Classifications

• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
  • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects

Definitions

• the invention relates to a sound absorbing means which contains at least one cavity resonator.
• Sound absorbing materials are generally used in many different fields and their main task is to provide hygiene of the environment from the point of view of undesired or harmful sound.
• the design of a sound absorbing material suitable for the application is based on a range of frequencies of unwanted sound, which is to be absorbed or damped.
• porous materials such as melamine, polyurethane and metal foams or non-woven fabrics made from mineral or polymeric fibers. Nevertheless, for absorbing sounds of lower frequencies are these materials unsuitable, due to great thickness of materials needed in such cases.
• the general objective is to combine the above-mentioned characteristics into one acoustic system, which would be able to absorb sounds of low as well as of high frequencies.
• a layered sound absorbing non-woven fabric which comprises a layer of nanofibers having with diameter up to 600 nanometers and a surface weight of 0,1 to 5 g/m 2 andat least another layer of fibrous material, these layers being formed by cross laying.
• the layer of nanofibers fulfils the function of acoustic resonant membrane resonating at low frequency, whereas the layer of another material provides not only sufficient damping, by which means the maximum quantity of sound energy gathered in the resonator is converted into heat, but at the same time it is capable of absorbing sounds of higher frequencies.
• this textile absorbs with good results especially sounds of frequencies in relatively narrow range from approximately 700 to 1300 Hz.
• the goal of the invention is therefore to eliminate or at least reduce the disadvatages of the present state of the art and to propose sound absorbing means that would be capable of absorbing with good results sounds in as broad frequency range as possible.
• the goal of the invention is achieved by sound absorbing means which contains at least one cavity resonator, whose principle consists in that on at least one of the surfaces of this cavity resonator is fixedly attached an acoustic resonant membrane, which overlaps an orifice/orifices leading into the cavity/cavities of the cavity resonator.
• the parameters of the resonant membrane together with the shape and volume of the cavity of the cavity resonator then determine which sound frequencies will be damped and to what extent. At the same time it is possible - while keeping the thickness of the resonator - to damp sound frequencies which could be normally damped by cavity resonator with extremely large air gap.
• the resonant membrane is arranged on both opposing surfaces of the cavity resonator and/or on the resonant membrane there is arranged another cavity resonator on which can be fixedly attached another resonant membrane, which overlaps the orifice/orifices leading into its cavity/cavities.
• any cavity resonator can be used as the cavity resonator, for example a Helmholtz cavity resonator, a cavity resonator formed by honeycomb, a cavity resonator formed by perforated panel/board with at least one cavity, etc.
• any resonant membrane can be then used as the resonant membrane, for example a layer of polymeric nanofibers, a synthetic foil, a metallic foil, a cellulose foil, a layer of paper, or a combination thereof, etc.
• the resonant membrane can also be perforated.
• the resonant membrane is preferably provided with reinforcement from group of: a grid, a net, a layer of textile, a net of points and/or linear and/or planar formations of materials in solid state, etc.
• a covering layer is arranged, the covering layer from group of: a grid, a net, a layer of textile, a foam, a synthetic foil, a metallic foil, a layer of lightweight building material, a layer of paper, a layer of cardboard, a layer of plywood, a layer of chipboard, a layer of wood, a layer of glass, or combinations thereof.
• At least one cavity of the cavity resonator is at least partially filled with sound absorbing material from group including an aerogel, a material containing aerogel as one of its components, polymeric nanofibers, a layer of polymeric nanofibers, a material containing polymeric nanofibers or a layer of polymeric nanofibers as one of its components, a fibrous layer, a layer formed by meltblown technology, a foam, a gas cushion, a bubble foil, a polymeric granulate, a foil filled with a liquid, a composite material, fibers, twists of a fibrous layer, including a layer of polymeric nanofibers, bunches of nanofibers, or shreds of a layer of nanofibers, twists of paper, slips of paper, a vermiculite granulate, wood chips and/or wood sawdust, a perlite, chopped straw and/or chaff, feather, a sand, balls or other formations of polyester, or combinations thereof.
• sound absorbing material from group including an aerogel
• Fig. 1 schematically shows a cross section of sound absorbing means according to the invention with Helmholtz cavity resonator
• Fig. 2 shows a cross section of another embodiment of sound absorbing means according to Fig. 1
• Fig. 3 showsa cross section of sound absorbing means according to the invention with cavity resonator formed by honeycomb
• Fig. 4 shows a cross section of sound absorbing means according to the invention with cavity resonator formed by perforated board
• Fig. 5 shows a cross section of sound absorbing means according to the invention with two cavity resonators formed by perforated board
• Fig. 6 shows a graph of sound absorption coefficient a of the sound absorbing means according to the invention and its separate components
• Fig. 1 schematically shows a cross section of sound absorbing means according to the invention with Helmholtz cavity resonator
• Fig. 2 shows a cross section of another embodiment of sound absorbing means according to Fig. 1
• Fig. 3 shows a cross section of sound absorbing means according
• FIG. 7 shows a graph of sound absorption coefficient a of the sound absorbing means according to the invention, different from the one represented in Fig. 6, and of its separate components
• Fig. 8 shows a graph of sound absorption coefficient a of the sound absorbing means according to the invention different from the ones shown in Fig. 6 and Fig. 7, and of its separate components.
• the principle of the invention consists in usageof combination of a cavity resonator, by which the air or other material contained in its cavities is forced into vibration upon impact of sound waves of high frequency, and an acoustic resonant membrane, which is brought into forced vibration upon impact of sound waves of low frequency.
• any known cavity resonator can be used, such as:
• a Helmhoitz cavity resonator whose perforated board can be made, for example, of plastic, paper, cardboard, wood, plywood, veneer, metal, plasterboard, etc., or combination thereof,
• honeycomb a cavity resonator formed by honeycomb, which can be made, for example, of plastic, paper, cardboard, wood, plywood, veneer, metal, etc., or combination thereof,
• All the cavities of the resonator, or the inlet orifices leading into them, can have the same shape and size, or at least some of them differ in at least one of these parameters.
• at least some of the cavities of the cavity resonator can be - as the need may be - at least partially filled with sound absorbing material.
• such materials may be for example:
• a gas cushion for example, air or some other gas enclosed in polyethylene foil according to Cell-O® technology
• a composite in general sence ofsolid particles embedded in a matrix
• m twists and/or bunches and/or slips of a fibrous layer, including a layer of polymeric nanofibers
• the cavity resonator can be underlayed by layer of suitable sound absorbing material, or it can be supplemented by such layer, which is arranged between it and the surface, to which the sound absorbing means according to the invention is applied or on which it is laid.
• the resonance frequency of the cavity resonator is then determined especially by dimensions of its cavity/cavities, by size and shape of the inlet orifices leading into it/them, by its material and by the quantity and character of the fillings of the cavity/cavities.
• the cavities of the cavity resonator are usually closed from one side by the surface of the base, to which the sound absorbing means according to the invention is to be applied, however, if necessary, they can be closed by suitable layer of material, for example the same material from which the whole body of the cavity resonator is made.
• acoustic resonant membrane As the acoustic resonant membrane can be used, for example:
• a separate layer of polymeric nanofibers which consists of polymeric nanofibers of one type, or of several types differing in material and/or the diameter of the nanofibers and/or orientation of the nanofibers,
• a layer of polymeric nanofibers which is created from polymeric nanofibers of one type, or of several types differing from each other in material and/or diameter of nanofibers, which is arranged on suitable support layer, on which it was deposited during its production through electrostatic spinning or on which it was transferred during its production, such as for example a textile, a grid, a net, metal or plastic foil (e.g.
• a layer of foam material a layer of aerogel, a layer comprising aerogel as one of its components, etc., or on another support layer comprising any combination of these materials, whereby it can be connected with this underlying layer, for example by means of suitable binder and/or by lamination, the support layer is then arranged in direction towards the cavity resonator or away from it,
• a layer of polymeric nanofibers which is created from polymeric nanofibers of one type, or of several types differing from each other in material and/or diameter of nanofibers, and which comprises a reinforcement arranged at least on part of at least one of its surfaces, such as for example a grid or a net, which can be connected with the layer of polymeric nanofibers, for example by means of suitable binder and/or by lamination, and/or it comprises a net of formations (points, fibers, bands, planar formations, etc.) of material in solid state, which at least partially penetrate into the thickness of the layer of polymeric nanofibers and enwrap part of its nanofibers and/or are at least partially enwrapped by the material of nanofibers and/or are connected to the nanofibers due to their adhesive properties, whereby this layer of polymeric nanofibers can be arranged on suitable support layer (see e.g. point b)),
• a synthetic foil for example from expanded polytetrafluorethylene, which is according to specific requirements homogeneous or perforated and which can be also - if needed - provided with a reinforcement, such as for example a grid or a net, which can be connected to the foil, for instance by means of suitable binder and/or by lamination for example,
• a cellulose foil which is according to specific requirements homogeneous or perforated and which can be in case of need provided with a reinforcement, such as a grid or a net or a layer of textile, which can be connected with the layer of polymeric nanofibers by means of suitable binder and/or by lamination for example,
• a layer of paper which is according to specific requirements homogeneous or perforated, and which can be, if needed, provided with a reinforcement, such as for example a grid, a net or a layer of textile, which can be connected with the layer of paper by means of suitable binder and/or by lamination for example, i) a fibrous layer consisting of fibers of one type or several types differing in material and/or diameter of nanofibers, which can be, if needed, provided with a reinforcement, such as a grid, a net or another layer of textile,
• any layer/layers according to the points a) to i) any of which is provided with suitable surface treatment, for example for increasing flame resistance and/or water resistance and/or electrical conductivity, and/or it is provided with plasma treatment and/or spray application and/or spreading, etc.
• any of these acoustic resonant membranes can be combined with any of the above mentioned cavity resonators.
• This resonant membrane is then arranged on the surface of the cavity resonator, to which it is fixedly attached, for example glued or laminated, etc. Its parts, which overlap the orifices leading into the cavity/cavities of the cavity resonator, constitute separate resonant surfaces, whereby the resonant frequency of each of them is determined, apart from the overall properties of the resonant membrane, also by their size and shape.
• these resonant surfaces Upon impact of sound waves, these resonant surfaces are brought into forced vibrations, which are subsequently damped by friction in the inner structure of the resonant membrane, by the friction of the resonant membrane against ambient air and possibly against other layers of the material arranged in its proximity, wherein part of the kinetic energy of the resonating membrane is transmitted to the cavity resonator. Moreover, friction in the inner structure of the resonant membrane is further increased by the fact that the neighbouring resonant surfaces can vibrate with mutually different period and/or deviation.
• one covering layer of material can be arranged, which protects the resonant membrane from mechanical damage, and, as the case may be, it constitutes or partly constitutes the front side of the sound absorbing means according to the invention.
• the covering layer for example, the following materials can be used:
• a layer of light-weight building material such as polystyrene
• this covering layer may be attached to the resonant membrane by means of suitable binder, such as melt binder and/or by lamination.
• suitable binder such as melt binder and/or by lamination.
• at least one layer is arranged between the cavity resonator and the resonant membrane, or the resonant membrane is arranged between two covering layers.
• the sound absorbing means comprises a Helmholtz cavity resonator composed of a cavity i defined by an outer frame 2 arranged on the base 3, to which the sound absorbing means is to be applied, by the surface 31 of this base 3 and by perforated wooden board 4 having a thickness of 5 mm located at distance of 20 mm from the surface 3J. of the base 3. All the orifices 41 in the perforated board 4 have circular shape and identical size or area of 7 mm 2 , whereby the area of the resonator is 200 mm 2 . From the outer side on the perforated board 4 is arranged, e.g.
• a resonant membrane 5 formed by layer of polyamide nanofibers having a surface weight of 0,4 g.m "2 , and average diameter of nanofibers of 250 nm, which overlaps its entire surface, including the orifices 4J_ which lead into the cavity of the resonator.
• the resonant surfaces 51 of the resonant membrane 5, which are arranged within the spaces of the orifices 41 of the perforated board 4 are brought into forced vibration by the components of the sound waves with low frequency. Their vibrations are at the same time damped especially by the friction in the inner structure of the resonant membrane 5, its friction against ambient air and against the perforated board 4, and also by transmission of part of the kinetic energy on the perforated board 4 and on the outer frame 2 of Helmholtz resonator, or to other not shown assembly and/or construction elements, by which the sound absorbing means according to the invention is attached to the support 3, and, as the case may be, also to the base 3.
• Components of the sound waves with higher frequency then pass through the resonant membrane 5 and the orifices 41_ in the perforated board 4 to the cavity 1 of Helmholtz resonator, where they bring molecules of air into forced vibrations. Vibration of these molecules is then damped by their mutual friction and friction against walls of the Helmholtz resonator or also against the resonant membrane 5. In this manner components of sound waves in broad band of frequencies are absorbed simultaneously.
• a sound absorbing material such as a textile (Fig. 2), or combination of these materials.
• the outer frame 2 of Helmholtz resonator is in the embodiments shown in Fig. 1 and Fig. 2 formed by independent element fitted with not shown means for connection to the surface 31 of the base 3, to which the sound absorbing means according to the invention is to be applied, nevertheless in not shown embodiments it can be formed directly by part of this base 3, for example by its construction element/elements, etc.
• a cavity resonator is used, formed by honeycomb 6.
• the cavities, or orifices leading into the cavities of this resonator, are enclosed by the surface 31 of the base 3, to which the sound absorbing means according to the invention is to be applied, and from the opposite side by the resonant membrane 5 formed by layer of polymeric nanofibers arranged on an support textile 52 of spunbond type.
• the support textile 52, on which the layer of polymeric nanofibers was deposited during its production through electrostatic spinning, is arranged in direction away from the cavity resonator, thus protecting the resonant membrane 5 from mechanical damage and at the same time contributing to absorbing components of sound waves with higher frequencies.
• This sound absorbing means is based on the same principle as the sound absorbing means shown in Fig. 1 - i.e. the components of the sound waves with low frequencies are absorbed by the vibrations of the resonant membrane 5, and the components of the sound waves with high frequencies are absorbed by the cavity resonator, and, as the case may be, by the support textile 52.
• the components of the sound waves with low frequencies are absorbed by the vibrations of the resonant membrane 5
• the components of the sound waves with high frequencies are absorbed by the cavity resonator, and, as the case may be, by the support textile 52.
• at least some cavities of the cavity resonator are at least partially filled with suitable sound absorbing material mentioned above.
• a cavity resonator formed by perforated panel 7 is used.
• the cavities or orifices leading into the cavities of this resonator are enclosed by the surface 31 of the base 3, to which the sound absorbing means according to the invention is to be applied, and from the opposite side by the resonant membrane 5 formed by layer of polymeric nanofibers.
• the resonant membrane 5 is overlapped from the outer side by covering layer 53 formed by polystyrene panel with open structure, which at the same time constitutes the frontside of the sound absorbing means and which is connected with the resonant membrane by means of binder through points or abscisae, or in another manner which enables vibration of the resonant membrane 5 or its parts.
• This sound absorbing means is based on the same principle as in the preceding embodiments - i.e. components of the sound waves with low frequencies are absorbed by the vibration of the resonant membrane 5, while the components with high frequencies are absorbed by the cavity resonator, and possibly also by the covering layer 53.
• At least some cavities of the cavity resonator are at least partially filled with suitable sound absorbing material mentioned above.
• Fig. 5 further shows an embodiment of sound absorbing means according to the invention in which the cavity resonator is formed by perforated panel 7, whose cavities or orifices leading into the cavities are enclosed by the surface 3J. of the base 3, to which the sound absorbing means according to the invention is to be apllied, and from the opposite side are enclosed by resonant membrane 5 composed of layer of polymeric nanofibers.arranged another identical cavity resonator formed by perforated panel 70, to which is fixedly attached another identical resonant membrane 50, which overlaps the cavities or orifices leading into the second cavity resonator.
• the outer resonant membrane 50 is from the outer side overlapped by covering layer 501 formed in the shown embodiment by textile layer, which at the same time constitutes the frontside of this sound absorbing means.
• At least some cavities of the cavity resonator are at least partially filled with suitable sound absorbing material mentioned above.
• the resonant membrane 5 is arranged on one surface of the cavity resonator, nevertheless in not shown embodiments the same or different resonant membrane 5 can be arranged on both opposing surfaces of the cavity resonator, whereby at least on one of its surfaces a plurality of resonant membranes 5 can be arranged, the resonant membranes being either in contact or being separated from each other by at least one layer of suitable material, such as textile, a grid, a net, an air gap, etc.
• suitable material such as textile, a grid, a net, an air gap, etc.
• Arranged further on the surface 31_ of the base 3 and/or in its proximity can be not shownsupport layer, which encloses the cavities of the resonators from this side, and, as the case may be, it also contributes to sound absorption.
• Fig. 6 shows a graph of the sound absorption coefficient a in dependence on frequency of sound for sound absorbing means which comprises cavity resonator formed by paper honeycomb with the dimension of the mesh of 9 mm, on which on its whole surface is arranged and fixedly attached resonant membrane 5 formed by layer of polymeric nanofibers made from polyamide having surface weight of 0,2 g.m "2 , which is over the whole surface overlapped by covering layer 53 composed of non-woven textile with surface weight of 20 g.m “2 .
• the total thickness of the sound absorbing means is 18 mm.
• the sound absorption coefficient a of this sound absorbing means is greater than mere sum of sound absorption coefficients a of the separate components (V - cavity resonator, VO - cavity resonator with covering layer).
• the sound absorption coefficient a in this embodiment achieves values that are higher than 0,6 for sounds with frequencies approximately from 950 Hz and for sounds with higher frequency approximates its value to .
• Fig. 7 shows a graph of sound absorption coefficients a in dependence on the frequency of sound for separate plastic board having diameter of orifices of 5 mm and spacing between orifices of 10 mm, which is 25 mm from the surface 31 of the base 3 (i.e. separate Helmholtz resonator) - the grey curve, as well as for sound absorbing means comprising this resonator, whose surface is overlapped by acoustic resonant membrane 5 formed by layer of nanofibers from polyamide 6 (PA6) having surface weight of 12,5 g.m "2 , which is laminated onto the plastic board - the black curve.
• PA6 polyamide 6
• a Helmholtz resonator where the space between the board and the surface 31 of the support 3 is filled with the above described polyurethane foam - the dark grey curve, and for the sound absorbing means comprising this resonator with a filling, the surface of the resonator being overlapped by acoustic resonant membrane 5 formed by layer of nanofibers from polyamide 6 (PA6) having surface wieight of 12.5 g.m "2 , which is laminated onto the plastic board.
• PA6 polyamide 6
• the sound absorbing means according to the invention can be used, for example, for the production of acoustic bodies, interior blinds, wallpapers, tiling, ceilings, screens, curtains and separating walls for interiors, or, as the case may be, segment or profile elements for the transportation industry (e.g. door panels, fender shields, paneling of hood or engine compartment or a cabin), materials for noise reduction for noisy devices, for the production of earphones, etc.
• segment or profile elements for the transportation industry e.g. door panels, fender shields, paneling of hood or engine compartment or a cabin
• materials for noise reduction for noisy devices for the production of earphones, etc.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Multimedia (AREA)
• Building Environments (AREA)
• Soundproofing, Sound Blocking, And Sound Damping (AREA)

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Cited By (14)

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Family Cites Families (8)

• 2013
  • 2013-01-18 CZ CZ2013-35A patent/CZ304657B6/cs unknown
• 2014
  • 2014-01-16 WO PCT/CZ2014/000008 patent/WO2014111068A2/en active Application Filing
  • 2014-01-16 EP EP14705963.8A patent/EP2875506B1/en not_active Not-in-force

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