Anechoic broadband compact (ABC) muffler formed of layered, parallel, strips with moving blade, construction, and vehicle applications

Abstract

A muffler is formed of sheets of spaced, parallel, strips of material (150,152,154,156) two or more such adjacent sheets have strips oriented in at least two directions forming holes (158,160) where spaces between strips align; in an embodiment two such layers are closely spaced with holes not aligned forming narrow channels between holes with an optional spacer layer. In another embodiment, valleys between strips serve as narrow channels between holes of a first layer and a second adjacent layer. In embodiments, the narrow channels have dimensions no more than twice the Stokes boundary layer thickness at a frequency at which attenuation is desired. In embodiments, the muffler may be disposed on a wall to absorb sound, about machinery needing quieting, or on a surface of a blade of a fan, propeller, wing, helicopter rotor, or wind turbine. The muffler may also be used to quiet a centrifugal blower or a vehicle.

Description

Atty Docket No. TUOE.P2015WO / 00679628Anechoic Broadband Compact (ABC) Muffler Formed of Layered, Parallel, Strips with Moving Blade, Construction, and Vehicle ApplicationsCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application benefits from and claims priority to U.S. Provisional Patent Application No. 63 / 764,764, entitled ‘Anechoic Broadband Compact (ABC) Muffler Formed of Layered, Parallel, Strips with Moving Blade, Construction, and Vehicle Applications,’ filed on February 28, 2025, the entire disclosure of which is hereby incorporated by reference herein.BACKGROUND

[0002] Sound mitigation is important for addressing the noise challenges posed by many devices including airplanes and wind turbines. Most noise generated by airplane wings are ultra-low frequencies (below 100 Hz). Wind turbines and HVAC systems generate noise typically between 20 and 400 Hz. These low and mid-frequency noises are a significant concern due to their heightened annoyance factor compared to higher-frequency noise. Published measurements of infrasound (noise at frequencies less than 20 Hz) indicate that levels at typical residential set-back distances from wind farms may be too low to be directly audible but may be perceived through window rattling. Low-frequency noise levels in the frequency range of 20-200 Hz may also exceed audibility thresholds and be annoying or interfere with conversations, leading to complaints, public opposition, and legal challenges, hindering further expansion of wind power projects. Moreover, low- and mid-frequency noises pose health risks to nearby residents, including sleep disturbances, stress, and potential cardiovascular and cognitive effects.

[0003] Sound propagating through media other than air can also cause issues and require damping. For example, much submarine detection and antisubmarine warfare relies on detection of sound emitted by submarines and propagated through water; such noises can be emitted by both unducted and ducted propellers or thrusters of the submarine as well as internal machinery. Similarly, engines and propellers of boats and ships may emit sounds for which damping can be desirable; lateral thrusters of cruise ships can disturb passengers during docking and undocking procedures.

[0004] In addition to air and water, sound can propagate through other media such as oil; many of these media require pumping that can produce sound. Similarly, heavy-duty power transformers often vibrate at powerline frequencies of 50 Hz or 60 Hz, or harmonics thereof; these vibrations can also produce objectional sounds.Atty Docket No. TUOE.P2015WO / 00679628

[0005] Typically, passive mufflers contain Helmholtz resonators; quarter-wave resonators; duct area expansions (this relates to horns with a gradual or stepwise increase of the wave front area); aerodynamic modifications, acoustic absorbing materials (fibrous, porous, reticulated, micro-perforated, etc.), and “acoustic black hole” constructions (typically incorporating a range of discs with holes of decreasing diameters separated by cavities).SUMMARY

[0006] A muffler is formed of sandwiches of layers each formed of closely-spaced or adjacent sheets. In an embodiment, each sheet is formed of multiple, gapped, parallel strips of a material. Strips may also be referred to as slats herein. Sheets of each layer are stacked adjacent with the parallel strips of a first sheet at a nonzero angle relative to the parallel strips of a second sheet such that holes or openings are formed where gaps between the first and second sheet align. In embodiments the angle may be 30, 45, 60, or 90 degrees; this produces a layer with holes and ridges with valleys, the ridges formed of strips with the valleys between ridges formed by the gaps between parallel strips. Two or more such layers are either closely spaced with all, or in some embodiments a majority of, their holes misaligned so that the layers form a sandwich with the layer spacing forming narrow channels between holes, or in some embodiments a sandwich is formed with the ridges of two or more adjacent layers attached or fused together so the valleys serve as channels between holes of the layers.

[0007] In an alternative embodiment, the parallel strips are woven to form each layer. In some alternative embodiments, a sandwich is positioned ahead of a back cavity; and in other alternative embodiments two sandwiches with differing characteristics are effectively placed in series to absorb a broad spectrum of sound.BRIEF DESCRIPTION OF THE FIGURES

[0008] Fig. 1A is a top view of a single layer of a flat muffler formed of two sheets each formed of gapped, parallel, strips of material, with the top sheet shown as semi-transparent, and showing holes through the layer formed by the gaps between strips.

[0009] Fig. IB is top view of a muffler formed of two layers, each layer as illustrated in Fig. 1A, with the holes of a top layer not aligned with holes of a bottom layer.Atty Docket No. TUOE.P2015WO / 00679628

[0010] Fig. 1C is a schematic cross section of a muffler of Fig. IB, as formed according to Fig. 1A and IB with a spacer layer between two layers, each layer formed as per Fig. 1A.

[0011] Fig. ID is a schematic cross section of a muffler as formed according to Fig. 1 A and IB, where the valley formed of gaps between strips of one layer is half the required thickness for channels, and the adjacent valleys of two layers are aligned and fused.

[0012] Fig. IE is a schematic cross section of a muffler formed of three sheets of strips, a first and third oriented in one direction and a second at angles to the first and third sheets of strips, forming channels between effective holes along gaps between layers of the second sheet of strips.

[0013] Fig. IF is a schematic cross section of a flat muffler formed of as in Fig. IB showing an optional back cavity.

[0014] Fig. 2A is a cross section of a dome-shaped muffler showing an optional back cavity.

[0015] Fig. 2B is an exploded view of an embodiment of an acoustic assembly including a back cavity or chamber positioned posterior to a muffler, in embodiments.

[0016] Fig. 3 A is a comparison of flat mufflers as herein described having a 35 mm backspace and formed of various materials to various conventional sound-dampening materials.

[0017] Fig. 3B is a comparison of flat mufflers as herein described with a variety of backspaces depths.

[0018] Fig. 4A is a schematic representation of a muffler according to the present disclosure.

[0019] Fig. 4B is a schematic view illustrating another embodiment of a muffler in a rolled form.

[0020] Fig. 5 is a schematic of a commonly-used blade design for wind turbines with a section taken near the tip of the blade, including an acoustic muffler according to embodiments.

[0021] Fig. 6 is a perspective view of a wireframe model of the airfoil section near the tip of the blade of Fig. 5.

[0022] Fig. 7 is an illustration of axial fans having the muffler on the blades.

[0023] Fig. 8A is an illustration of a vehicle with muffler sections incorporated in the hood of a vehicle and / or into a shroud over a rear wheel of the vehicle.Atty Docket No. TUOE.P2015WO / 00679628

[0024] Fig. 8B an illustration of a vehicle with a muffler section incorporated in a side panel of a vehicle.

[0025] Fig. 9A, 9B, and 9C illustrate placement of the muffler on a compressor of heat pump unit.

[0026] Fig. 10 illustrates use of the muffler to quiet centrifugal blowers.

[0027] Fig. 11A is a lateral view of a muffler constructed of overlapping parallel strips or slats of material.

[0028] Fig. 1 IB is a top view of the muffler of Fig. 11 A.

[0029] Fig. 11C is a lateral view of a switchable variation of the muffler of Fig.11 A and 1 IB in a non-attenuating mode.

[0030] Fig. 11D shows schematically a cross section of another exemplary embodiment of a muffler assembly including parallel strips or slats.

[0031] Fig. 12 is a view of a wall hanging or artwork implementation of the muffler described herein with a back chamber having a low-density sound absorbing material to broaden frequency response.

[0032] Fig. 13 illustrates frequency dependence of a muffler having various molecular weights of gas fill.

[0033] Fig. 14A and 14B illustrate frequency response of a muffler constructed of various materials according to Fig. 1 A-1F without a back cavity.

[0034] Fig. 14C illustrates frequency response for a muffler having a variety of back cavity depths.

[0035] Fig. 15A illustrates frequency dependence of a muffler having a back cavity of 55 mm with a range of air pressure in the back cavity.

[0036] Fig. 15B illustrates frequency dependence of a muffler of Fig. 12 having a back cavity filled with a light sound-absorbing material.

[0037] Fig. 16 illustrates an alternative embodiment where strips of two sheets of a layer of a muffler are W-shaped instead of being straight.

[0038] Fig. 17 depicts a muffler according to embodiments disposed on a first surface of a mass of open cell porous concrete.

[0039] Fig. 18A illustrates a pipe or duct having a muffler structure enclosed by the first conduit, in embodiments.

[0040] Fig. 18B illustrates a pipe or duct having a muffler structure integrated into at least a portion a wall of the first conduit and enclosed by an outer second conduit, in embodiments.Atty Docket No. TUOE.P2015WO / 00679628DETAILED DESCRIPTION OF THE EMBODIMENTSMuffler Theory

[0041] The present disclosure describes an ultra-thin muffler and applications for that muffler to solve the problem of ultra-low frequency (below 100 Hz) and low-frequency (100-1000 Hz) noise emitted by wind turbines and airplanes during their operation, as well as noises from many other devices including HVAC systems such as heat pumps, boilers, blowers, and ventilation units. Further, the muffler can be used to reduce radiated noise from industrial plants, and to help insulate hotel rooms and apartment units from outside noises and noises from adjacent rooms or units. In particular, the ultra-thin muffler may be used as an acoustic tape to quiet various fixed and moving structures such as aircraft wings, helicopter blades, propellers, blowers, and fan blades, gas turbine blades, and ship propellers, potentially including fan blades of turbofan engines, various vehicles and aircraft. Additionally, the present muffler can function as a versatile acoustic material, which may be referred to as an acoustic panel, acoustic jacket, acoustic cover, or acoustic coating. It can be implemented as an independent element or integrated component in systems, devices, and structures such as: Walls, wallpaper, tiles, and ceilings in construction for noise reduction in buildings that could be made from transparent material; silent rigid bodies; thin acoustic separator walls for soundproofing between areas; noise barrier in highways, and household appliance bodies and casings in order to effectively reducing operational noise. This innovation provides a lightweight, space-efficient, and highly effective noise reduction solution, offering a superior alternative to conventional acoustic panels, rigid enclosures, and insulation materials.

[0042] An exemplary muffler 100, 200 is formed of sandwiches of layers, each layer formed of sheets each formed of multiple, closely-gapped, parallel strips 150, 152 of a material as shown in Fig. 1 A, strips of at least two sheets oriented at an angle to each other such that holes 158 are formed by overlaps of gaps between the strips.

[0043] In embodiments, the material of the strips is selected according to a particular application. For example, mufflers exposed to hot exhaust gasses may be made of metal, such as stainless steel or higher temperature alloys, or, for somewhat lower temperatures, aluminium, while those in less extreme environments may be formed of materials such as fiber including cellulose flax, hemp, kenaf, jute, cotton, and similar fiber, wood and wood composites, plastic including bioplastics and filled plastics likeAtty Docket No. TUOE.P2015WO / 00679628fiberglass or carbon-fiber composites, or even cardboard composites. In some embodiments, these materials may be recycled materials such as recycled polyethylene terephthalate.

[0044] Multiple-parallel-strip sheets of the muffler are stacked in layers, each layer having a first sheet of first parallel strips 150 at a nonzero angle relative to a second sheet of second parallel strips 152. The angle may be selected according to the application. In embodiments the angle may be 30, 45, 60, or 90 degrees. Thus, in an embodiment, each “layer” includes at least two sheets of parallel strips (although more sheets may be included without departing from scope hereof). The stacked configuration produces a layer with holes 158 and ridges with valleys, the ridges formed of strips with the valleys formed by space between parallel strips, a bottom of the valley corresponding to a surface of a sheet of an adjacent layer. The holes 158, 160 are formed where gaps between strips of one sheet align with gaps between strips of an adjacent sheet within a given layer, or adjacent sheets of adjacent layers. The strips of the first sheet of a layer are, in embodiments, attached to strips of the second sheet of the same layer with an attachment technique suited to the material of which the layer is made. In embodiments, this attachment technique may be spot welding for metal strips, heat sealing for thermoplastic strips, sewing for some fibrous materials, or an adhesive, selected as appropriate for the material. In embodiments, attachment technique of the first parallel strips 150 of the first sheet of a layer to the second parallel strips 152 of the second sheet of the same layer comprises attaching the strips of respective sheets to each other at a plurality of overlapping areas 153, along an outer periphery 155 of the muffler 100, 200, for example, with a frame, or in any other suitable manner selected for a particular application and / or characteristics of the strips.

[0045] In an alternative embodiment, parallel strips oriented in a first direction are positioned as warp in a loom, and cross strips are woven as weft under odd-numbered strips oriented in the first direction and over even-numbered strips oriented in the first direction, in a manner similar to weaving cloth, to form a layer resembling a cloth or mat woven from the strips. As with the embodiment of Fig. 1A, the strips are spaced so holes are formed at intersections of strips oriented in the two directions, and the strips oriented at angles to each other may be attached to each other as previously described.

[0046] Two or more such layers are either closely spaced with their holes 158, 160 misaligned so that the layers form a sandwich with the layer spacing forming narrow channels between holes, or a sandwich is formed with two or more adjacent layersAtty Docket No. TUOE.P2015WO / 00679628attached together so the valleys serve as channels between holes of the misaligned sheets. Any suitable attachment technique may be used depending on the material, such as spot welding, heat sealing, sewing, weaving, or an adhesive. In embodiments where the layers are spaced apart, one or more spacers such as a spacer layer 165 (Fig. 1C) or plurality of strips, is positioned between layers of the sandwich. In embodiments where the valley formed from gaps between strips is of a thickness desired for narrow channels between holes, or where one or more spacers such as a spacer layer is used, each layer may have the same orientation as shown in Fig. 1C; in embodiments, layers may be oriented with strips at angles to each other that are different from 0 or 90 degrees, or otherwise not parallel, so long as most and preferably all of the holes in each sheet or layer are not aligned with those of adjacent sheets or layers thereby ensuring that there are few, if any, direct paths for sound from one side of the muffler to another side of the muffler.

[0047] In an embodiment, illustrated in Fig. ID, where thickness 180T of the channels between holes is equal to twice a thickness 182T of the strips of which each layer is made. In the embodiment of Fig. ID, a first layer 184 includes sheets 150 and 152, and a second layer 186 includes sheets 154 and 156. Each sheet 150, 152, 154 and 156 includes a plurality of parallel strips as discussed above. The second layer 186 may be inverted and strips of one direction in each layer aligned (e.g., strips of sheets 152 and 154 aligned together), with strips of a second direction not aligned (e.g., strips of sheets 150 and 156 not aligned) as shown in Fig. ID. In such an embodiment the strips of the second layer oriented in the first direction may be fused to, or fabricated as a single thick strip 163 with, the strips of the first layer oriented in the first direction, as shown in Fig. IE. In other words, sheet 152 of first layer 184 and sheet 154 of second layer 186 are integrated into a single sheet of a plurality of strips 163, and the multiple-parallel-strip sheets of the muffler includes three (or more) sheets of parallel strips.

[0048] The net structure formed as described with reference to Figs. 1A-1E is a material sandwich having multiple, narrow, passages from a first side to a second side of the sandwich. This sandwich serves as a muffler 100, 200.

[0049] In an alternative embodiment, the parallel strips are woven to form each layer. In some alternative embodiments, a sandwich is positioned ahead of a back cavity.

[0050] Exemplary muffler 100, 200, has an optional back cavity or chamber 110 behind two layers 118, 124 as described with reference to Fig. IF. Fig. 2 shows muffler 200 with a back cavity or chamber 110 with a domed shape (compared to the flat shape of Fig. IF). Other exemplary embodiments may include more than twoAtty Docket No. TUOE.P2015WO / 00679628sheets / layers, such as 3 or more sheets / layers; embodiments with more than two sheets may have same or different channel widths and / or layer spacings as dictated by performance requirements. Exemplary mufflers according to the disclosure can include any suitable number and / or combination of sheets / layers described herein.

[0051] Bottom layer 118 has holes 120 between a back chamber (if present) or the environment into a space 122 that may be provided between bottom layer 118 and top layer 124, or the layers can be stacked directly on top of each other and the sound can propagate in the channels formed by the gaps between the strips of each layer. Over space 122 is top layer 124 having holes 126 spanning from space 122 to environment 114. In some, but not all, embodiments, airflow through holes 120, 126 is blocked by a thin acoustic membrane 130. Membrane 130 is shown above top layer 124, but it may be located in other positions, such as but not limited to below bottom layer 118, above the bottom layer 118, between bottom layer 118 and top layer 124, and below top layer 124, or a combination thereof if there are multiple membranes 130.

[0052] Acoustic membrane 130, if present, is formed of a flexible material that passes sound, such as thin layers of deformable and bendable polymers, plastics, biobased plastics or metallic films and / or foils. Some suitable examples for materials of the acoustic membrane include acoustic diaphragm and drum materials such as laminates, plastic, aramid fiber such as Kevlar, polypropylene, polyethylene, polycarbonate, glass fiber, carbon fiber, and others. In embodiments the acoustic membrane is supported by other layers of the muffler.

[0053] Back cavity or chamber 110 is an enclosure configured to prevent a shortcut connection between the fluid, whether the fluid be air, water, oil or another material, and the environment, so that the fluid does not pass directly from an outer surface of layer 124 to an outer surface of layer 118 without passing through space 122 between the layers 124 and 118, or through narrow channels as formed along gaps between strips of fused layers as illustrated in Figs. ID or IE. A back cavity is essentially a void volume, sealed walls of which may be composed of, or include, acoustically rigid material. Exemplary embodiments have a back cavity 110 with a depth 112 between a surface of the layer adjacent to the back cavity and a wall of the back cavity facing the layer adjacent to the back cavity of 50 mm or less. A larger back cavity enhances absorption across all frequencies, including ultra-low and low frequencies in the range of 50 mm to 300 mm. However, in most applications, such thicknesses or volumes are not desirable. Therefore, many embodiments use the muffler with the lowest possible backAtty Docket No. TUOE.P2015WO / 00679628cavity — ranging from as small as 1 mm, 2 mm, 5 mm, and 10 mm up to 50 mm — that can achieve significantly better low-frequency absorption compared to traditional acoustic materials of similar total size or volume. Advantageously, the embodiments herein have been shown to achieve at least 10 times greater absorption than the best conventional acoustic materials, such as foams and wools, at specific low frequencies. This is illustrated in Figs. 3A-B.To implement an acoustic tape embodying the muffler described with reference to Figs. 1A-1F and Fig. 2, all elements of the muffler 100, 200, including the top and bottom layers 124 and 118, any additional layers, spacer layer(s), the acoustic membrane 130, and / or the back cavity 110, may be bendable or flexible, for example, due to being made from or including flexible materials such as many plastics, thin fiber-reinforced plastics, fiber materials bonded with flexible resins, thin metal sheets, or textiles.

[0054] Figs. 4A-B show example bendable / flexible embodiments of mufflers described herein. The back cavity 410 of an acoustic tape can be created by adding a bottom layer 412 with one or more and preferably a plurality of projections 414 extending in the direction of the stack 420 of first and second sheets (or layers) 424, 428 and an optional spacer 437 of the muffler 400, as illustrated in Fig. 4A. Sheets / layers 424 are an example of layers 184, 186 and / or sheets 150, 152, 154, 156 discussed above, and the description thereof applies and the description of each applies to each other unless otherwise specified. Back cavity 410 is an example of back cavity 110 discussed above and the description of each applies to each other unless otherwise specified.

[0055] In these embodiments, a thin acoustic membrane 430 transparent to sound but capable of blocking mass airflow may optionally be provided as part of, or adhered to, the muffler sandwich. Thin acoustic membrane 430 is an example of acoustic membrane 130 discussed above and the description of each applies to each other unless otherwise specified. In embodiments, one or more projections 414 are in contact with a side of the stack 420 that faces the back cavity 410. One example of a bottom layer 412 formed with at least some strips having a plurality of projections 414 as dimples formed by dome-shaped indentations, the indentations serving as projections. In other exemplary embodiments, the bottom layer 412 is a sheet having a plurality of projections 414 as dimples formed by dome-shaped indentations, the indentations serving as projections. However, many other types of projections are possible, including pyramidal, rod-shaped, wave-shaped, and other projections. Such constructions allow the forming of a small back cavity that does not collapse when the acoustic tape embodying the muffler is bent, curvedAtty Docket No. TUOE.P2015WO / 00679628or wound fully or partially about a core. In exemplary embodiments of acoustic tapes, the depth of such a back cavity, defined as a maximum distance between the layer 412 and the stack 420 of layers 424, 428 can range from 0.5 to 5 mm. Such exemplary embodiments find application, for example, as acoustic wallpaper.

[0056] An adhesive layer, and optionally a release liner, may further be included in an acoustic tape for attaching the muffler 100, 200, 400, to other objects. One or more adhesive layers can also be provided on surfaces of one or more layers and / or one or more spacer layers, such as a spacer layer provided between the first and second layers. Exemplary acoustic tapes described above have the advantage of being suitable for attachment or otherwise fitted to or around curved surfaces. Another advantage of such embodiments is that they can be provided in the form of a roll, as shown in Fig. 4B. For example, a roll of acoustic tape can include a core 431, and an exemplary flexible muffler / acoustic tape 435 wound on the core. In other exemplary embodiments, a core 431 can be any desired article that can benefit from a noise reducing acoustic tape application.

[0057] Fig. 2B is an exploded view of an embodiment of an acoustic assembly including a back cavity or chamber 2010 positioned posterior to a muffler 2000. Back cavity 2010 is an example of back cavity 110 discussed above and the description of each applies to each other unless otherwise specified. The exemplary back cavity 2010 optionally has an overall uniform depth D, for example between 4 cm and 6 cm, and is internally subdivided into two, three, four or more partitioned cavity sections, such as 2020a, 2020b, 2020c, 2020d. While the illustrated embodiment of the back cavity 2010 includes 12 cavity sections, other numbers of cavity sections are within the scope of the disclosure. At least two, three, or more, of the cavity sections have different dimensions resulting in two, three or more different volumes VI, V2, V3, etc. of the cavity sections. Differences in these volumes allow each cavity section to be tuned to a distinct target resonance frequency. For example, in one embodiment, the system may include: a first cavity section 2020a having a first volume tuned to a first target resonance frequency, a second cavity section 2020b having a second volume tuned to a second target resonance frequency, and, optionally, a third cavity section 2020c having a third volume tuned to a third target resonance frequency, and / or a fourth cavity section 2020d tuned to a further selected frequency. The first, second, third, fourth, and other additional target resonant frequencies to which the cavity section volumes may be advantageously tuned may include 200 Hz, 400 Hz, 1,300 Hz and / or other frequency of interest.Atty Docket No. TUOE.P2015WO / 00679628

[0058] The cavity sections can be formed by one or more internal partition walls 2030a, 2030b, 2030c, 2030d extending substantially orthogonally toward the rear surface of the muffler 2000 (e.g., the bottom surface of muffler 2000 in Fig. 2B; when the muffler 2000 is assembled with the back cavity 2010) from a rear wall 2040 of the back cavity 2010. Muffler 2000 may include any of the features discussed above with respect to mufflers 100 or 200 without departing from the scope hereof. In such embodiments, two, three, four, or more or more cavity sections 2020a, 2020b, 2020c, 2020d with different volumes are formed by the one or more partition walls 2030a, 2030b, 2030c, 203 Od. One or more partition walls may share the same cavity depth D but are placed such that the cavity sections differ in one or more lateral dimensions, such as a width and / or length, resulting in different effective acoustic volumes.

[0059] In one illustrative arrangement, the back cavity 2010 is divided into cavity sections by two generally parallel partition walls extending along a first direction and, optionally also two, three, or more generally parallel walls extending along a different direction. A larger cavity volume (Vi) may be positioned adjacent to a smaller cavity volume (V2), with a further larger cavity volume (V3) adjacent to the smaller cavity volume (V2), creating a distributed set of acoustic chambers optimized for broadband absorption within the limited overall depth D.

[0060] When cavity sections 2020a-2020d are arranged adjacent to one another within the single back cavity structure 2010 and assembled with a muffler 2000, the combined assembly achieves broadband acoustic absorption performance. In certain embodiments, each cavity section may exhibit absorption coefficients approaching 90% at its respective tuned frequency, producing broadband absorption without requiring modification of the muffler 2000, which makes the muffler assembly more versatile and easier to manufacture.

[0061] The layer patterns of Fig. 1A-1E can also be used to create soundproof clothing or sonic curtains; in cloth embodiments, layers may be glued together including any number of sheets in each layer and may further include an acoustic membrane.

[0062] The holes 120, 126 in the bottom and top layers, respectively, may have a variety of shapes, including holes, grooves, slits, rounded slits, squares, rounded squares, triangles, rounded triangles, pentagons, rounded pentagons, hexagons, rounded pentagons or a combination thereof. The shape and / or size of holes 120 in the bottom layer and of the holes 126 in the top layer may be the same or different. In some embodiments, size of the holes ranges from 0.001 mm to 5, 7, 15 mm or more. In someAtty Docket No. TUOE.P2015WO / 00679628embodiments, the holes of one or both layers 118, 124 are arranged in a regular pattern. In such embodiments, the arrangement of holes can be characterized by a pitch dependent on strip width.

[0063] The spacing between top layer and bottom layer, or the channel width in embodiments where the channels are formed by the valleys between strips, is small enough that thermo-viscous boundary layer effects have a significant impact upon the propagation of sound along the narrow, rigid-walled channel formed between holes of the top layer and bottom layer giving substantial acoustic attenuation within the audio frequency range. This attenuation is a function of 8S / W where 6S= 2n j2v / (j) is Stokes's boundary layer thickness, and v is kinematic viscosity defined as the ratio of the dynamic viscosity (p) over the density (p) of air, water, or another fluid of interest, and IV is the channel width or the layer-to-layer distance 128. Viscosity (p) is a function of pressure and temperature, which change with altitude. With rigid-walled channels with widths on the order of Stokes's boundary layer thickness, the attenuation in air can be over 6.86 dB / wavelength; for the channel width of half stokes boundary layer, = 2, would be 16dB / wavelength and for the channel width of twice of the stokes boundary layer,= 0.5,would be 3 dB / wavelength.

[0064] The Stokes's boundary layer thickness for frequency range of 20 Hz to 20kHz would be between 0.09 mm and 3 mm. For instance, at 4000 Hz, (wavelength 343 / 4000=0.086 m), by selecting a channel width on the order of Stokes’s boundary layerthickness ( > = 0.21 mm), the muffler can have 6.86dB / wavelength means 6.86 / 0.086=80 dB / m attenuation. This number for the case of channel width of half stokes boundary layer,= 2, would be 16 / 0.086=186 dB / m andfor the channel width of twice of the stokes boundary layer,= 0.5, would be 3 / 0.086=34 dB / m. Therefore, shorter sizes of the gap or channels have higher attenuation but also have higher resistance for passing the airflow.

[0065] The Stokes boundary layer thickness varies with types of fluid, or media, through which sound propagates within the gap between layers 118, 124 (or in channels formed by strip-to-strip spacing or in channels of spacer layers that separate layers of spacer-layer embodiments) and in holes 120, 126 of layers of the muffler. Example Stokes boundary layer thicknesses are found in table 1 below, Stokes boundaryAtty Docket No. TUOE.P2015WO / 00679628layer thickness can be computed for other materials, such as oils, for specific applications. In the table, VIS is kinematic viscosity in M2 / sec, Stokes size is thickness of Stokes boundary layers in millimeters,Table 1, Stokes boundary layer thickness of Air (at 20°C and 1 atm) and Water (at 20°C and 2,3kPa) at various frequencies.

[0066] In a particular embodiment, the distance 128 between top layer 124 and layer 118, or channel dimensions in other embodiments, is no more than twice the Stokes boundary layer thickness estimated at a frequency needing attenuation. The frequencies needing attenuations are dependent on the application of the muffler, but typically range from 100 to 400 Hz for wind turbines, heat pumps, from 20 to 100 Hz for aircraft, and 400 to 3000 for other vehicles, construction machineries, and construction buildings.

[0067] Narrowness of the channel between the holes of the top and bottom layers, or narrowness of the channels between holes in the layers, is important in function as this forms the damping channel of a broadband ultra-thin muffler that dampens noise at a wide broadband range of frequency. The muffler may work simultaneously from 2 Hz to 8kHz and in some special designs for even higher frequencies (up to 20kHz). In general, it can perform at ultra-low frequencies (2-100 Hz), at low frequencies (100 Hz to 1000 Hz), and mid frequencies (1000 Hz to 2000 Hz), and higher frequencies (above 2000 Hz). The muffler has been designed, built, and verified by analytic solution and numeric simulation via commercial software and verified by laboratory testing.Atty Docket No. TUOE.P2015WO / 00679628

[0068] The measured reflection coefficient of the muffler even at ultra-low frequencies is less than 0.05, meaning 99.99% of the acoustic energy is either absorbed or transmitted from the muffler and nearly nothing is reflected back. The muffler can have a thickness of a few millimeters based on the applications. Because of the ultra-thin size of the muffler, it can be easily integrated, for example as an acoustic tape, to other noise reduction systems.

[0069] Depending on application requirements, hole counts, and hole sizes, the gap between top layer and bottom layer, or the thickness of channels formed by the valleys, of some embodiments, is chosen to be between 0.001 and 2 millimeters, inclusive, or between 0.05 and 1.5 millimeters, inclusive, and in some cases 0.3, 0.25, 0.22, 0.2, 0.15, 0.1 or, 0.07 millimeters as given above. In an embodiment, the holes of the top layer are shifted relative to the bottom layer such that the majority of the holes of the top layer are not directly aligned with the holes of the bottom layer. In other embodiments, none of the holes of the top layer align directly with holes of the bottom layer.

[0070] The space 122 may be created using spacers or a spacer layer disposed between the layers. Examples include a mesh, one or more wires, wedges, rings and / or strips. It could also be a perforated sheet with thickness similar to the needed gap size and with larger opening areas than the holes in the top layer and the bottom layer such that the holes connect the misaligned top and bottom layer opening areas to each other. In one embodiment, a spacer layer is provided between the second and first layer, which spacer layer includes multiple openings or slits. The openings in the spacer layer can have any suitable shape, such as circular, elliptical, square, rectangular, L-shaped, S-shaped, or a combination thereof. In exemplary embodiments, the openings of the spacer layer couple at least two non-overlapping holes of the second and first layers 118, 124. Optionally, the space 122 may contain absorbing or porous material(s), metal foam, and / or fiber.

[0071] As mentioned before, for most of the configurations which are under discussion here, the channel width (spacer gap) is smaller than twice the Stokes boundary layer thickness of a frequency of interest.

[0072] In particular embodiments, the strips of the mufflers discussed herein may range in thickness from 0.01 mm to 5 mm, and in some embodiments from 0.05 mm to 2 mm thick. Strip width in embodiments may range from 1 mm to 50 mm, from 1 mm to 35 mm, and in some particular embodiments from 6 mm, 12 mm, 25 mm, or 35 mm. Gaps between strips in a sheet in embodiments may range from 0.5 mm to 25 mm, and in particular embodiments from 0.5 mm to 15 mm, 1 mm to 8 mm, or from 3 mm to 8 mm.Atty Docket No. TUOE.P2015WO / 00679628We note that strip thickness and width, and gap, dimensions may affect channel width, and, for maximum effectiveness at frequencies of interest, channel width should be less than twice the Stokes boundary layer thickness at frequencies of interest as previously discussed.Muffler Applications

[0073] Embodiments of the ultra-low frequency broadband ultra-thin muffler discussed herein (e.g., any one of muffler 100, 200, 400, 2000 discussed above) are useful at a broadband range of frequencies. The muffler may work simultaneously from 2 Hz until 2kHz and in some exemplary embodiments for even higher frequencies (up to 20kHz). The muffler may also be tuned to work at a specific region of frequencies associated with particular applications, and multiple mufflers having different design parameters can be stacked to gain even broader frequency response.

[0074] The muffler may have a thickness of some microns to some centimeters and the other sizes (length and width of the muffler) may be on order of microns to hundreds of meters as needed for the wind turbine application discussed below. Because of the ultra-thin size of the muffler, it may be easily integrated to any kind of geometries that generate noise. The performance of the muffler may reach up to and more than 99% of energy being damped. The measured reflection coefficient of exemplary mufflers even at ultra-low frequencies is less than 0.05 which means 99.99% of the acoustic energy is either absorbed or transmitted from the muffler and actually almost nothing is reflected back.Wind Turbine Blade Applications

[0075] Blade tip velocities of typical wind turbines may exceed 8 times the wind velocities the wind turbine is exposed to, thus reaching tip speeds of hundreds of miles per hour in light to moderate winds, while many wind turbines vary blade pitch to reduce tip-to-wind speed ratios at moderate to high wind speeds, high blade-tip velocities can still be expected. Blade tips at such high velocities can cause significant noise.

[0076] A common blade configuration 50, in this example a wind turbine blade of length about 50 meters and NACA 0018 airfoil, is illustrated in Fig. 5. As blade tips generate much of wind-turbine noise, a muffler 500 was simulated as used on a portion of the blade near the tip 52 as shown in Fig. 5. Muffler 500 may include any of the features discussed above with respect to mufflers 100, 200, 400, and / or 2000. While simulations focused on the portion near the tip, the muffler may be applied anywhere along the wall 54 of the blade 50.Atty Docket No. TUOE.P2015WO / 00679628

[0077] Near the blade tip 52, the blade airfoil was simulated with a portion along the trailing (downwind) edge 55 of the blade 50 formed according to our two-layer muffler 500 (e.g., similar to those discussed above with regards to Figs. 1B-E) with closely-spaced top and bottom layers including, in an example, 2 mm holes distancing 6 mm from one another. The top layer is shifted from the bottom layer by, in this example 2 mm, so that the air acoustic wave is compelled to follow a tortuous path as it passes through these two layers having holes defined by gaps between strips (narrow channel). Inside the exemplary blade 50 further illustrated in Fig. 6 is a void 56 and air is trapped in this internal volume cavity. The void 56 serves as a back cavity or chamber of this exemplary embodiment and the muffler 500 is incorporated into the blade wall 54 such that it separates the void 56 within the blade 50 from external environment. Thickness of the blade wall 54 of this example is 1cm and this stems from the void or back cavity 56 volume V to the total area of the openings of the muffler A (number of holes times area of the holes) part fraction. In this context V / A should be more than 5 for ultra-low frequencies (blow 100Hz) to achieve a 99% absorption, where V and A denote back cavity volume and muffler opening area, respectively.

[0078] Adding the muffler at the trailing edge 58a of the blade 50 can reduce the maximum Sound Pressure Level area from that generated by an unmodified airfoil at 100 Hz significantly.

[0079] Further reductions in sound pressure levels can be achieved by adding the muffler at both upwind 58a and downwind 58b edges. In an embodiment, a muffler according to the present disclosure is located in a region of the blade or airfoil that is closest to the acoustic source and / or on the suction side of the blade. A plurality of mufflers according to the present disclosure may be incorporated in a wall 54 of a blade or airfoil 50 at locations where the acoustic field has the maximum absolute value of the acoustic pressure. In one implementation, a muffler according to the present disclosure may span a substantial portion of the surface of the blade or airfoil 50, extending beyond the blade tip 52. In embodiments, these mufflers have an acoustic membrane across their surface to prevent disruption of airflow. The membrane can be disposed over the outer surface of the muffler and / or another location as described above. While the description above specifically mentions a blade of a wind turbine, drone blades, fan blades, helicopter blades and other airfoils having the general configuration as described above and shown in Figs. 5 and 6 can be designed to incorporate mufflers according to the present disclosure.Atty Docket No. TUOE.P2015WO / 00679628

[0080] In some embodiments, such as axial fans 700, 700a illustrated in Fig.7, there is often no void inside the blade and an exemplary muffler 770, 770a is incorporated, e.g., laminated or otherwise integrated, into one or more of the fan blades 750, 750a. In an embodiment, a fan 700, 700a is configured such that a muffler 770, 770a is integrated into multiple or all blades of the fan. One or more of the blades 750, 750a configured in this manner could include a muffler 770, 770a having openings on both sides connected by the narrow channels as described above or a muffler comprising an acoustic membrane. In other exemplary embodiments, where a muffler is laminated onto one or more standard blades, the muffler can have a construction including a back cavity as described herein. Mufflers 770 or 770a may include any of the features described above, e.g., with respect to mufflers 100, 200, 400, 2000, without departing from the scope hereof.

[0081] Another application for mufflers according to the present disclosure, particularly, with a surface covered with an acoustic membrane, is hoods and other exterior and interior surfaces of motor vehicles, where it is desirable to dampen both engine noises, tire noises, and airflow noises. Another example is absorbing aeroacoustics noise of an automobiles or trucks. The example illustrated in Fig. 8A is a hood 82 of a moving vehicle 80 (or another outer part of a body of any moving device). It is possible to consider the internal volume of the engine side of the vehicle 80 as a back cavity because it has a different acoustic pressure respect to the air surrounding the vehicle. Therefore, by applying a muffler 800 to the hood 82, a connection between surrounding air and the air inside the engine part is prepared and the closest way to connect these two fluids is passing through the muffler which causes noise reduction. The muffler in these vehicle applications is usually covered by an acoustic membrane so there are no rough edges to provoke vortexes on the surface and allowing a smooth paintable surface. Figure 8A shows a vehicle with a muffler 800 incorporated in its hood 82 and in rear tire covers 84.

[0082] Additionally or alternatively, mufflers according to the present disclosure may be incorporated into doors or other external and / or internal surfaces of vehicles. Fig. 8B depicts a muffler according to the present disclosure incorporated into a door panel, in embodiments. In such embodiments, a muffler 800a can be integrated into an interior side of a body panel 86 of the vehicle 80, such as a door panel. In this case as well, the internal volume of the panel 86 disposed between the inner and outer sides of the body panel 86 serves as a back cavity, because it has a different acousticAtty Docket No. TUOE.P2015WO / 00679628pressure respect to the air within the vehicle. Therefore, by applying a muffler 800 to the interior side of the vehicle panel 86, a fluidic connection is formed between the interior of the vehicle and the interior volume of the panel and the closest way to connect these two fluids is passing through the muffler which causes noise reduction.

[0083] Vehicles in which the mufflers according to the present disclosure may be used include, without limitation, helicopters, airplanes, drones, construction equipment, rotary machines, cars, and trucks. In general, mufflers according to the present disclosures can be incorporated in fixed parts and parts that move at the speed of 1 m per second or more. When made from electrically conductive materials, it can also be used to reduce electromagnetic noise and shield from electromagnetic pulse or other electromagnetic interference, such as when the muffler is arranged to high-voltage electricity cables or electronic boards, as well as dampening fan noises of computers, laptops, and other electronic equipment. Additionally, it can be used as a casing for motors in drones, fans, and industrial electro-motors, effectively reducing operational noise. Specifically for drones, the muffler’s ultra-thin, lightweight, and highly absorbent properties make it an excellent solution for covering drone motors, minimizing noise without adding excessive weight or affecting performance. The holes in the mufflers allow heat to dissipate, preventing any significant temperature increase inside the muffler.Parallel strip muffler with overlapping strips.

[0084] A muffler may be constructed of overlapping parallel strips or slats 1102 of material as illustrated in the lateral view of Fig. 11A and the top view of Fig.1 IB. In this muffler, spacers 1104 are provided such that there are narrow channels 1106 forming a passageway for sound between airspace of a first side 1108 and a second side 1110 of the muffler, the narrow channels 1106 extending along an overlap area between each pair of strips or slats except where the channel is filled by spacers 1104. The overlap area relative to the total width of strips or slats is determined according to muffler performance requirements, and the thickness of spacers is determined to be less than the double Stokes boundary layer thickness of a frequency of interest where good attenuation is desired. The airspace of the second side 1110 may be a back chamber (which is an embodiment of other back chambers discussed herein, such as back cavity 110), and an acoustic membrane may be applied along either side of the muffler as appropriate for the application.

[0085] In a particular, switchable, embodiment, the strips or slats of the muffler shown in Fig. 11 A and 1 IB are pivotably mounted and coupled through gearing, a chain,Atty Docket No. TUOE.P2015WO / 00679628or a belt to provide rotation to the strips or slats to permit them being rotated from a muffling mode as shown in Fig. 11 A to a non-attenuating mode as shown the lateral view of Fig. 11C. Such switchable mufflers may be of use to permit vehicles to meet noise ordinances while in towns while entertaining crowds with thunderous noise at dragstrips or hill-climb events. They can also be constructed as window shades for use in residences, where the non-attenuating mode permits both sound and light to pass through during daytime, while blocking light and noise at night while residents are sleeping.

[0086] Fig. 11D shows schematically a cross section of another exemplary embodiment of a muffler assembly including parallel strips or slats 1102, where the mufflers according to the disclosure, such as 100, 200, 400 illustrated in Fig. 1A-F, 2A-B, and 4A-B are incorporated into the slats or strips 1102. As such, the discussion of mufflers 100, 200, 2000, and / or 400 discussed above is incorporated by reference here and applies to Fig. 11D. In such embodiments, a plurality of slats or strips are mounted at one or both longitudinal ends, fixedly or pivotably, onto a frame (not shown). The mufflers according to the disclosure, e.g., 100, 200, 2000, and / or 400 may form the strips or slats 1102 and / or the mufflers may be disposed on one or both surfaces of the slats 1102. In embodiments, one or more slats 1102 may include, as a part of their construction, a honeycomb structure, preferably a generally planar honeycomb structure, with a muffler according to the disclosure attached or otherwise provided on one or two sides of the honeycomb structure. At least part of a periphery of the honeycomb structure that is not covered by a muffler may be open to the atmosphere. In an embodiment, one side of the periphery of one or more slats including a honeycomb structure and a muffler according to the disclosure on one or two sides of the honeycomb structure is open to the atmosphere. Another side of the periphery may be closed. In other exemplary embodiments, the interior of one or more slats may be hollow, empty, or filled. A plurality of slats 1102 according to the disclosure may be used in acoustic grills and / or ventilation louvers.

[0087] Fig. 12 is a view of a wall hanging or artwork implementation of the muffler described herein with a back chamber having a low-density sound absorbing material to broaden frequency response. Back cavity configurations illustrated and described in reference to Fig. 2B (or other back cavities discussed herein) are also suitable for use in this implementation. In this embodiment, artwork may be either printed directly on the crossed strips of a muffler 1204 as described with reference to Figs. 1A-1F, the strips or slats of a muffler as described with reference to Fig. 11, or on an acousticAtty Docket No. TUOE.P2015WO / 00679628membrane 1202 positioned directly on, or spaced close to, a room side of the muffler 1204. Sound to be attenuated passes through acoustic membrane 1202 if present to impinge on muffler 1204 and is dampened as it passes through narrow channels 1205 of muffler 1204 as previously described. A frame 1206 supports the muffler. A back cavity 1208 may be provided in some embodiments, particularly those for which high nose absorption is desired. Sound absorption of an embodiment of the muffler of Fig. 12 having multiple, very small, holes drilled in each strip is illustrated in Fig. 15B showing a much flatter frequency response than the response of an unfilled muffler illustrated by the AIR curve in Fig. 13.

[0088] In some, but not all, embodiments of the muffler of Fig. 12, the back chamber or back cavity 1208 may contain an optional lightweight sound absorber 1212 configured to absorb high frequency sounds. While the sound absorber 1212 degrades peak performance at low frequencies where the narrow channels of the muffler 1204 have dimensions less than twice the Stokes boundary layer thickness and thus most efficiently absorbs sound, use of sound absorber 1212 helps absorb high frequency sounds where the Stokes boundary layer thickness is less than at the lower frequencies. This effect can be used to give a flatter and broader frequency response than available with a single, empty, back chamber.

[0089] As an alternative to the sound absorber 1212, two mufflers of Fig. 1A-1F with different passage dimensions, one for high frequencies and one for lower frequencies, may be used in series as muffler 1204.

[0090] In some exemplary embodiments, the back cavity 1208 of an acoustic panel illustrated in Fig. 12 may include or be formed from a honeycomb structure, e.g., a generally planar honeycomb structure. A muffler according to the disclosure may be attached or otherwise provided on one or two sides of the honeycomb structure. An acoustic panel may be configured such that at least part of a periphery of the honeycomb structure that is not covered by a muffler may be open to the atmosphere. In an embodiment, one side of the periphery of an acoustic panel including a honeycomb structure and a muffler according to the disclosure on one or two sides of the honeycomb structure is open to the atmosphere. Another side of the periphery may be closed. In other exemplary embodiments, the back cavity of the acoustic panel may be hollow or empty. A plurality of acoustic panels according to this and other embodiments of the disclosure may be provided side by side in a spaced apart arrangement, for example, hung from aAtty Docket No. TUOE.P2015WO / 00679628ceiling or from another support structure. In such configurations acoustic panels of the present disclosure may serve as acoustic baffles.

[0091] While back cavity 1208 increases effectiveness of the muffler, and is most economically produced with air at the same pressure as air in the room in which the muffler system is hung, it also requires a minimum thickness for best results particularly at low frequencies where wavelengths are long. This thickness for a desired frequency performance can be reduced either by lowering air pressure in the back cavity 1208 or filling the back cavity with a gas having high molecular weight. In a particular embodiment, an impermeable acoustic membrane is formed as part of muffler 1204 or used as printed membrane 1202 and either a partial vacuum is present in back cavity 1208 or a high molecular weight gas such as butane or Xenon is used to fill back cavity 1208. Fig. 13 illustrates simulated frequency dependence of a muffler having a fixed back cavity of 55 mm with various molecular weights of gas fill showing that high molecular weight gas reduces frequency peaks and thus can reduce required back cavity depth. Similarly, Fig. 15A illustrates frequency dependence from 50Hz to 1kHz of absorption of a muffler having a fixed back cavity of 55 mm with various air pressures.Shapes other than Straight Strips

[0092] Each sheet of a layer of a muffler may be formed of strips of material that are not straight, albeit having edges that are largely parallel and spaced apart so that holes are formed at intersections of valleys formed by gaps between the strips. The embodiment of a layer illustrated in Fig. 16 is constructed of two sheets zig-zag “strips” having multiple 90-degree bends in each strip. It should be appreciated that angles other than 90-degree, including acute or obtuse angles, may be implemented without departing from the scope hereof. The lower sheet is inverted with respect to the top sheet so that the gaps between strips of the lower sheet intersect gaps between strips of the top sheet to make holes. Two such layers may be closely spaced, but spaced apart, with a spacer layer and with holes misaligned to form a muffler that works, as described herein, by forcing sound to pass through a multiplicity of narrow channels formed by gaps between shapes of a sheet and / or a narrow gap between layers.

[0093] The muffler designs herein described may be expanded to include layers formed of other arrangements of gapped shapes in each sheet, where the gaps between shapes of a first sheet of each layer cross gaps of shapes of a second sheet of the same layer to form holes, and where additional sheets or an additional layer is positioned toAtty Docket No. TUOE.P2015WO / 00679628form narrow channels for sound to pass from one side of the muffler to an opposite side of the muffler.Silent body Applications

[0094] To create silent bodies or acoustic walls, such as the rigid casing of devices or separator walls in units, one approach is to reinforce mufflers according to the present disclosure with stronger materials like metal, plastic, or bio-based materials. Another possibility is to use a porous material and attach the muffler according to the present disclosure, such as those of Figs. 1A-E, to one side or both sides of the wall. In this configuration, the wall blocks mass flow while the back side serves as a back cavity, e.g., back cavity 110 shown in Fig. IF or back cavity 1208 shown in Fig. 12, enhancing the absorption properties of the muffler. Although the proposed muffler has a higher transmission coefficient than rigid materials, by incorporating acoustic membranes and narrowing the gaps, we have achieved up to 35 dB Transmission Loss, meaning less than 1% of the acoustic pressure is transmitted through the acoustic wall, while 50 to 99% of the sound energy is absorbed by the wall or silent body. This application has a huge impact on eliminating plastic materials, such as ABS and EPP, in the production of devices and units. Our muffler provides similar structural strength to the rigid plastic walls or casings currently used while eliminating the need for injection moulding and other complex manufacturing processes. Furthermore, since the acoustic wall is produced in layers, it can be easily shaped into curvatures or 3D forms, which is currently not feasible with traditional injection molding techniques.Silent Concrete walls

[0095] This concept can also be extended to concrete walls. In this application, we develop porous concrete with open cells, and then apply acoustic tape on one or both sides of the wall. This exemplary embodiment 1700 is illustrated in Fig. 17. The muffler according to the present disclosure, for example, shown in Figs. 1A-E, 16, or any of the mufflers discussed herein, can be attached to a first surface 1702 of a mass of open cell porous concrete 1710, which may be in the form of a concrete slab or any other suitable shape. The second surface 1704 of the concrete mass 1700 may be attached to other structural elements. However, in some embodiments, a muffler according to the present disclosure may be disposed on both the first and second surfaces 1702 and 1704. In some embodiments the first surface may be disposed opposite the second surface. The muffler can be made from the same or similar material (e.g., cement) to seamlessly integrate with the wall, resulting in silent concrete with significantly improved sound absorption. ThisAtty Docket No. TUOE.P2015WO / 00679628application has a significant impact on building construction, as it eliminates the need for additional acoustic panels, carpets, or other noise-absorbing materials, preventing echo effects in concrete buildings. Additionally, it removes the necessity of incorporating acoustic materials inside separator walls between rooms, allowing for a reduction in wall thickness without compromising acoustic performance. The porosity of the concrete plays a crucial role, as it functions as the back cavity of the muffler, enhancing sound absorption. Moreover, increased porosity reduces the overall weight of the concrete, contributing to more efficient material use. However, careful optimization is required to maintain the structural strength of the concrete, ensuring it meets both acoustic and loadbearing requirements.

[0096] In an alternative embodiment, a muffler assembly 1700 can be implemented by providing a plurality of narrow channels 1740 in the first surface 1702 of the concrete mass 1710. In such exemplary embodiments, the concrete may include a plurality of open or closed pores 1740 or it may be non-porous. The length of the narrow channels 1740 is typically at least 5 mm and preferably from 5 mm to 50 mm. Average distance between the channels is typically at most 50 mm, and preferably from 1 mm to 10 mm. Average size of the openings may be from 0.05 to 2 mm. Open area ratio (total area of holes divided by the total area of the surface in which the holes are provided) should be 10% or more, and preferably 30 to 60%.Sonic curtains

[0097] Another promising application of mufflers according to the disclosure (for example, those illustrated and described in reference to Fig. IB or 16, or other embodiments described herein) is in sonic curtains. Currently, traditional sonic curtains weigh between 3 to 4 kilograms per square meter and provide a maximum transmission loss of 17 dB. However, the fabric-based muffler developed according to embodiments herein achieves much higher transmission loss and greater absorption, while weighing only 300 to 700 grams per square meter — a significant weight reduction within thickness of 1 to 3mm. This technology is particularly suited for opera halls, theatres, and auditoriums, where aesthetic fabric curtains are preferred while also requiring high-performance noise absorption. Our innovative sonic curtains offer a superior combination of acoustic performance, lightweight design, and visual appeal, making them an ideal solution for such environments.Atty Docket No. TUOE.P2015WO / 00679628ExamplesAcoustic Tape Applications

[0098] Acoustic Tapes incorporating the muffler, such as those discussed with respect to Fig. 4A and 4B or any other embodiments described herein, can be applied to various surfaces or suspended in the air to reduce noise. Increasing the number of layers can improve absorption up to 99%. To maximize absorption performance, multiple sets of mufflers can be arranged with short distances between them, optimizing overall sound absorption. The spacing between each pair of mufflers can range from 1 mm to 5 cm, depending on the desired absorption characteristics. When utilizing materials such as textiles that inherently possess acoustic absorption properties, the absorption percentages may increase even further. For applications involving soft textile materials, such as cotton, polyester, or blends, the layers can be glued, sewn, or stitched together to ensure the holes and micro channels remain securely in place. Moreover, the material should be sufficiently stretched to prevent the layers moving or bending. It's important to stretch the material slightly to prevent the layers from shifting, which could increase the distance between them. If the layers move, it would disrupt the microchannels' functionality, thus reducing the efficiency of the muffler.

[0099] To ensure that fabric or plastic materials cease acting as an acoustic membrane and act as a muffler, some such materials must be stiffened by sewing, gluing, or stitching the layers together, and secured to reduce movement. Typically, thin, flexible materials used in acoustic membranes vibrate easily, allowing sound waves to pass through with minimal absorption and reflection. However, for muffling purposes, the material must be tightly secured and immobilized to prevent this movement and enhance absorption.Acoustic Jacket ApplicationMufflers according to the present disclosure, such as those configured as illustrated in Fig. 1A-1E, may be integrated into an acoustic jacket 900, illustrated in Fig.9A, which may be used to dampen the noise of industrial components or equipment, such as a heat pump, when installed on a compressor or another noise-producing component as shown in Figs. 9B and 9C as a part of an acoustic jacket assembly. As shown in Fig.9A, the acoustic jacket 900 includes at least a body part 902 comprising a muffler according to the present disclosure. The jacket body part 902 is configured to at least partially or fully surround a compressor body 91 or another noise-producing component, such as a magnetic, ball or another valve, an oil, water, or another pump, generators, gas turbines, batteries, electronics rack, etc. The acoustic jacket 900 may further includeAtty Docket No. TUOE.P2015WO / 00679628additional materials, for example, as an extra layer, including rubber, foam, glass wool, mineral wool and / or other suitable materials.

[0100] The acoustic jacket 900 preferably also includes a hat portion 904, and, optionally, a bottom 906 (not shown). The hat portion 904 can be attachable to an upper region of the jacket body 902. The hat portion 904 and / or the bottom 906 may also include a muffler according to the present disclosure, and, optionally, additional materials described above. The jacket is sized and configured to completely or at least partially enclose a noise-producing component such as a compressor 90, such that acoustic leakages are minimized. The acoustic jacket body part 902 may be initially configured as a rectangular sheet (see Fig. 9B) that is (removably) sealed around the compressor or another noise-producing body 90 using a suitable closure, such as a hook and loop closure, tape, or another closure mechanism. The hat portion 904 typically includes one or more openings configured to permit one or more compressor or other pipes 92 to pass therethrough. Accordingly, Fig. 9B shows compressor gas pipes 92 extending through corresponding openings provided in the hat 904. When the jacket is in use, the one or more openings in the hat 904 are sealed around the one or more pipes 92 to prevent leakages, while the jacket body 902 preferably completely surrounds the body 92. In other embodiments, one or more pipes 92 may extend through one or more openings in the hat portion 904, jacket body 902 and / or the bottom potion 906. In such embodiments, the opening(s) comprise flexible material configured to dampen vibrations of the pipe(s) 92. The hat 904 is attached to the jacket body 902 in a sealed manner to prevent acoustic leakages, for example with stitching, hook and loop closure, tape, etc. If the bottom part 906 is present, it is also attached to the acoustic jacket body 902 in a sealed manner. In some embodiments, the compressor system includes a casing 94, in which case, the acoustic jacket 900 is configured to fit within the casing 94. In some exemplary embodiments, the casing itself includes, for example in its interior, a layer comprising a muffler according to any of the embodiments of mufflers of the present disclosure. The terms “top”, “bottom”, “upper” and “lower” are used herein merely in a relative sense and other orientations of the jacket portions described herein are within the scope of the present disclosure.

[0101] It is well known that traditional jackets for noise-producing components, such as rubber compressor jackets, are fastened to the compressor or another noise producing body as tightly as possible to reduce vibrations. This traditional design is based on mass law. However, surprisingly, the present disclosure provides anAtty Docket No. TUOE.P2015WO / 00679628alternative design of an acoustic jacket with a gap between the acoustic jacket body part 902 and the compressor or another noise producing body 92, while managing the noise performance. Accordingly, an exemplary acoustic system according to an embodiment of the present disclosure includes a compressor 90 having a compressor body 91 and an optional casing 94 surrounding the compressor. An acoustic jacket assembly 900 includes a jacket body part 902 comprising a sound dampening material including any of the mufflers discussed herein and / or another sound dampening construction; wherein the jacket body part 902 surrounds the compressor body 91 while being spaced apart from the compressor body 91 over at least a substantial portion of the surface area of the compressor body 91 that is adjacent to the jacket 900. Preferably, the jacket body 902 completely surrounds the compressor body 91 without touching the compressor body 91. The gap between at least a substantial portion of the jacket body 902 and the compressor body 91 should be at least 1 mm to break the vibration transmission path. Such a gap can be created by providing a mesh between the jacket body 902 and the compressor body 91. For example, mesh 908 can be included as an inner layer of the jacket body part 902 as shown in Fig. 9A. In other embodiments, the gap may be created by providing one or more ribs, rings, rails, or a plurality of projections such as ridges and / or dimples on the side of the jacket 900 that faces the compressor 90 or locating other type of spacers or spacer layers between the jacket 900 and the compressor 90.

[0102] The jacket body part 902 is preferably also spaced apart from the compressor casing 94 over at least a substantial portion of the surface area of the casing that is adjacent to the jacket 900. The gap between a substantial portion of the jacket body 902 and the compressor casing 94 should also be at least 1mm, and can be created, for example, as described above.Acoustic Panel Application

[0103] Various configurations of acoustic panels using the muffler configured as illustrated in Fig. 1A-1E are feasible. Impedance tube tests indicate that these panels can achieve Class A acoustic panel status, with significantly higher absorption than standard Class A panels when both are measured with the same size back cavity (plenum). Notably, some of our acoustic panels with a 5 cm back cavity outperform Class A panels with a 20 cm back cavity. The absorption coefficient of some of the acoustic panels with different pattern and back cavity of 5 cm are shown. As can be seen, with this short back cavity, the panel has 50% at 100 Hz and between 50% to 99.9% absorption at frequencies between 100 Hz and 4000 Hz. In addition, the absorption coefficient of some otherAtty Docket No. TUOE.P2015WO / 00679628Acoustic Jacket (AJ) samples with total thickness between 1 cm to 4 cm and Acoustic Panels (AP) total thickness including back cavity between 2.5 cm to 6 cm can absorb 65% at ultra-low frequencies and absorb up to 99% at low frequencies between 100 Hz and 1000 Hz. Acoustic panels according to the present disclosure can be advantageously used to build an acoustic enclosure, such as an acoustic room, wherein the walls, ceiling, and / or floor include one of more mufflers according to the present disclosure. Preferably at least walls and ceiling comprise one or more mufflers of the present disclosure.

[0104] Acoustic panels according to the present disclosure can also be provided as acoustic baffles, as described above.Blower Noise Reduction Application

[0105] Fig. 10 shows exemplary embodiments of the present disclosure incorporating an exemplary muffler as described herein, such as the muffler of Fig. 1A-1E, for example, with thicknesses between 1 to 3 mm, to the casings of ventilation and industrial blowers and fans. In an exemplary embodiment, a fan assembly 300 comprises a fan housing 310 enclosing a rotor or impeller 320. The fan housing 310 defines an interior flow path for the air moved by the impeller 320 and includes a region of minimum clearance between the blade tips and the interior wall of the housing, commonly referred to as the fan tongue 330. This tongue region 330 generates elevated aerodynamic noise. The fan assembly 300 further comprises at least one muffler according to the present disclosure, e.g., as shown and described with reference to Fig. 1A-E, configured as an acoustic liner 340 disposed along a surface region of the fan housing 310 in the flow path, for example, the interior interior flow path for the air moved by the impeller 320. The acoustic liner 340 is positioned with a controlled gap 342 from the inner wall of the fan housing 310, the gap typically being on the order of 1 to 3 mm, thereby forming an acoustic back cavity behind the liner 340. Discrete spacing or one or more mounting features such as a plurality of projections may be provided to maintain the gap 342, producing a thin back cavity between the muffler and the inner wall of the fan housing. In other exemplary embodiments, the acoustic liner itself may be provided with a back cavity, such as illustrated in Figs. 2A and 2B. The gap 342 may comprise additional insulation material.

[0106] Structurally, the acoustic liner 340 follows the internal contour of the fan housing and is installed along the circumferential wall. The acoustic liner 340 may be mounted along a selected segment of an interior wall of the fan housing 310 and is preferably located in proximity of the fan tongue region 330. Positioning the acousticAtty Docket No. TUOE.P2015WO / 00679628liner 340 near the tongue 330 yields advantageous attenuation of the noise components generated at this region. However, because the tongue region 330 also has a direct influence on aerodynamic efficiency, the acoustic liner 340 is placed with an offset distance from the tongue, balancing noise reduction with fan performance. In certain embodiments, the acoustic liner 340 extends along a length dimension measured in the circumferential direction of the fan housing 310. The performance of the liner increases with greater length, as a larger effective surface area provides enhanced noise absorption. The width of the liner 340, measured in the axial direction of the housing, may be constrained by the internal geometry of the fan housing 310, and usually will match the width of the unit as fabricated. The length of the acoustic liner along the housing is an important parameter. Short segments provide localized noise reduction, whereas extending the liner over a longer section of the housing improves overall attenuation. In some embodiments, two or more acoustic liners 340 can be provided in the interior and / or exterior walls of the fan housing 310. Where flexible materials are employed in the construction of the acoustic liner 340, its shape may be advantageously contoured to follow the curvature of the fan housing 310, allowing installation in blowers, scroll housings, or radial-fan enclosures.Exhaust Duct Muffler or Silent Pipe Application

[0107] We have developed various configurations of open or closed duct mufflers illustrated in Fig. 1A-1E, with or without a back cavity but with a membrane, that can either minimize reflection or transmission coefficients of the duct muffler to be below 0.1 value. In both scenarios, the mufflers achieve 50 to 90% absorption, particularly at low frequencies, with lengths ranging from 30 to 50 cm. In specific designs and simulations, we achieved |R|<0.3, |Tr|<0.1, and alpha>0.9 for frequencies above 500 Hz with a muffler diameter of 12 cm and a length of 50 cm. These mufflers have no obstacles or baffles in the airflow path along the length of the muffler, ensuring there is low, or no pressure drop, which is a significant advantage compared to current mufflers which usually have baffles through which exhaust must flow. Additionally, they offer high absorption within a limited length and size.

[0108] Figs. 18A and 18B show exemplary ducts or pipes 1800A and 1800B incorporating mufflers according to the present disclosure. Gas, which may be exhaust gas carrying significant sound, or another fluid, enters at one end of a conduit 1802A, 1802B, which includes a muffler construction 1840 A, 1840B according to the present disclosure disposed along at least a portion of the interior of the duct or pipe 1800A,Atty Docket No. TUOE.P2015WO / 006796281800B. Fig. 18A illustrates a pipe or duct 1800A having a muffler structure 1840A enclosed by the first conduit 1802A, while Fig. 18B illustrates a pipe or duct 1800B having a muffler structure 1840B integrated into at least a portion a wall of the first conduit 1802B or otherwise in fluid communication with the interior of the pipe and enclosed by an outer second conduit 1820. The outer second conduit 1820 may be rigid or flexible. An exemplary muffler construction of this embodiment may be implemented by providing an inner tube or tube portion of a muffler 1840A, 1840B formed from at least an inner and a second concentric, closely-spaced, tube formed of parallel and angled strips as previously described. The gas or another fluid that has entered at one end of the conduit 1802A, 1802B exits at another end, having interacted with the muffler construction 1840A or 1840B disposed in an interior flow path of the fluid, with sound reduced; the flowing gas passing by but not through openings of the inner tube. If the tubes are spaced by providing a spacer plate or tube, the inner tube forms the first layer and second tube the second layer. In some embodiments, the muffler has a back cavity formed, for example, by surrounding the inner and second tubes with a third, nonperforated, tube spaced an appropriate distance from the second tube.

[0109] In case of making a short (below 5cm length) closed ducted muffler, it can achieve a reflection coefficient below 0.05 across all frequencies between 20 Hz and 1000 Hz. In specific designs, this effective frequency range can be extended to 4000 Hz.Vessel Noise Reduction

[0110] While the most common use of blades is for use with air in fans, including fan blades of turbofan engines, these blade assemblies are similar in shape to aquatic propellers as commonly used for propulsion of ships and submarines. To quiet aquatic propellers, a surface of each blade of the propeller may be fitted with a muffler. In order to prevent cavitation, avoid clogging from debris, and optimize fluid flow over each blade of the propeller, an acoustic membrane is provided in such exemplary embodiments to prevent fluid flow through the muffler while a back cavity within the blades together with space between layers and within holes of layers is filled with a fluid. While the fluid may be air in some surface-vessel applications, when used in vessel applications, and other applications where pressures may change, the fluid is a noncompressible fluid such as an aqueous fluid or an oil. In these applications plate spacing is determined according to the Stokes boundary layer thickness of the noncompressible fluid within the back cavity and between layers.Atty Docket No. TUOE.P2015WO / 00679628

[0111] The propellers described in the preceding paragraph may be in both unducted and ducted configurations; in a ducted configuration, in addition to forming the muffler on all or a portion of the propeller surfaces, the duct around the propeller may in some embodiments also incorporate the muffler tape herein described to further reduce sound emitted.

[0112] Similarly, muffler tape as previously described, equipped with acoustic membrane and with the back cavity and space between layers filled with noncompressible fluid may be positioned on an exterior surface of machinery spaces and other portions of a ship, submarine, or other vessel. The noncompressible fluid may be chosen from an aqueous or non-aqueous fluid as required for a particular application.

[0113] When the muffler herein described is used on an airfoil or a blade of fan, propeller, or similar device, turbulence generation by air or fluid flow over the ridges formed by the parallel strips may be prevented in part by both making strips of the sheet in contact with the flowing air or fluid, and the aligning strips of the sheet in contact with flowing air or fluid with flow of the air or fluid.COMBINATION OF FEATURES

[0114] (Al) In an embodiment of a first aspect, a muffler includes: a plurality of sheets, each sheet formed of multiple, gapped, parallel strips of a material; at least a first and a second sheet of the plurality of sheets adjacent to each other with the parallel strips of the first sheet at a nonzero angle relative to the parallel strips of the second sheet to form a first layer, gaps between the parallel strips forming a plurality of openings in the first layer; and a structure selected from: a third sheet of the plurality of sheets adjacent the second sheet where channels formed by gaps between the parallel strips of the second sheet form channels between the openings in the first layer and gaps between parallel strips of the third sheet where a majority of openings in the first layer do not align with gaps between the parallel strips of the third sheet, or a second layer formed of a third and fourth sheet of the plurality of sheets with strips of the third sheet disposed at a nonzero angle to the strips of the fourth sheet and spaced less than two millimeters from the first layer, with gaps between strips of the third sheet and gaps between strips of the second sheet aligning to form openings in the second layer where a majority of openings of the first layer do not align with openings of the second layer.

[0115] (A2) In the embodiment (Al) of the first aspect, the structure being a third sheet of the plurality of sheets adjacent the second sheet where channels formed byAtty Docket No. TUOE.P2015WO / 00679628gaps between the parallel strips of the second sheet form channels between the openings in the first layer and gaps between parallel strips of the third sheet.

[0116] (A3) In the embodiment (Al) of the first aspect, the structure being a second layer formed of a third and fourth sheet of the plurality of sheets with strips of the third sheet disposed at a nonzero angle to the strips of the fourth sheet.

[0117] (A4) In the embodiment (A3) of the first aspect, further comprising a spacer layer disposed between the first layer and the second layer, the spacer layer having a plurality of passages coupling openings of the first layer to openings of the second layer.

[0118] (Bl) In an embodiment of a second aspect, a muffler formed of a plurality of parallel, overlapping, strips of material separated by spacers, thickness of the spacers being less than twice Stoke boundary layer thickness at a frequency of interest for the muffler.

[0119] (B2) In the embodiment (Bl) of a second aspect, wherein the plurality of parallel, overlapping, strips are pivoted and configurable in a closed position with strips separated by thickness of the spacers and an open position with strips separated by a distance greater than thickness of the spacers.

[0120] (Cl) In an embodiment of a third aspect, a muffler comprising: a plurality of sheets, each sheet formed of multiple, gapped, shapes of a material; at least a first and a second sheet of the plurality of sheets adjacent to, and attached, to each other to form a first layer with gaps between shapes of the first sheet intersecting gaps between shapes of the second sheet to form holes; and a structure selected from: a third sheet of the plurality of sheets adjacent the second sheet where channels formed by gaps between the gapped shapes of the second sheet extend between the gaps between the shapes in the first layer and gaps between the shapes of the third sheet where a majority of openings in the first layer do not align with gaps between the shapes of the third sheet, or a second layer formed of a third and fourth sheet of the plurality of sheets with holes of the second layer not aligned with holes of the first layer.

[0121] (DI) In an embodiment of a fourth aspect, in any embodiment (Al)-(A4), (B1)-(B2), or (Cl), further comprising a back cavity.

[0122] (El) In an embodiment of a fifth aspect, in any embodiment (A1)-(A4), (B1)-(B2), or (Cl), further comprising a back cavity of depth between one half and one hundred millimeters or of depth between 5 and 50 millimeters.

[0123] (Fl) In an embodiment of a sixth aspect, in any embodiment (DI) or (El), wherein the back cavity contains a sound absorbing material.Atty Docket No. TUOE.P2015WO / 00679628

[0124] (Gl) In an embodiment of a seventh aspect, in any embodiment (DI), (El) or Gl), the back cavity comprising a layer having one or more projections.

[0125] (Hl) In an embodiment of a eighth aspect, in any embodiment (Al)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), or (Gl), further comprising an acoustic membrane.

[0126] (II) In an embodiment of a ninth aspect, in any embodiment (A1)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), or (Gl), wherein strips or shapes of each layer have thickness between 0.01 mm and 5 mm.

[0127] (JI) In an embodiment of a tenth aspect, in any embodiment (A1)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), or (Gl), wherein strips or shapes of each layer have width between 1 mm and 35 mm.

[0128] (KI) In an embodiment of a eleventh aspect, in any embodiment (Al)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), or (Gl), wherein gaps between strips or shapes in a sheet are from 0.5 mm to 25 mm.

[0129] (LI) In an embodiment of a thirteenth aspect, a composite muffler includes a first muffler of any of embodiments (A1)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI) disposed near a second muffler of any of embodiments (A1)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI).

[0130] (Ml) In an embodiment of a fourteenth aspect, a machinery muffler includes a muffler of any of embodiments (A1)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI).

[0131] (Nl) In an embodiment of a fifteenth aspect, a wind turbine blade includes a muffler of any of embodiments (A1)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (Kl)disposed along a wall of the blade, such as at a leading edge and / or a trailing edge of the blade.

[0132] (01) In an embodiment of a sixteenth aspect, a fan blade includes a muffler of any of embodiments (A1)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI) disposed along a wall of the blade, such as at a leading edge and / or a trailing edge of the blade.

[0133] (Pl) In an embodiment of a seventeenth aspect, a muffling tape includes an adhesive layer and a muffler of any of embodiments (A1)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI).Atty Docket No. TUOE.P2015WO / 00679628

[0134] (QI) In an embodiment of an eighteenth aspect, a vehicle hood, wheel cover, and / or body panel, includes a muffler of any of embodiments (A1)-(A4), (Bl)-(B2), (Cl), (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI).

[0135] (Rl) In an embodiment of a nineteenth aspect, an acoustic assembly includes: a muffler; and a back cavity structure positioned posterior to the muffler, wherein the back cavity structure comprises a plurality of adjacent cavity sections within the back cavity structure and at least two of the cavity sections have different volumes.

[0136] (R2) In the embodiment (Rl), wherein the back cavity structure has a substantially uniform depth and comprises at least one internal partition defining the plurality of cavity sections.

[0137] (R3) In either embodiment (Rl) or (R2), wherein the volumes of at least two cavity sections are tuned to a different acoustic resonance frequency.

[0138] (R4) In any embodiment (Rl) through (R3), wherein the muffler comprises channels having a thickness of less than twice Stoke boundary layer thickness at a frequency of interest for the muffler.

[0139] (SI) In an embodiment of a twentieth aspect, a muffler assembly includes: a concrete mass having a first surface and a second surface opposite the first surface; a muffler element disposed on at least one surface of the concrete mass, wherein the muffler element comprises one or more of: a muffler according to any of embodiments (A1)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI), and a plurality of narrow channels formed in the first surface of the concrete mass.

[0140] (S2) The embodiment (SI), wherein the concrete mass is characterized by a porous open-cell structure.

[0141] (S3) In either embodiment (SI) or (S2), wherein the muffler element includes a plurality of narrow channels formed in the first surface of the concrete mass and the length of the narrow channels is at least 5 mm and open area ratio is more than 10%.

[0142] (Tl) In an embodiment of a twenty-first aspect, an acoustic jacket assembly for a noise producing component, such as compressor having a noise producing body, the jacket includes: a jacket body part comprising a muffler element according to a muffler according to any of embodiments (A1)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI), the jacket body configured to at least partially or fully surround the noise producing body.Atty Docket No. TUOE.P2015WO / 00679628

[0143] (T2) In the embodiment (Tl), the jacket further includes a hat portion attachable to an upper region of the jacket body, the jacket body and / or the hat portion comprising at least one opening therein configured to permit one or more pipes to pass therethrough.

[0144] (Ul) In an embodiment of a twenty-second aspect, an acoustic system includes: a noise producing component such as a compressor having a noise producing body and an optional surrounding casing, and an acoustic jacket assembly comprising a jacket body part comprising a sound dampening material; wherein the jacket body part surrounds the noise producing body while being spaced apart from the body over at least a substantial portion of the surface area of the body that is adjacent to the jacket, and preferably wherein the jacket body part is further spaced apart from the casing over at least a substantial portion of the surface area of the casing that is adjacent to the jacket.

[0145] (U2) The embodiment (Ul), further including a mesh disposed between the jacket body part and the body.

[0146] (VI) In an embodiment of a twenty-third aspect, a fan assembly includes: a fan housing defining a flow path and having a wall; and an acoustic liner comprising a muffler according to any of embodiments (A1)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI), disposed along a surface of the wall of the fan housing and in fluid communication with or at least partially in the flow path.

[0147] (V2) The embodiment (VI), wherein the fan housing includes a tongue region, and the acoustic liner is positioned proximate to the tongue region.

[0148] (V3) The embodiment (VI), wherein the fan housing comprises a plurality of acoustic liners according to any of embodiments (A1)-(A4) of the first aspect, (B1)-(B2) of the second aspect, (Cl) of the third aspect, (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI), disposed along a surface of the wall of the fan housing and in fluid communication with or at least partially in the flow path.

[0149] (Wl) In an embodiment of a twenty-fourth aspect, a pipe assembly for conveying a fluid, includes: a first conduit defining an interior and an interior flow path extending between an inlet end and an outlet end of the first conduit; and a muffler according to according to any of embodiments (A1)-(A4) of the first aspect, (B1)-(B2) of the second aspect, (Cl) of the third aspect, (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI) disposed along at least a portion of the interior of the first conduit and in fluid communication with or at least partially in the interior flow path.Atty Docket No. TUOE.P2015WO / 00679628

[0150] (W2) The embodiment (Wl), wherein one or more mufflers according to according to any of embodiments (A1)-(A4) of the first aspect, (B1)-(B2) of the second aspect, (Cl) of the third aspect, (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI) are comprised in an inner tube disposed in the interior of the first conduit.

[0151] (W3) The pipe assembly of embodiment (W2), wherein one or more mufflers according to according to any of embodiments (A1)-(A4), (B1)-(B2), (Cl), (DI), (El), (Fl), (Gl), (Hl), (II), (JI), or (KI) are in fluid communication with or formed in an interior wall of the first conduit and the assembly further comprises a second conduit disposed around the first conduit.

[0152] It will be understood that various embodiments of the present disclosure may include any number and / or combination of the features presented above, as applicable for a particular application.

[0153] Changes may be made in the above methods and systems without departing from the scope hereof. It should thus be noted that the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. For example, the terms top and bottom are used to illustrate the respective relationships of elements of exemplary embodiments of the present disclosure with respect to each other and not their absolute positions in space. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall there between.

Claims

Atty Docket No. TUOE.P2015WO / 00679628ClaimsWhat is claimed is:

1. A muffler comprising:a plurality of sheets, each sheet formed of multiple, gapped, parallel strips of a material;at least a first and a second sheet of the plurality of sheets adjacent to each other with the parallel strips of the first sheet at a nonzero angle relative to the parallel strips of the second sheet to form a first layer, gaps between the parallel strips forming a plurality of openings in the first layer; anda structure selected from:a third sheet of the plurality of sheets adjacent the second sheet where channels formed by gaps between the parallel strips of the second sheet form channels between the openings in the first layer and gaps between parallel strips of the third sheet where a majority of openings in the first layer do not align with gaps between the parallel strips of the third sheet, ora second layer formed of a third and fourth sheet of the plurality of sheets with strips of the third sheet disposed at a nonzero angle to the strips of the fourth sheet and spaced less than two millimeters from the first layer, with gaps between strips of the third sheet and gaps between strips of the second sheet aligning to form openings in the second layer where a majority of openings of the first layer do not align with openings of the second layer.

2. The muffler of claim 1, the structure being a third sheet of the plurality of sheets adjacent the second sheet where channels formed by gaps between the parallel strips of the second sheet form channels between the openings in the first layer and gaps between parallel strips of the third sheet.

3. The muffler of claim 1, the structure being a second layer formed of a third and fourth sheet of the plurality of sheets with strips of the third sheet disposed at a nonzero angle to the strips of the fourth sheet.

4. The muffler of claim 3, further comprising a spacer layer disposed between the first layer and the second layer, the spacer layer having a plurality of passages coupling openings of the first layer to openings of the second layer.Atty Docket No. TUOE.P2015WO / 006796285. A muffler formed of a plurality of parallel, overlapping, strips of material separated by spacers, thickness of the spacers being less than twice Stoke boundary layer thickness at a frequency of interest for the muffler.

6. The muffler of claim 5, wherein the plurality of parallel, overlapping, strips are pivoted and configurable in a closed position with strips separated by thickness of the spacers and an open position with strips separated by a distance greater than thickness of the spacers.

7. A muffler comprising:a plurality of sheets, each sheet formed of multiple, gapped, shapes of a material; at least a first and a second sheet of the plurality of sheets adjacent to, and attached, to each other to form a first layer with gaps between shapes of the first sheet intersecting gaps between shapes of the second sheet to form holes; anda structure selected from:a third sheet of the plurality of sheets adjacent the second sheet where channels formed by gaps between the gapped shapes of the second sheet extend between the gaps between the shapes in the first layer and gaps between the shapes of the third sheet where a majority of openings in the first layer do not align with gaps between the shapes of the third sheet, ora second layer formed of a third and fourth sheet of the plurality of sheets with holes of the second layer not aligned with holes of the first layer.

8. The muffler of any of claims 1 through 7, further comprising a back cavity.

9. The muffler of any of claims 1 through 7, further comprising a back cavity of depth between 0.5 and 100 millimeters.

10. The muffler of claim 8 or 9, wherein the back cavity contains a sound absorbing material.

11. The muffler of claim 8, 9, or 10, the back cavity comprising a layer having one or more projections.

12. The muffler of any of claims 1 through 11, further comprising an acoustic membrane.Atty Docket No. TUOE.P2015WO / 0067962813. The muffler of claim any of claims 1 through 12, wherein strips or shapes of each layer have thickness between 0.01 mm and 5 mm.

14. The muffler of claim any of claims 1 through 12, wherein strips or shapes of each layer have width between 1 mm and 35 mm.

15. The muffler of claim any of claims 1 through 12, wherein gaps between strips or shapes in a sheet are from 0.5 mm to 25 mm.

16. A composite muffler comprising a first muffler of any of claims 1 through 15 disposed near a second muffler of any of claims 1 through 15.

17. A machinery muffler comprising a muffler of any of claims 1 through 15.

18. A wind turbine blade comprising a muffler of any of claims 1 through 15 disposed along a wall of the blade, such as at a leading edge and / or a trailing edge of the blade.

19. A fan blade comprising a muffler of any of claims 1 through 15 disposed along a wall of the blade, such as at a leading edge and / or a trailing edge of the blade.

20. A muffling tape comprising an adhesive layer and a muffler of any of claims 1 through 15.

21. A vehicle hood, wheel cover, or body panel, comprising a muffler of any of claims 1 through 15.

22. An acoustic assembly comprising:a muffler; anda back cavity structure positioned posterior to the muffler,wherein the back cavity structure comprises a plurality of adjacent cavity sections within the back cavity structure and at least two of the cavity sections have different volumes.

23. The acoustic assembly of claim 22, wherein the back cavity structure has a substantially uniform depth and comprises at least one internal partition defining the plurality of cavity sections.

24. The acoustic assembly of claim 22 or 23, wherein the volumes of at least two cavity sections are tuned to a different acoustic resonance frequency.Atty Docket No. TUOE.P2015WO / 0067962825. The acoustic assembly of any of claims 22 to 24, wherein the muffler comprises channels having a thickness of less than twice Stoke boundary layer thickness at a frequency of interest for the muffler.

26. A muffler assembly comprising:a concrete mass having a first surface and a second surface opposite the first surface; a muffler element disposed on at least one surface of the concrete mass, wherein the muffler element comprises one or more of: a muffler according to any of claims 1 through 15, and a plurality of narrow channels formed in the first surface of the concrete mass.

27. The muffler assembly of claim 26, wherein the concrete mass is characterized by a porous open-cell structure.

28. The muffler assembly of claim 27, wherein the muffler element comprises a plurality of narrow channels formed in the first surface of the concrete mass and the length of the narrow channels is at least 5 mm and open area ratio is more than 10%.

29. An acoustic jacket assembly for a noise producing component having a noise producing body, the jacket comprising:a jacket body part comprising a muffler element according to any of claims 1 through 15, the jacket body configured to at least partially or fully surround the noise producing body.

30. The acoustic jacket assembly according to claim 29, the jacket further comprising a hat portion attachable to an upper region of the jacket body, at least one of the jacket body and the hat portion comprising at least one opening therein configured to permit one or more pipes to pass therethrough.

31. An acoustic system comprising:a noise producing component having a noise producing body and an optional surrounding casing, andan acoustic jacket assembly comprising a jacket body part comprising a sound dampening material;wherein the jacket body part surrounds the noise producing body while being spaced apart from the noise producing body over at least a substantial portion of the surface area of the body that is adjacent to the jacket, and preferably wherein the jacket body part is spacedAtty Docket No. TUOE.P2015WO / 00679628apart from the casing over at least a substantial portion of the surface area of the casing that is adj acent to the j acket.

32. The acoustic system of claim 31, further comprising a mesh disposed between the jacket body part and the noise producing body.

33. A fan assembly comprising:a fan housing defining a flow path and having a wall; andan acoustic liner comprising a muffler according to any of claims 1 through 15, disposed along a surface of the wall of the fan housing and in fluid communication with or at least partially in the flow path.

34. The fan assembly of claim 33, wherein the fan housing includes a tongue region, and the acoustic liner is positioned proximate to the tongue region.

35. The fan assembly of claim 33, wherein the fan housing comprises a plurality of acoustic liners according to any of claims 1 through 15, disposed along a surface of the wall of the fan housing and in fluid communication with or at least partially in the flow path.

36. A pipe assembly for conveying a fluid, comprising:a first conduit defining an interior and an interior flow path extending between an inlet end and an outlet end of the first conduit; anda muffler according to any of claims 1 through 15 disposed along at least a portion of the interior of the first conduit and in fluid communication with or at least partially in the interior flow path.

37. The pipe assembly according to claim 36, wherein one or more mufflers according to any of claims 1 through 15 are comprised in an inner tube disposed in the interior of the first conduit.

38. The pipe assembly according to claim 36, wherein one or more mufflers according to any of claims 1 through 15 are in fluid communication with or formed in an interior wall of the first conduit and the assembly further comprises a second conduit disposed around the first conduit.

Images