0004] Since more than 15 years now, in order to reduce the noise radiated by tyres, car manufacturers have installed cladding parts with sound absorbing properties in the region underneath the vehicles they produce. “With sound-absorbing properties" means that such parts may dissipate a substantial fraction of the acoustic energy carried by the acoustic waves that impinge on them and that are radiated, e.g. by the tires. Typical examples of such parts are sound absorbing underbody shields and sound absorbing wheelhouse outer liners.

[0005] A sound absorbing underbody shield generally consists of a substantially planar component connected to the underbody of a vehicle at a number of fixation points and obtained by compressing and consolidating under heata multilayer comprising one or more porous material layers. Thanks to the consolidation process, the component acquires the structural nature needed for its installation on the vehicle and for resisting aerodynamic loads, retaining at the same time a non-negligible level of sound absorption thanks to the porous material layers comprised in it. In order to increase its performance, further absorbers, typically installed on the side facing the vehicle body, may complement this kind of underbody shield. Traditional state of the art underbody shields of this kind are described, e.g., in US2020307470 or EP3137340.

[0006] Similarly, sound absorbing wheelhouse outer liners are substantially hemi- cylindrical parts fixed to the wheelhouse of a vehicle body and following its shape in such a way to surround the upper part of a tire. Similarly to the above-described underbody shields, they are generally obtained by compressing and consolidating under heat a multilayer comprising one or more layers comprising porous materials, and further absorbers installed on the body-facing side may complement them to increase their sound absorbing performance. State of the art wheelhouse outer liners are described, e.g. in EP3371363 and WO22189477.

[0007] State of the art solutions like the ones described here above pose a series of problems. First, these solutions may have a very complex shape, making their design complicated and very time consuming, and increasing their production cost. Furthermore, the complexity in shape may make their fixation to the vehicle body very critical -typically requiring several fixation points- and it may also lead to high production waste.

[0008] Second, the extension of these solutions may be very relevant, since they generally cover large surfaces of the vehicle body like the area under the floor or the wheelhouses. A sound absorbing underbody shield may have a surface in the order of about 2m2, and the same is true for a set of wheelhouse outer liners. Such large surfaces obviously lead to high material consumption and production cost.

[0009] Third, in spite of their extension and geometrical complexity, the performance of these solutions may be rather limited. The maximum reduction in exterior noise obtained thanks to these components andmeasured according to the standard ECE 51.03 (to which the Ell directive 540 / 2014 refers), is typically in the range of not more than 1dB(A). The reduction in interior noise obtained thanks to these components may be even smaller if not neglibile.

[0010] It is thus the purpose of the present invention to provide a solution to the above-listed problems of the state of the art. Thanks to the invention herein provided, it is possible to obtain a road vehicle with similar or even lower tire noise than road vehicles equipped with state of the art soundabsorbing cladding components, at the same time reducing material consumption and waste, improving ease of design and assembly, while reducing costs.Summary of invention

[0011] The object of the invention is achieved by a road vehicle comprising a trim component according to claim 1 , and a trim component according to claim 6.

[0012] In its main aspect, the invention concerns a vehicle travelling on road and comprising tires, each tire with a tread formed by its outer surface in regular contact with the road the vehicle is travelling on and forming with it a front and a rear acoustic radiation horn, the vehicle further comprising a trim component for reducing noise radiated by said tires, whereby the trim component comprises an inherently three-dimensional sound-absorbing body, which has a maximum dimension lower than 800mm and an aspect ratio lower than 10, and whereby at least part of the sound-absorbing body surface is opposite and facing the tread of a tire, and whereby said at least part of the sound-absorbing body surface is positioned at least partially inside either the front or the rear acoustic radiation horn of said tire.

[0013] According to a second aspect, the invention concerns an automotive trim component for use in a vehicle according to the main aspect of the invention. In particular, an automotive trim component for use in a vehicle for reducing the noise radiated by the tires of said vehicle, whereby the trim component comprises an inherently three-dimensional soundabsorbing body having dimensions lower than 800mm and an aspect ratio lower than 10, whereby at least part of the surface of the sound-absorbingbody is for facing the tread of a tire when mounted on a vehicle such that said at least part of the surface of the sound-absorbing body is at least partially positioned inside the front or the rear noise acoustic radiation horn of said tire.

[0014] An “inherently three-dimensional body” is any solid body which is not in the form of an open shell. An open shell is a body that may be obtained by plastically deforming a flat layer of material, e.g. by moulding it. An open shell may not be seen as “inherently three-dimensional”, since its overall geometry is obtained by plastically deforming a flat layer and may thus be described parametrically in a two dimensional way. The most trivial example of an open shell is obviously a plate or an arc of a cylinder. Other examples are the underbody shields and wheelhouse outer liners of the prior art, which are typically obtained by moulding one or more flat material layers. Therefore, they may not be considered "inherently three- dimensional” bodies in the sense of the invention herein disclosed.

[0015] A “sound-absorbing body” is a body purposefully designed for absorbing the sound radiated by a noise source such as a vehicle’s tires. Similarly, a “sound-absorbing material” is a material purposefully conceived for absorbing sound.

[0016] For a trim component intended to be installed on an associated road vehicle, “longitudinal”, "transverse” and “vertical” directions may be defined, which are identified with those of the associated road vehicle when the component is installed on it. In general, for a road vehicle the longitudinal direction is horizontal from front to back, the transverse direction is from left to right in the direction of travel and the vertical direction is from bottom to top. The dimension of a trim component in the longitudinal, transversal and vertical direction is meant to be its extension in the longitudinal, transversal and vertical direction respectively. In particular, the maximum dimension of a trim component is the maximum among its dimensions.

[0017] For a trim component with a given geometrical shape, the aspect ratio is the ratio of the maximum to the minimum of its dimensions.

[0018] To each tyre of a vehicle travelling on road, it is possible to associate two acoustic radiation horns, namely a front one and a rear one, each representing a geometrical volume in the vicinity of the tire-road contact patch as shown in Figure 1. Figure 1 shows a side view of a rotating tyre 10. Arrow 11 indicates the sense of rotation of the tyre, while arrow 12 shows the resulting direction of travel. Line 13 represents a hemi-circle centred at the centre point 14 of the contact patch between the tyre 10 and with a radius equal to the distance between this point 14 and the top of the tire. This radius is approximately equal to the diameter of the tire 10. Line 13, together with the road surface 15 and the tire tread surface 16, delimits two regions 17 and 18 one situated in front of the tire with regard to the travel direction and the other situated behind the tire with regard to the travel direction. Both regions must be intended as three-dimensional volumes, extending over the width of the tire tread surface in the transversal direction. Region 17, the one situated in front of the tire with regard to the direction of travel, is referred to herein as the front acoustic radiation horn of the tire. Similarly, region 18, the one situated behind the tire with regard to the direction of travel, is referred to herein as the rear acoustic radiation horn of the tire.

[0019]

[0020] Surprisingly, it was found that tire noise radiated by a road vehicle with the trim component according to the invention is comparable or even lower than that radiated by road vehicles equipped with state of the art solutions for reducing tire noise, such as sound absorbing underbody shields and wheelhouse outer liners. This is indeed very surprising, since the trim component according to the invention may be substantially smaller and lighter than typical sound absorbing underbody shields and wheelhouse outer absorbers.

[0021] This striking effect is obtained thanks to the shape and the design of the trim component according to the invention combined with its position when installed on the vehicle according to the invention. These features allow the trim component absorbing tire noise in a much more effective way compared to the above-mentioned prior art solutions. In fact, the trimcomponent according to the invention comprises a sound-absorbing body mounted on the road vehicle according to the invention in a position such that at least part of its surface is facing the tread of a tire and said part is located at least partially inside either the front or the rear acoustic radiation horn of said tire. In this way, said part of the surface of the soundabsorbing body may effectively intercept the sound energy of the acoustic waves radiated by the tire towards the front or towards the rear of the vehicle and convey it to the volume of the sound-absorbing body according to the invention, where it may be dissipated. Here and in what follows, for convenience reasons, the above-mentioned part of the surface of the sound-absorbing body is referred to as the “tread-facing surface” according to the invention. Furthermore, the entire volume of the soundabsorbing body according to the invention, with dimensions limited to 800 mm and aspect ratio limited to 10, is effectively involved in the sound absorption process. In contrast, in prior art solutions, due to their large surface area (necessary to conform to the shape of the vehicle panel they cover) and their positioning, only a small part of the material used in their production is actually involved in the sound absorption process.

[0022]

[0023] In the road vehicle with a trim component according to the invention, the trim component according to the invention is preferably installed onto or integrated into a longitudinal rocker and / or installed onto or integrated into a bumper. This allows positioning it in close proximity to a tyre, which -in turn- facilitates the positioning of the tread-facing surface at least partially inside the front or the rear acoustic radiation horn of a tire and enhances the noise reduction performance of the trim component according to the invention.

[0024] The fixation of the trim component according to the invention to the vehicle may be carried out using means for mounting known in the art, e.g. clips, screws, rails, etc., which may be comprised in the trim component according to the invention.The geometric extension and the aspect ratio of the trim component being limited, the number of fixation points needed may be substantially lower than those typically needed for sound-absorbing wheel-house outer liners and underbody shields of the prior art. In addition, the layout of the fixation points may be substantially simpler.

[0025] A further advantage of the limited number of fixation points and of the simplicity of their layout is that the trim component according to the invention may be much easier and cheaper to replace compared to state of the art sound-absorbing wheelhouse outer liners and underbody shields, e.g. when a certain wear limit is reached.

[0026] In the vehicle with the trim component according to the invention, the minimum distance between the tread-facing surface and the tire towards which it is facing is preferably between 20mm and 150mm, more preferably between 30mm and 100mm, even more preferably between 40mm and 70mm. The distance between the tread-facing surface and the tire towards which it is facing is intended to be measured with the vehicle stationary on a flat horizontal road. The closer the tread-facing surface to the tire towards which it is facing, the better the noise reduction performance of the trim component according to the invention. At the same time, for safety reasons a minimal distance between the tread-facing surface and said tire may have to be kept.

[0027] Furthermore, and always in order to enhance performance, in the vehicle with the trim component according to the invention, the trim component according to the invention is installed in such a way that the minimum distance between it and the road is as small as possible. In fact, the smaller this distance, the closer the sound-absorbing body according to the invention may be to the tire-road contact patch, which is known to be the area where most tire noise is radiated from. At the same time, for safety reasons it may be necessary to keep some clearance between the trim component according to the invention and the road. Preferably, in the vehicle according to the invention, the minimum distance between the trim component according to the invention and the road is between 20mm and 150mm, more preferably between 40mm and 100mm, even more preferably between 50mm and 80mm. The distance between the trim component according to the invention and the road is intended to be measured with the vehicle stationary on a flat horizontal road.

[0028] In a preferred embodiment, the trim component according to the invention is mounted onto the road vehicle according to the invention by means of a pivotable bracket, preferably oriented in the transversal direction and operated by an actuator. This embodiment is particularly advantageous in that, by operating on the actuator, it allows adjusting the orientation of the tread-facing surface as well as the distance between the trim component and the road, depending on the road conditions and on the vehicle speed. In particular, when the road vehicle is not travelling, e.g. it is parked, and / or when its speed is very low and exterior tire noise is of no concern, e.g. below 30km / h, the trim component according to the invention may be put in a completely retracted position, disappearing into the vehicle. Obviously, in order for this to be possible it may be necessary to create suitable recesses, e.g. in the underbody region of the vehicle, to accommodate the trim component. On the contrary, when the vehicle is travelling e.g. at high speed on a smooth road, the trim component according to the invention may be put in a “fully activated” position so to fully exploit its noise reduction potential.

[0029] Furthermore, in the trim component according to the invention, the soundabsorbing body according to the inventionis preferably at least partially encapsulated in a layer of rigid material, i.e. a material that is substantially more rigid than the materials comprised in the sound-absorbing body itself. This may be helpful for the installation of the trim component according to the invention on the vehicle according to the invention. It may also be useful in order to protect the sound-absorbing body from environmental agents and mechanical shocks, particularly those that may result from impacts against road projections, kerbs, pavements, etc. Preferably, the rigid material is a plastic material. Plastic is usually elastically deformable and can thus well absorb mechanical shocks. Furthermore, it may offer good wear-resistance and durability. In case the layer of rigid material is air-impermeable, in order for the trim component according to the invention to accomplish properly its function, this layer must not cover the tread-facing surface. However, in case the layer of rigid material is air-permeable, e.g., it is micro-perforated, a coverage of the tread-facing surface may be possible.

[0030]

[0031] The function of the tread-facing surface according to the invention is to effectively intercept the acoustic waves radiated by the tire it is facing either in the front or in the rear direction, allowing them to be absorbed by the sound-absorbing body according to the invention. In this respect, its positioning inside the front or the rear acoustic radiation horn of the tire, when the trim component is installed on the vehicle according to the invention and it is in use, is essential.

[0032] In principle, the tread-facing surface according to the invention may have any shape. In a first preferred embodiment, the tread-facing surface according to the invention has the shape of an arc of a cylinder arranged in transversal direction and approximately following the profile of the tire tread surface towards which it is facing at a certain distance from it. In this specific embodiment, the tread-facing surface according to the invention conforms to the shape of the tyre and of the wave-fronts of the acoustic waves radiated by it, which may enhance noise reduction performance.

[0033] A surface is considered “arranged in transversal direction” when the normal to the surface at any point has no or negligible component in the transversal direction. Such is a surface may be obtained by extrusion of a line in the transversal direction.

[0034] In a second preferred embodiment, the tread-facing surface according to the invention is flat, which favours ease of manufacturing. Preferably, in this embodiment, the tread-facing surface according to the invention is arranged in transversal direction and even more preferably its inclination is comprised between -60degrees and +60degrees. The inclination of a flat surface arranged in transversal direction is the angle formed by the longitudinal direction with the normal to the surface oriented in the outward direction with respect to the volume of the sound-absorbing body. Positive angles are measured in counter-clockwise direction.

[0035] Furthermore, in order to enhance the performance of the trim component according to the invention, the transversal dimension of the tread-facingsurface according to the invention is preferably at least 120mm, more preferably at least 180mm and even more preferably at least 220mm and the vertical dimension of the tread-facing surface according to the invention is preferably at least 100mm, more preferably at least 120mm and even more preferably at least 150mm.

[0036] Preferably, the extension of the tread-facing surface according to the invention in the transversal direction is larger than that of the tire tread surface towards which it is facing. In this way, the trim component according to the invention may better intercept and absorb the noise radiated by the tire.

[0037] Always in order to enhance the noise attenuating performance of the trim component according to the invention, preferably at least 50%, more preferably at least 75%, even more preferably at least 90% of the treadfacing surface according to the invention is inside either the front or the rear acoustic radiation horn of a tire of the vehicle according to the invention, when the trim component according to the invention is installed and in use. In this way, a substantial part of the tread-facing surface may be affected by the acoustic waves radiated by the tire either in the front or in the rear direction and may thus convey them to the sound-absorbing body, where they may be dissipated.

[0038]

[0039] The sound-absorbing body according to the invention consists of an inherently three-dimensional sound-absorbing body with dimensions lower than 800mm and an aspect ratio lower than 10. The combination of these features allows the whole volume of the body to be involved in the process of absorbing the acoustic energy carried by acoustic waves intercepted by the tread-facing surface. This is an advantage, compared to sound absorbing underbody shields and wheelhouse outer liners belonging to the state of the art where, due to their non-optimal positioning and two- dimensional nature, only a minor portion of the material used for their production is actually involved in the sound absorbing process, namely the portion that is the closest to the tire-road contact patch.

[0040] In order to further enhance its performance / volume ratio, the aspect ratio of the sound-absorbing body according to the invention is preferably lower than 8, even more preferably lower than 5 and its maximum dimension is preferably lower than 600mm, even more preferably lower than 400mm. The maximum dimension is preferably the longitudinal dimension.

[0041]

[0042] No particular restriction applies to the shape of the trim component according to the invention. In a first preferred embodiment, the trim component according to the invention has the shape of a wedge, wherein the base of the wedge comprises the tread-facing surface according to the invention.

[0043] In a second preferred embodiment, the trim component according to the invention has the shape of a half-cylinder, wherein one of the hemi-circles constituting the bases of the half-cylinder comprises the tread-facing surface according to the invention.

[0044] In a third preferred embodiment, the trim component according to the invention has the shape of a half-cone or a half-truncated-cone, wherein the hemi-circle constituting the base of the half-cone or half-truncated cone comprises the tread-facing surface according to the invention.

[0045] In a further preferred embodiment, the trim component according to the invention has the shape of a tapered polyhedron, such as a pyramid or a truncated pyramid. Also in this preferred embodiment, the base of the tapered polyhedron comprises the tread-facing surface according to the invention.

[0046] In all the above-listed preferred embodiments, the tread-facing surface is preferably either in the form of an arc of a cylinder following the profile of the tire it is facing at a distance from it or in the form of a flat surface oriented in transversal direction, with an inclination preferably between +60degrees and -60degrees.

[0047] The above-mentioned preferred shapes for the trim component according to the invention are particularly advantageous in that they may enhance the ratio between the area of the tread-facing surface and the volume ofthe trim component according to the invention and then the corresponding performance / volume ratio.

[0048] Furthermore, and very advantageously, by means of a trim component according to the invention with these shapes it may also be possible to improve the aerodynamic performance of the vehicle according to the invention. For example, when a wedge-shaped trim component according to the invention is installed onto or integrated into the front bumper of the road vehicle according to the invention, the trim component according to the invention may act as an air-guide, making the air-flow around the front tire smoother and less turbulent. In this way, reduction of tire noise may be combined with an improvement of the aerodynamic performance of the vehicle according to the invention.

[0049] In addition to this, when the trim component according to the invention is installed on a pivotable bracket, e.g. oriented in transversal direction, and operated by an actuator as previously described, the noise-reduction function and the aerodynamic-improvement function of the trim component according to the invention may be combined and adjusted simultaneously, depending on circumstances such as speed and road conditions.

[0050] The trim component according to the invention is preferably separate, that is, it is a trim component installed on the vehicle according to the invention independently and separately from other trim components. However, the trim component according to the invention may also be connected to and / or integrated with other trim components such as an underbody shield and / or a wheelhouse outer absorber.

[0051]

[0052] In order to accomplish its function, the sound-absorbing body according to the invention may comprise any kind of material known in the field as suitable for absorbing sound, in particular porous fibrous materials and / or open cell foams, in particular polyurethane foams, and / or air-permeable polymeric films, in particular micro-perforated films, and / or air-permeable thin non-wovens, known in the field as “scrims”. In certain embodiments, the sound-absorbing body according to the invention may even comprise materials that are not suitable for absorbing sound as such, but maycontribute to sound-absorption when combined with other materials. Examples are air-impervious polymeric films, air-impervious scrims and heavy barrier layers made with polymeric and / or rubbery materials.

[0053] In principle, no restriction applies to the arrangement of materials in the sound-absorbing body according to the invention.

[0054] In a first embodiment, the sound-absorbing body according to the invention is a body, consisting of a first porous fibrous material. This layout may be advantageous for its simplicity, which may lead to ease of manufacturing and low cost, as well as for its environmental sustainability.

[0055] The first porous fibrous material may comprise any kind of natural and / or synthetic fibers common in the industry. Examples of natural fibers are cotton, wool, flax, hemp, bamboo, sisal, jute, and abaca fibers. Examples of synthetic fibers are polypropylene fibers, polyethylene fibers, polyester fibers, for instance polyethylene-terephthalate (PET) fibers, polylactic acid (PLA) fibers and polyamide (PA) fibers, in particular polyamide 6 or polyamide 6.6 fibers. Synthetic fibers may be mono-component or bicomponent fibers. Mono-component fibers are made from a single material, while bicomponent fibers are synthetic fibers made from two polymers of different chemical and / or physical structure that are tightly connected to each other along the fiber length. Bicomponent fibers may be produced using processes known in the art, e.g. by melt spinning.

[0056] The first porous fibrous material may consist of only one single kind of fibers but it may also be a homogeneous mix of fibers of different kinds.

[0057] In this first embodiment, the density of the first porous fibrous material is preferably between 20kg / m3and 100kg / m3, more preferably between 50kg / m3and 80kg / m3. A lower density of the first porous fibrous material may make the sound-absorbing body according to the invention lighter and more porous, favouring the involvement of the entire volume of the sound-absorbing body in the sound absorption process.

[0058] The Air Flow Resistivity (AFR) of the first porous fibrous material is preferably between 10000Ns / m4and 50000Ns / m4, more preferably between 10000Ns / m4and 30000Ns / m4. A not-too-high AFR may be preferred in order to allow that the entire volume of the body is effectivelyinvolved in the sound-absorption process. Here and in what follows, AFR values are intended as measured according to ISO 9053-1 :2018.

[0059] The fibers of the first porous fibrous material are preferably staple fibers, with a length comprised between 32mm and 76mm. Staple fibers are fibers that, differently from endless filaments, come in discrete predefined lengths. Furthermore, in order to enhance sound absorption performance, the fineness of the fibers is preferably between 0.5denier and 8denier, more preferably between 0.5denier and 5denier, even more preferably between 0.5denier and 2denier. For a given mass of porous fibrous material, finer fibers provide a better sound-absorption performance.

[0060] Advantageously, the fibers of the first porous fibrous material may be at least partially of a recycled nature, in order to reduce the environmental impact of the manufacturing process of the sound absorbing body according to the invention, for what concerns specifically material consumption. In particular, the first porous fibrous material may be in the form of a shoddy natural fiber, for example a shoddy cotton, or in the form of a shoddy synthetic fiber, for example a shoddy polyester. A shoddy type of material is here defined as comprising at least 51 % by weight of recycled fibers the concerned material. So for instance, a shoddy cotton contains at least 51 % by weight of recycled cotton fibers, being the remaining 49% by weight constituted by fibers of a different material and / or by virgin fibers.

[0061] Furthermore, the first porous fibrous material preferably comprises a binder, preferably in an amount comprised between 10% and 50% by weight. A binder may improve the mechanical consistence of the soundabsorbing body according to the invention so that it can be easily handled during the production process and / or the installation process on the vehicle according to the invention. The binder may be of a thermoset or of a thermoplastic nature. In both cases, some kind of thermal treatment is needed in order to activate it. A thermoset binder is preferably in the form of an epoxy resin or a phenolic resin or a mixture of both. A thermoplastic binder is preferably in the form of thermoplastic binder fibers. These are fibers comprising at least one portion which melts as a result of a thermaltreatment, forming droplets that bind all the other fibers at their crossing / contact points. The melting temperature of the binder fibers (or the portion of the binder fibers that melts) must obviously be lower than that of all the other fibers (and of the portion of the binder fibers that possibly does not melt). Binder fibers may be mono-component or bicomponent fibers. A thermoset binder is preferable when enhanced mechanical properties and structural consistence are needed. On the other hand, a binder in the form of thermoplastic binder fibers is preferable when very complex 3-dimensional shapes have to be realized.

[0062] In a preferred execution of this first embodiment, the first porous fibrous material comprises bicomponent side-by-side crimped fibers, preferably in an amount comprised between 10% and 70% by weight, and a binder.

[0063] Bicomponent side-by-side crimped fibers are bicomponent fibers formed by spinning the two fiber polymers together simultaneously and side by side so that both polymers are in contact with the external surface of the resulting fiber, whereby the two polymers differ in some physical property such that the fiber takes a curved or crimped shape during the spinning process. For example, a difference in thermal shrinkage properties between the two polymers may determine such a fiber curvature. Thanks to their bulkiness, bicomponent side-by-side crimped fibers allow a particularly effective filling of the volume of the sound-absorbing body according to the invention, resulting in a lower weight. Furthermore, they offer also superior formability properties, leading to greater ease and flexibility of design. Preferably, the bicomponent side-by-side crimped fibres have an overall round cross-section, more preferably with a hollow core, in which case they are known as hollow conjugated fibers. However, other cross-sections can be used as well. In the bicomponent side-by-side crimped fibers the first polymer is preferably polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) and the second polymer is a copolymer of polyethylene terephthalate (coPET) or a copolymer of polybutylene terephthalate (coPBT).

[0064] In this preferred execution of the first embodiment, the first porous fibrous material further comprises a binder, preferably in an amount comprisedbetween 10% and 50% by weight. The binder may be a thermoset binder, preferably in the form of an epoxy or a phenolic resin, or a thermoplastic binder, preferably in the form of thermoplastic binder fibers and even more preferably in the form of thermoplastic bicomponent core-sheath binder fibers. Bicomponent core-sheath binder fibers are bicomponent fibers wherein one of the two components (the sheath) surrounds the other (the core). The sheath component is the part of the fiber that melts during thermal treatment as described above. Also in the bicomponent coresheath binder fibers the first polymer is preferably polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) and the second polymer is a copolymer of polyethylene terephthalate (coPET) or a copolymer of polybutylene terephthalate (coPBT).

[0065] In this preferred execution of the first embodiment, particularly preferred is the case in which the first porous fibrous material entirely consists of polyester fibers. An example may be a mix of bicomponent PET / CoPET side-by-side crimped fibers in an amount of 10% to 70% by weight, bicomponent PET / CoPET core-sheath binder fibers in an amount of 10% to 50% by weight and mono-component PET fibers in an amount of 10% to 70% by weight, wherein the percentages corresponding to the different fiber types add up to 100%. A sound-absorbing body entirely made of polyester allows easier recycling of either production cut-offs and / or of the sound-absorbing body as a whole at the end of the product lifecycle.

[0066] When polyester is used for the fibers constituting the first porous fibrous material, at least a part of it may advantageously be of a recycled nature. For example, the PET may be obtained from consumer products like PET bottle flakes or from PET packaging items or from PET marine products like fishing nets, by melting them and forming them into pellets that may be used for the spinning process. Using recycled polyester has the advantage of reducing the environmental impact of the manufacturing process of the trim component according to the invention, in particular its CO2 footprint. Preferably at least 20% by weight, more preferably at least 50% by weight and even more preferably at least 70% by weight of the polyester used forthe polyester fibers comprised in the sound-absorbing body according to the invention is recycled polyester.

[0067]

[0068] In a second embodiment, the sound-absorbing body according to the invention comprises a body consisting of the first porous fibrous material, at least partially coated with a layer consisting of a second porous fibrous material. In this embodiment, preferably at least the tread-facing surface is coated with said layer of a second porous fibrous material. The second porous fibrous material may coincide with the first porous fibrous material. However, it is preferably different from it and, thanks to this differentiation, it provides an enhancement both of the sound-absorption properties and of the mechanical consistence of the sound-absorption body according to the invention.

[0069] In this second embodiment, the second porous fibrous material has preferably a much higher bending modulus than the first porous fibrous material. In this second embodiment, the second porous fibrous material has a bending modulus of at least 70 MPa, preferably between 70 MPa and 1300 MPa, preferably between 100 MPa and 950MPa, preferably between 150 MPa and 700MPa, measured according to ISO 178:2019 at 23 degrees Celsius and 50% relative humidity. This in order to enhance the structural properties of the sound-absorbing body according to the invention and thus favour its handling during the manufacturing and installation processes. Preferably, the coverage of the layer consisting of the second porous fibrous material is sufficient to confer to the soundabsorbing body according to the invention a self-supporting character. “Self-supporting character” means that the sound-absorbing body according to the invention does not substantially deform under the load of its own weight, independently from its orientation in space. In a particularly preferred embodiment, the layer consisting of the second porous fibrous material completely covers the body consisting of the first porous fibrous material.

[0070] Furthermore, the second porous fibrous material preferably has an AFR substantially higher than that of the first porous fibrous material. Thisrealizes an impedance mismatch at the interface between the two materials, which may help enhancing the sound-absorption properties of the sound-absorbing body according to the invention in specified frequency ranges, in particular between 800Hz and 1600Hz, where the exterior noise radiated by tyres is particularly pronounced. In this second embodiment, the second porous fibrous material has an AFR preferably between 35000Ns / m4and 1200000Ns / m4and even more preferably between 60000Ns / m4and 900000Ns / m4.

[0071] In this second embodiment, the layer of the second porous fibrous material is preferably substantially thinner than the dimensions of the sound absorbing-body according to the invention. Preferably, the thickness of the layer of the second porous fibrous material is comprised between 2mm and 10mm, more preferably between 3mm and 6mm. The area weight of the layer of the second porous fibrous material is preferably comprised between 600g / m2and 1600g / m2, more preferably between 800g / m2and 1400g / m2.

[0072] The second porous fibrous material may comprise any kind of natural and / or synthetic fibers common in the industry, similarly to the first porous fibrous material. In particular, all the types of fibers and fiber mixes described in relation to the first porous fibrous material may be used also for the second porous fibrous material, including the fibers and the fiber mixes described for the preferred executions of the first embodiment of the sound-absorbing body according to the invention. However, the second porous fibrous material has preferably a density higher than that of the first porous fibrous material. This means that even when the same fibers or fiber mix is used for the first and second porous fibrous material, these are preferably more compressed in the second porous fibrous material than in the first porous fibrous material. Preferably, the density of the second porous fibrous material is between lOOkg / m3and 600kg / m3, more preferably between 200kg / m3and 450kg / m3.

[0073] In a particularly preferred execution of the second embodiment, the layer of the second porous fibrous material consists of thermoplastic bicomponent binder filaments, preferably with a core-sheath section.Filaments, sometimes referred to also as “continuous filaments” or “endless filaments”, are continuous fibres with indefinite length, i.e. not cut to a specific length like staple fibers. This confers to the layer surprisingly good mechanical properties, deriving from the synergy between the endless nature and the bicomponent nature of the filaments. On one hand, endless filaments span the whole surface of the layer. On the other hand, the melting of the sheath polymer guarantees the formation of bonding points between the cores of the endless filaments, bonding points that are uniformly distributed along the whole length of the filaments themselves. The result is a network of endless filaments spanning the whole surface of the layer and strongly linked to each other. Such a network has excellent mechanical properties, in particular in terms of bending stiffness.

[0074]

[0075] A third embodiment of the sound-absorbing body according to the invention may be derived from the previous one by inserting between the body consisting of the first porous fibrous material and the layer consisting of the second porous fibrous material an air-permeable film. The presence of the air-permeable film may further help adjust and enhance the soundabsorption performance of the sound-absorbing body according to the invention in specific frequency ranges, in particular between 800Hz and 1600Hz. In this third embodiment, the Air Flow Resistance of the air- permeable film is preferably higher than that of the layer consisting of the second porous fibrous material, more preferably at least 20% higher than that of the layer consisting of the second porous fibrous material. For a layer of given material, the Air Flow Resistance is the product of the Air Flow Resistivity and the thickness.

[0076] In this third embodiment, the thickness of the air-permeable film is preferably between 50 micrometres and 800 micrometres, more preferably between 100 micrometres and 500 micrometres. Its area weight is preferably between 50g / m2and 800g / m2, more preferably between 100g / m2and 500g / m2. Preferably the air-permeable film is of a polymeric nature and it preferably comprises at least one of the polymers or copolymers selected from the group consisting of polyester such aspolyethylene terephthalate (PET) or polybutylene terephthalate (PBT); polyamide such as polyamide 6 or polyamide 66; polyolefin such as polypropylene (PP), polyethylene (PE); thermoplastic elastomers (TPEs) such as thermoplastic polyolefin (TPO), thermoplastic polyurethane (TPU); elastomers such as EPDM-based elastomers or butadiene-based elastomers or silicones; high performance polymers such as polytetrafluoroethylene (PTFE), polyetherimide, polysulfone, polyethersulfone, polyetheretherketone (PEEK); ethylene vinyl acetate (EVA); biopolymers such as polylactic acid (PLA). Preferably the material or materials for the air-permeable film and the material or materials of the first and / or second porous fibrous material belong to the same chemical group, making recycling easier. Furthermore, the film may be mono-layer, bi-layer or multi-layer. In order to favour processability, the air-permeable film has preferably a tensile strength at break higher than 20 MPa and a strain at break higher than 100%. In case the film is anisotropic, these values refer both to machine-direction and cross-direction. Stress and strain at break are measured according to the current version of ISO 527- 1 :2019 and 527-3:2018.

[0077] In a variant of this third embodiment, the air-permeable film may be replaced with an air-impermeable film, which may increase the mechanical robustness of the sound-absorbing body according to the invention. In this variant, the thickness of the air-impermeable film is preferably between 50 micrometres and 800 micrometres, more preferably between 100 micrometres and 500 micrometres. Its area weight is preferably between 50g / m2and 800g / m2, more preferably between 100g / m2and 500g / m2. Being the film very thin and light, its air-impermeability does not compromise the sound-absorption properties of the sound-absorbing body according to the invention.

[0078] In another variant of this third embodiment, the air-permeable film may be replaced by a thin air-permeable non-woven, known in the field as "scrim". Similarly to the case of the air-permeable film, the Air Flow Resistance of the scrim is preferably higher than that of the layer consisting of the second porous fibrous material, more preferably at least 20% higher thanthat of the layer consisting of the second porous fibrous material. The area weight of the scrim is preferably not higher than 400 g / m2, more preferably not higher than 200 g / m2, in order not to substantially increase the overall weight of the sound-absorbing body according to the invention. Preferably, in this variant of the third embodiment the material or materials used for the scrim and the material or materials used for the first and / or second porous fibrous material belong to the same chemical group (e.g. they all consist of polyester), making recycling easier.

[0079]

[0080] In a fourth embodiment, the sound-absorbing body according to the invention consists in a closed hollow shell made with a layer of the second porous fibrous material. This fourth embodiment may be seen as a variant of the second embodiment, wherein the layer consisting of the second porous fibrous material is a closed shell and the body consisting of the first porous fibrous material is replaced by an air-cavity inside said shell. This embodiment is particularly advantageous for its lightness and simplicity of design.

[0081]

[0082] In a fifth embodiment, the sound-absorbing body according to the invention comprises a body consisting of the first porous fibrous material, at least partially directly coated with an air-permeable foil or with a scrim, wherein the air-permeable foil or the scrim have the same features described in relation to the third embodiment and its variant. In this embodiment, the tread-facing surface is preferably coated with said air- permeable foil or scrim. This fourth embodiment may be seen as a variant of the second embodiment, wherein an air-permeable foil or a scrim replaces the layer consisting of the second porous fibrous material. This may make the sound absorbing body according to the invention lighter and cheaper. Furthermore, coating the external surface of the sound-absorbing body according to the invention with an air-permeable foil or a scrim may make it more robust against environmental agents and stone chipping.

[0083] In a variant of this fifth embodiment, the air-permeable film may be replaced with an air-impermeable film, in order to enhance the abovementioned robustness against environmental agents and stone chipping. In this variant, the thickness of the air-impermeable film is preferably between 50 micrometres and 800 micrometres, more preferably between 100 micrometres and 500 micrometres. Its area weight is preferably between 50g / m2and 800g / m2, more preferably between 100g / m2and 500g / m2. Being the film very thin and light, its air-impermeability does not compromise the sound-absorption properties of the sound-absorbing body according to the invention.

[0084] The above-listed embodiments of the sound-absorbing body according to the invention represent exemplary embodiments in which the soundabsorbing function is realized primarily thanks to porous fibrous materials. However, it is possible to obtain alternative embodiments of the soundabsorbing body according to the invention by replacing in the abovedescribed five embodiments the first and / or the second porous fibrous material with an open cell foam, having similar features in terms of geometry and, when applicable, AFR. However, open cell foams are typically lighter than porous fibrous materials. Thus, embodiments comprising open-cell foams may be advantageous in making the soundabsorbing body according to the invention lighter. Preferably, the open-cell foam or foams used in the sound-absorbing body according to the invention have a density between 10kg / m3and 50kg / m3, more preferably between 10kg / m3and 35kg / m3. Furthermore, the open-cell foam or foams is preferably a polyurethane foam.

[0085] The embodiments described here above for the sound-absorbing body according to the invention represent just possible material arrangements to obtain this same sound-absorbing body. By considering the features of the materials here above described, in particular their nature, density, thickness, area weight and AFR, the person skilled in the art may easily derive from these embodiments further material arrangements that may be suitable depending on the circumstances.

[0086]

[0087] In addition to this, further embodiments of the trim component according to the invention may be derived from the description also by combining thedifferent embodiments and examples of the invention and may be also derived from the description of the embodiments shown in the figures. The figures are schematic and not necessarily in scale.

[0088] Brief description of drawings

[0089] Figure 1 shows an automotive tire and shows how to define the front and the rear acoustic radiation horn of a tire. The content of Figure 1 has already been described and commented on in detail above.

[0090] Figure 2 shows a side view of a road vehicle according to the invention.

[0091] Figures 3 and 4 show a side view of the rear part of a road vehicle according to the invention, in particular the area around the rear tyre.

[0092] Figures 5a to 5c shows examples of the trim component according to the invention with different shapes.

[0093] Figures 6a to 6e show material arrangements for the sound-absorbing body according to the invention, corresponding to the previously described five embodiments.

[0094] Figure 7 shows the test set-up for the measurement of Exterior Acoustic Transfer Functions.

[0095] Figure 8 shows the sound source positions in correspondence of the rear tire used for the measurement of the Exterior Acoustic Transfer Functions as well as for the measurement of the Interior Acoustic Transfer Functions.

[0096] Figure 9 shows the comparison between the Exterior Acoustic Transfer Functions obtained for a test vehicle with different trim configurations.

[0097] Figure 10 shows the comparison between the Interior Acoustic Transfer Functions obtained for a test vehicle with different trim configurations.

[0098]

[0099] Figure 2 shows a side view of a vehicle 20 according to the invention, equipped with front tire 21 and rear tire 22. The vehicle comprises trim components 23, 24, 25 and 26 according to the invention. Trim components 23 and 26 are installed onto the vehicle front bumper 27 and onto the vehicle rear bumper 28 respectively. Trim components 24 and 25 are installed onto the longitudinal rocker (often referred to also as "side sill") 29. Trim components 23 and 24 are for reducing the noise radiatedby the front tire 21 , while trim components 25 and 26 are for reducing the noise radiated by the rear tire 22.

[0100] Figure 3 shows the same side view of a vehicle according to the invention of Figure 2, zoomed on the region of the rear tire 22. In this Figure, similarly to Figure 1 , line 13 represents the hemi-circle delimiting, together with the tread 33 of the tire 22 and the road surface 30, the front acoustic radiation horn 17 and the rear acoustic radiation horn 18 of the same tire 22. From this Figure, one can appreciate that trim component 25 comprises a surface 31 which faces the tread 33 of the tire 22 and is positioned inside the front acoustic radiation horn 17 of this same tire 22. Surface 31 comprises the tread-facing surface according to the invention for trim component 25. At the same time, trim component 26 comprises a surface 32 which faces the tread 33 of the tire 22 and that is positioned inside the rear acoustic radiation horn 18 of this same tire. Surface 32 comprises the tread-facing surface according to the invention for trim component 26. Both surfaces 31 and 32 are oriented transversally. However, surface 31 is flat, while surface 32 is shaped like an arc of a cylinder in such a way to follow, at least approximately, the profile of the tire towards which it is facing.

[0101] Figure 4 is similar to Figure 3 and shows how to calculate the inclination of a tread-facing surface according to the invention, when this is flat and transversally oriented. In Figure 4, this is exemplified for surface 31 assuming that this coincides with the tread-facing surface for trim component 25 and, in order to make Figure 4 clearer, the rear tire 22 is not shown in it. In order to calculate the inclination of tread-facing surface 31 , two directions have to be considered: the normal direction 35 to treadfacing surface 31 oriented in the outward direction with respect to the volume of the trim component 25 and the longitudinal direction 34. The inclination angle is evaluated as the angle 36 by which the longitudinal direction 34 must be rotated in order to overlap it with the normal direction 35, counted as positive in case the rotation is in the counter-clockwise direction and as negative in case the rotation is in the clockwise direction. For example, the inclination of tread-facing surface 31 in Figure 4 isapproximately -30degrees. It must be noted that the sign of the inclination depends on whether the tread-facing surface is positioned inside the front or the rear acoustic radiation horn of the tire.

[0102] Figure 5a shows an example of a trim component 40 according to the invention. In this Figure, the associated road vehicle is not represented in order to make the Figure clearer. However, the relative positioning of the trim component with regard to the associated road vehicle is obvious based on Figures 2 to 4. The trim component according to the invention 40 shown in Figure 5a has the preferred shape of a wedge. It comprises a sound-absorbing body 41 having a wedge shape too, wherein the base 42 of the wedge is the tread-facing surface. The trim component further comprises a plastic plate 43 covering and materially connected (e.g. glued) to the top surface of sound-absorbing body. Fixation clips 44 are provided on the plastic plate 43 for installation of the trim component 40 onto the associated road vehicle.

[0103] Figure 5b shows another example of a trim component according to the invention 45. Also in this Figure the associated vehicle is not represented in order to make the Figure clearer. The trim component according to the invention 45 shown in Figure 5b has the shape of a truncated wedge and it comprises a sound-absorbing body partially enclosed in a plastic shell 46 covering all surfaces of the sound-absorbing body with the exception of the tread-facing surface 47. In Figure 5b, the only part of the soundabsorbing body that is visible is the tread-facing surface 47. All the other surfaces of the sound-absorbing body are covered by the plastic shell 46. Furthermore, for its installation onto the road vehicle according to the invention, rails 49 are provided along the longitudinal edges of the top surface 48 of the plastic shell 46.

[0104] Figure 5c shows another example of a trim component 50 according to the invention. Also in this Figure the associated vehicle is not represented in order to make the Figure clearer. The trim component according to the invention 50 shown in Figure 5c has the shape of a truncated half-cone and it comprises a sound-absorbing body 51 having this same shape, wherein the base 52 of the sound-absorbing body is the tread-facingsurface and it has the shape of a hemi-circle. The trim component 50 comprises also a plastic plate 53 covering the top surface of the soundabsorbing body 51 and materially connected to it (e.g. glued), as well as brackets 54 for the installation of the trim component 50 onto the road vehicle according to the invention by means of screws.

[0105] Figures 6a to 6e each show a plane section of a sound-absorbing body according to the invention. In all cases, the shape of the sound-absorbing body is the same as that of the wedge-shaped sound-absorbing body according to the invention 41 shown in Figure 5a and the section is cut along a plane normal to the transversal direction, indicated by dashed line AA' in Figure 1.

[0106] The sound-absorbing body according to the invention 60 shown in Figure 6a consists of a body 61 consisting of a first porous fibrous material. The base 62 of the wedge-shaped sound-absorbing body 60 is the tread-facing surface. The material arrangement shown in Figure 6a corresponds to the previously described first embodiment of the sound-absorbing body according to the invention. An alternative embodiment is the one in which the body 61 consists of an open-cell foam instead of a porous fibrous material.

[0107] The sound-absorbing body according to the invention 63 shown in Figure 6b consists of a body 61 consisting of a first porous fibrous material, partially coated with a layer 64 consisting of a second porous fibrous material. The layer 64 coats all the faces of the body 61 with the exception of the top surface 66. In particular, the second porous fibrous material coats the tread-facing surface 65. The thickness of layer 64 is substantially smaller than the dimensions of the sound-absorbing body 63 and of the body 61. The material arrangement shown in Figure 6b corresponds to the previously described second embodiment of the sound-absorbing body according to the invention. Also in this case, alternative embodiments may be obtained by replacing the first and / or the second porous fibrous material with an open cell foam.

[0108] The sound-absorbing body according to the invention 67 shown in Figure 6c differs from the one shown in figure 6b for the fact that an air-permeable foil 68 is inserted between the body 61 consisting of the first porous fibrous material and the layer 64 consisting of the second porous fibrous material. The material arrangement shown in Figure 6c corresponds to the previously described third embodiment of the soundabsorbing body according to the invention. Alternative embodiments may be obtained by replacing the first or the second porous fibrous materials with an open-cell foam and / or replacing the air-permeable film with a thin air-permeable non-woven, known in the field as “scrim”.

[0109] The sound-absorbing body according to the invention 68 shown in Figure 6d consists in a closed shell made with a layer 69 of the second porous fibrous material enclosing an air cavity 70. The material arrangement shown in Figure 6d corresponds to the previously described fourth embodiment of the sound-absorbing body according to the invention. Also in this case, an alternative embodiment may be obtained by replacing the second porous fibrous material with an open-cell foam.

[0110] The sound-absorbing body according to the invention 71 shown in Figure 6e consists of a sound-absorbing body 61 consisting of a first porous fibrous material partially coated with an air-permeable film 67. In particular, the tread-facing surface 71 is coated with the air-permeable film 67. The material arrangement shown in Figure 6e corresponds to the previously described fifth embodiment of the sound-absorbing body according to the invention. Also in this case, alternative embodiments may be obtained by replacing the first porous fibrous material with an open-cell foam and / or by replacing the air-permeable film with a scrim.

[0111]

[0112] In order to assess the effectiveness of the invention here proposed, acoustic tests were carried out on a European F-Segment road vehicle (hereafter referred to simply as "the test vehicle") in three different configurations. The first configuration (hereafter referred to as “Configuration 1”) corresponds to the serial state of the test vehicle, wherein the test vehicle is equipped with a plastic underbody shield with no sound-absorption properties. The second configuration (hereafter referred to as “Configuration 2”) is obtained from Configuration 1 byreplacing the serial plastic underbody shield with a sound-absorptive underbody of the state of the art, realized by means of a layer of a porous fibrous material. The layer has a thickness of approximately 4mm and an area weight of approximately 1200g / m2. The porous fibrous material consists of PET / CoPET bicomponent endless filaments with a fineness of approximately 7denier. The overall area of the underbody shield is about 3m2.

[0113] The third configuration (hereafter referred to as “Configuration 3”) is obtained by Configuration 1 by adding four trim components according to the invention in a manner similar to that shown in Figure 2. All four components were installed on the right side of the vehicle in the direction of travel. The trim components according to the invention all comprised wedge-shaped sound-absorbing bodies realized according to the material arrangement previously described as second embodiment. More specifically, each sound-absorbing body according to the invention consisted in a body consisting of a first porous fibrous material completely coated with a layer consisting of a second porous fibrous material. The first porous fibrous material had a density of approximately 30kg / m3and consisted of PET staple fibers having a length of about 50mm and a fineness comprised between 0.5 and 2denier. The layer of the second porous fibrous material had a thickness of about 4mm and an area weight of about 1200g / m2. Its bending modulus was about 250MPa and it was sufficient to confer to the trim components a self-supporting character. The second porous fibrous material consisted in bicomponent PET / CoPET endless filaments with a fineness of about 7denier. All four soundabsorbing bodies featured flat tread-facing surfaces oriented in a transversal way an inclination between -30degrees and -20degrees for the tread-facing surfaces partially positioned inside the front acoustic radiation horns and between +20degrees and +30degrees for the tread-facing surfaces partially positioned inside the rear acoustic radiation horns. All trim components had a longitudinal dimension of approximately 300mm, a transversal dimension of about 220mm and a vertical dimension of about 70mm and were fixed to the test vehicle by means of clips. The totalweight of the four trim components according to the invention is approximately 1.2kg. For each trim component according to the invention, the distance between the tread-facing surface and the tire tread towards which it was facing was between 70mm and 100mm.

[0114] In order to assess the impact of the trim components according to the invention on exterior noise, the External Acoustic Transfer Function (EATF) was measured in all three Configurations as follows. 15 microphones were arranged along a line parallel to the longitudinal axis of the test vehicle and at a distance of 7.5m from this same axis on the right side of the vehicle in the direction of travel, as shown in Figure 7. All microphones are positioned at a height of 1.2m from the ground. These geometrical dimensions correspond to the prescriptions of the test procedure according to the ECE 51.03. An acoustic volume velocity sound source was positioned at four points in correspondence of the leading and trailing edge of the tire contact patch of the front and of the rear tire on the right side of the test vehicle. Figure 8 shows the two source positions 80 and 81 for the rear tire 22, being the two positions for the front tire analogous. For each of the four source positions and of the fifteen microphone positions, the transfer function between the source acoustic volume velocity and the acoustic pressure at the microphone is measured. In total, 60 transfer functions are measured. The External Acoustic Transfer Function is then obtained as an energetic average of these sixty transfer functions.

[0115] Figure 9 compares the EATFs obtained for the three Configurations for the frequency range between 400Hz and 2000Hz. As one can see, the reduction (i.e. the improvement) in EATF obtained thanks to the trim components according to the invention ("Configuration 3", dashed line) with regard tothe serial car ("Configuration 1", solid line) is comparable with that obtained thanks to the state of the art sound-absorptive underbody shield (“Configuration 2”, dash-dotted line) and it is in the order of 1dB. This is true, in particular, over the frequency range between 800Hz and 1600Hz, which is the most relevant for exterior tire noise.However, this comparable performance is obtained with a substantial saving in terms of material and weight.

[0116] In order to assess the impact of the trim components according to the invention on interior noise, the Interior Acoustic Transfer Function (IATF) was measured in all three Configurations as follows. One microphone was positioned in correspondence of the center of the head of the front passenger. An acoustic volume velocity source was positioned at the same 4 positions used for the evaluation of the EATF. For each source position, the transfer function between the acoustic volume velocity of the source and the acoustic pressure at the microphone was measured. In total, four transfer functions were measured. The IATF is obtained as an energetic average of these four transfer functions.

[0117] Figure 10 compares the lATFs obtained for the three Configurations for the frequency range between 400Hz and 5200Hz. As one can see, the reduction (i.e. the improvement) in IATF obtained thanks to the trim components according to the invention ("Configuration 3", dashed line) with regard to the serial car ("Configuration 1", solid line) is substantially higher than that obtained thanks to the state of the art sound-absorptive underbody shield (“Configuration 2”, dash-dotted line), in spite of a substantial saving in material and weight.

Claims

ClaimsClaim 1. Vehicle travelling on road and comprising tires, each tire with a tread formed by its outer surface in regular contact with the road the vehicle is travelling on and forming with it a front and a rear acoustic radiation horn, the vehicle further comprising a trim component for reducing noise radiated by said tires, characterized in that the trim component comprises an inherently three-dimensional sound-absorbing body, which has a maximum dimension lower than 800mm and an aspect ratio lower than 10, and whereby at least part of the sound-absorbing body surface is opposite and facing the tread of a tire and whereby said at least part of the soundabsorbing body surface is positioned at least partially inside either the front or the rear acoustic radiation horn of said tire.Claim 2. A vehicle according to claim 1 , characterized in that the trim component is mounted onto or integrated into a longitudinal rocker or it is mounted onto or integrated into a bumper of the vehicle.Claim 3. A vehicle according to claim 1 or claim 2, characterized in that the minimum distance between said at least part of the sound-absorbing body surface and the tread of the tire it is facing is between 20mm and 150mm, preferably between 30mm and 100mm, more preferably between 40mm and 70mm.Claim 4. A vehicle according to any of the preceding claims, characterized in that the minimum distance between the trim component and the road is between 20mm and 150mm, preferably between 40mm and 100mm, more preferably between 50mm and 80mm.Claim 5. A vehicle according to any of the preceding claims, characterized in that the trim component further comprises a plastic shell at least partially coating the sound-absorbing body.Claim 6. An automotive trim component for use in a vehicle according to any of the preceding claims for reducing the noise radiated by the tires of said vehicle, characterized in that it comprises an inherently three-dimensional sound-absorbing body having dimensions lower than 800mm and an aspect ratio lower than 10, whereby at least part of the surface of the soundabsorbing body is for facing the tread of a tire when mounted on a vehiclesuch that said at least part of the surface of the sound-absorbing body is positioned at least partially inside the front or the rear noise acoustic radiation horn of said tire.Claim 7. An automotive trim component according to claim 6, characterized in that the trim component has the shape of a wedge or of a half-cylinder, or of a half-cone, or of a half-truncated cone or of a tapered polyhedron.Claim 8. An automotive trim component according to claim 6 or claim 7, characterized in that the dimension of said at least part of the surface of the sound-absorbing body in the transversal direction is at least 120m, preferably at least 180mm, more preferably at least 220mm.Claim 9. An automotive trim component according to claims 6 to 8, characterized in that said at least part of the surface of the sound-absorbing body has the shape of an arc of a cylinder or is flat and oriented in the transversal direction with an inclination comprised between +60degrees and -60degrees.Claim 10. An automotive trim component according to any of claims 6 to 9, characterized in that the sound absorbing body comprises a body consisting of a first sound-absorbing material.Claim 11. An automotive trim component according to any of claims 6 to 9, characterized in that the sound absorbing-body comprises a body consisting of a first sound-absorbing material, at least partially coated with a layer consisting of a second sound-absorbing material.Claim 12. An automotive trim component according to any of claims 6 to 9, characterized in that the sound-absorbing body comprises a body consisting of a first sound-absorbing material, at least partially coated with an air-permeable foil or a scrim.Claim 13. An automotive trim component according to claim 12, characterized in that the body consisting of a first sound-absorbing material at least partially coated with an air-permeable foil or scrim is at least partially coated with a layer consisting of a second sound-absorbing material.Claim 14. An automotive trim component according to claims 6 to 9, characterized in that the sound-absorbing body consists of a closed shell consisting of a sound-absorbing material.

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