Abstract: An air filter for an internal combustion engine includes an air filter housing, the walls of which encompass a filter compartment in which a filter element is positioned, having an intake and an exhaust. Openings that can be sealed off or opened up based upon the operating conditions of the internal combustion engine are provided in a least one wall of the air filter housing. In this way, effective modulation of induction noise (sound modulation) can be achieved in a simple way and manner.

Abstract: An acoustical panel comprising a continuous phase of an interlocking set gypsum matrix and a method of preparing an acoustical panel are disclosed.

Abstract: An automotive vehicle sound absorption system. An expandable material, such as an polymer-based foam, is disposed on a surface of a wall. Upon activation, the foam transforms, preferably during an automobile assembly operation, and remains bonded to surface for sound absorption.

Abstract: Apparatus and methods are provided forming a sound attenuating laminate that has a decoupler fiber layer and a mass layer in opposing relationship with each other. The decoupler fiber layer and mass layer of the laminate are heated to the selected temperature in substantially the same amount of time via a hot air source and a heated platen, respectively. The heated laminate is conveyed to a mold and formed into a predetermined three-dimensional configuration via the mold.

Abstract: A vehicle seat cover is designed to facilitate acoustic energy absorption by forming in the cover an optimal size and arrangement of perforations based on at target noise frequency range, the perforations allowing the noise to pass through the cover into the interior structure of the seat where the acoustic energy is dissipated in the form of heat.

Abstract: The present invention is a flow control actuator capable of exciting a fluid via the coupling of edge tones generated along a wedge and resonance generated within a cavity. The invention consists of a resonance cavity and ejector port separated by a wedge with fluid flow provided by a pressurized cavity and directed through a throat over the wedge. Several actuators may be arranged independently or in a coupled arrangement to generate a pulsed fluid field of desired shape.

Abstract: Sound attenuating laminates, and methods of making the same, are provided. Heat is applied to a surface of a non-woven, fibrous layer of material to form a stratum of melted fibers having a density greater than that of the remainder of the fibrous layer. The density of the melted fibers is effective in attenuating noise traversing the fibrous layer of material. Upholstery material, such as carpeting, is attached to the surface of the heated fibrous layer. The fibrous layer and upholstery material are then subjected to compressive molding pressure to obtain a desired shape. The compressive molding pressure may further tune the sound attenuating properties of the fibrous layer by selectively changing the densities of portions of the fibrous layer.

Abstract: The present invention relates to methods of attenuating underwater transmission of sound or shock waves as well as boom systems designed for such use. The boom system is characterized by a material (e.g., curtain or combination curtain and skirt) which extends substantially the entire water column when placed in a body of water, thereby defining a perimeter and a gas injection system which includes a plurality of outlets which are positioned between the perimeter and the site of underwater activity. In use, the boom system is installed such that it surrounds the site of underwater activity and then gas is injected into the water through the plurality of outlets to form a gas curtain during performance of an underwater activity capable of generating sound or shock waves.

Abstract: Sound attenuating composite articles and methods of making same are provided. Sound attenuating composite article include first, second and/or third and/or fourth layers of material. The first layer of material may be either an acoustic fiber batting and/or an acoustic foam material and may be an elastic or inelastic material. The second layer of material is a thermoplastic material that is fused to a surface of the first layer of material. The third layer of material is a thermoplastic material that is fused to a surface of the second layer of material. The fourth layer of material is a woven or non-woven mixture of fibers, such as scrim material, that is attached to a surface of the third layer of material. Selected portions of the sound attenuating composite article are heated and then compressed (referred to as “tuned”) so as to have an acoustic impedance that is greater than an acoustic impedance of adjacent portions.

Abstract: A method of making an acoustical panel includes providing a fiberglass substrate, applying an adhesive to the substrate, and applying a facing to the adhesive. The resulting acoustical panel laminate has a smooth exterior face. Further, an acoustical panel includes a rigid fiberglass board, an adhesive layer, and a fiberglass mat coupled to the fiberglass board by the adhesive layer.

Abstract: A method for fabricating an acoustic resonator, for example a Thin Film Bulk Acoustic Resonators (FBAR), on a substrate. A depression is etched and filled with sacrificial material. The FBAR is fabricated on the substrate spanning the depression, the FBAR having an etch hole. The depression may include etch channels in which case the FBAR may include etch holes aligned with the etch channels. A resonator resulting from the application of the technique is suspended in air and includes at least one etch hole and may include etch channels.

Abstract: In the manufacture of a noise attenuation panel for an aeroengine nacelle an adhesive film is applied to a front face of a cellular component of the panel. The adhesive film is caused to reticulate to the ends of the walls of the cells at the front face of the cellular component. A perforate facing component of the panel is bonded to the front face of the cellular component by adhesive flow from the cell walls to the facing component. To avoid unpredictable adhesive flow giving rise to cosmetic spots on the front face of the facing component the two components are brought together with the interposition of an adhesive flow control sheet and the reticulated adhesive caused to bond the two components together by adhesive flow under the control of the adhesive flow control sheet.

Abstract: The modular anechoic panel system provides modular anechoic panel for construction of anechoic chambers particularly advantageous for use in sound testing and measurement. The modular anechoic panel incorporates into a single structural member the elements of structural support, transmission loss features, and the wedge base and air space elements of an anechoic wedge thus providing enhanced protection to elements of the anechoic wedge. The modular anechoic panel provides a durable structural member and, as assembled, form a structural shell of an anechoic chamber having a reduced footprint. Additionally, the modular anechoic panel provides a compression clip mounting system for conveniently mounting and replacing wedge tips, thus allowing for use of standard wedge tip materials and easy assembly, repair and replacement of damaged wedge tips.

Abstract: A sound insulating structure (12) comprises first layer plates (30) arranged in coplanar and contiguous relationship in order to form a first structural layer, second layer plates (13) arranged in coplanar relationship in order to form a second structural layer in spaced parallel relation with the first structural layer, and a core (6), which core effectively bridges the space between and adheres together plates of the respective layers, and which core comprises an elastic, vibration deadening mass. At least one through opening is provided in each of the second layer plates with the purposes of permitting escape of any trapped air and of permitting inspection of the space between the structural layers while the mass in the core sets to an elastic state. The invention also provides a panel and a method of manufacturing a sandwich board.

Abstract: A microporous sheet having both acoustical and structural functionality and a process for producing the sheet. Construction of the sheet requires, first of all, providing a sheet capable of functioning as a structural element of a component. A laser device capable of producing a free electron laser beam is provided, and the free electron laser beam is directed to a surface of the sheet to penetrate the sheet at a plurality of sites and thereby form a plurality of apertures. These apertures are generally uniformly dispersed and of a size and number sufficient to enable the sheet to function as an acoustical noise suppressor while retaining capability of functioning as a structural element.

Abstract: A vibration damped structure, which is excellent in vibration absorption and sound absorption effect, is provided by coating the surface of a structure to be damped with a mixture of molten photopolymerizable resin and a photopolymerization initiator and then subjecting the coated surface to irradiation, whereby a vibration damping coating is formed on said surface.

Abstract: A process for production of a tube profile element having a swaged closed head end includes the steps of chamfering an unswaged end of a tube profile element having a first diameter to provide a chamfered end on the tube profile element having a chamfer angle of less than 45° relative to a longitudinal axis of the end portion of the tube profile element, supporting the tube profile element in a retaining tool such that an end portion of the tube profile element having the unswaged chamfered end thereon extends beyond the retaining tool, providing a swage tool having a negative die capable of swaging the end portion of the tube into a swaged closed head end having a maximum second diameter larger the first diameter of the unswaged end of the tube, and moving the swage tool toward the end portion of the tube and swaging the unswaged chamfered end of the tube, by the negative die of the swage tool, into the swaged closed head end of the tube profile element.

Abstract: Method for filling cavities in workpieces or semi-finished products is provided, in which thermally foamable powdered carbon is added in fixed locations into the cavity to be filled and is heated together with the workpiece or semi-finished product in such fashion that the powdered carbon swells and fills the cavity as carbon foam, with the particles of powdered carbon in the delivered state being smaller than after foaming. A structural component is formed, especially a workpiece or semi-finished product for mounting on or in a motor vehicle body, having an enclosed chamber in which thermally foamable powdered carbon is added in a fixed location, with the powdered carbon being heated together with the structural element to swell the powdered carbon and form carbon foam.

Abstract: The acoustic tower of the present invention is a portable, acoustic tower that has both a performance position and a storage position. In the storage position, a canopy panel lies substantially parallel proximate an upper panel, both of which are hingedly secured to a cross tube assembly that is supported by a lift tube. The upper panel lies substantially parallel to a lower panel that is fixedly secured to a lower panel assembly having side supports and a center shaft which substantially contains the lift tube. To raise the acoustic tower to the performance position, the canopy panel is raised to one of a plurality of preset angles and maintained in position through use of ratchet and pawl assemblies of the cross tube assembly. With the canopy panel at the desired angle, the upper panel and canopy panel are raised vertically by telescopically elevating the lift tube within the center shaft. The lift tube is elevated by virtue of a winch assembly that is connected to the lift tube by a length of webbing.

Abstract: The invention relates to a soundproofing window in which an intermediate film provides for damping of vibrations transmitted in particular by structure-borne conduction.

Abstract: An elevator controller 7 is provided with logic 48 which automatically calculates a motor time constant (.tau..sub.R), a torque constant (K.sub.T *), and a magnetizing current (Id) for a field-oriented motor/drive system by calculating a transient inductance L.sigma., injecting a variable input frequency sinewave into a q-axis reference current I.sub.qREF and varying the input frequency while calculating an imaginary part of a rotor impedance Imag(Z.sub.R) to obtain a frequency (F.sub.PEAK) at which the maximum value of Imag(Z.sub.R) occurs, then calculating .tau..sub.R from F.sub.PEAK. K.sub.T *, Id, and a total motor voltage V.sub.M are calculated and Id is varied until a ratio of rated motor voltage (Vph.sub.-- RATED) to V.sub.M is within a predetermined tolerance of one. The procedure is performed with the rotor locked.

Abstract: Noise is attenuated through use of an acoustical insulation 10 that includes a molded, three-dimensional nonwoven web that contains organic microfibers 12 and heat activatable staple fibers 14 where the heat activatable staple fibers 14 are bonded to each other and to the microfibers 12 at various contact points. The web contains greater than 15 weight percent heat activatable staple fibers, has a thickness of about 0.5 centimeters or greater, and a density of less than 250 kilograms per cubic meter and preferably contains bulking staple fiber 16. The acoustical insulation is positioned between a source area and a receiving area such that a major face of the insulation intercepts and thereby significantly attenuates sound waves passing from the source area to the receiving area.

Abstract: A rigid acoustic insulator panel for use as a sound insulator is disclosed. The panel is composed of a rigid matrix formed of randomly oriented, fused silica fibers having fiber diameters predominantly in the range between 0.5 and 2 .mu.m. The matrix has a three-dimensionally continuous network of open, intercommunicating voids, and a density of between about 2 and 6 lb/ft.sup.3. In one embodiment, the panel has greater flow resistance characteristics, progressing from a sound-absorbing side of the matrix to the opposite panel side. Also disclosed is a method of preparing the panel.

Abstract: Acrylate-only and epoxy-acrylate thermoset resins exhibit high temperature damping behavior. These materials are suitable for damping vibrations in structures and component parts of devices where high temperature performance is required, such as in automobiles, aircraft, industrial equipment and appliances.

Abstract: An acoustic structure for use as a sound insulator in a jet engine is disclosed. The structure, which is carried in a sound-absorbing compartment of the engine, includes a framework and an acoustical insulation material disposed within the framework. The material is composed of a rigid matrix of randomly oriented, fused silica fibers having fiber diameters predominantly in the range 2-8 .mu.m, a three-dimensionally continuous network of open, intercommunicating voids, a flow resistivity between about 10-200K rayls/m, and a density of between about 2 and 8 lb/ft3. Also disclosed are a clad acoustical structure for sound attenuation in a jet engine, where operational temperatures exceed current jet engine designs, and a method of attenuating jet engine noise.

Abstract: In order to abate unwanted noise having as its source a stack or duct of large cross-sectional dimension, a venturi is installed in the duct such as to suppress at least the highest order modes of sound propagation in the stack or duct. The invention is most useful with stacks or ducts having a cross-sectional dimension exceeding 50 cm.

Abstract: The invention relates to an acoustic insulation screen. The screen comprises a cushion (5) consisting of a flexible bag (4) inflated with a gas under pressure and allowing the gas to flow freely inside the bag, said bag being selected so as not to transmit vibration energy from one point of the bag to another, and the gas being selected from gases in which the speed of sound is greater than the speed of sound in the air. The invention applies particularly to the protection of the payload compartment in a launcher.

Abstract: A new and improved method and apparatus for an acoustical partition are presented. The acoustical partition comprises a wall section defining an enclosed space, a frame structure contained within the wall section, and an insulation layer contained within the frame structure such that an air cavity is created at the centermost area within the wall section. The acoustical partition may also include a sound absorption layer placed on a front side of the wall section, and a fabric layer positioned over the sound absorption layer in such a way as to provide an airspace between the sound absorption layer and the fabric layer.

Abstract: An acoustic shell tower module of sound enhancing character assemblable with other such towers to form an orchestral shell, has a first sound enhancing panel mounted on a generally horizontally rearwardly extending counterweighting base. A second sound enhancing panel is mounted for vertical telescoping movement from a storage position, generally horizontally aligned with the first panel, upwardly to a raised position in which it extends above the first panel to form a sound reflecting and enhancing upper extension thereof, and a system is provided for easily raising and lowering the second panel and retaining it in raised position.

Abstract: A two-dimensional primitive root diffusor includes a two-dimensional pattern of wells, the depths of which are determined through operation of primitive root sequence theory. A prime number N is chosen such that N-1 has two coprime factors which are non-divisible into each other. From the prime number, a primitive root is determined and, in the preferred embodiment, an algorithm is used to determine sequence values for each well. Each sequence value is proportional to the well depth, with each sequence value being multiplied by the design wavelength and then divided by 2N to arrive at the actual well depth value.

Abstract: A method and article for damping acoustic energy caused vibrations comprises forming a damping surface comprising an alloy containing from about 13.5 to about 24.5 atom percent tin with the balance being essentially titanium or a titanium-chromium alloy containing from about 52 to about 56 atom percent chromium, about 8 to about 12 atom percent aluminum, and the balance essentially titanium.

Abstract: A method for attenuating sound waves passing from a source area to a receiving area comprises the steps of providing a nonwoven acoustical insulation web comprising thermoplastic fibers, the web having an average effective fiber diameter of less than about 15 microns, a density of less than about 50 kg/m.sup.3, and an air pressure drop across the web of at least about 1 Mm water at a flow rate of about 32 liters/min.; and positioning the web between the source area and the receiving area such that a major face of the web intercepts and thereby attenuates sound waves passing from the source area to the receiving area. Also, a laminate adapted to be applied to the inner panel of a vehicle door comprises the web and a second layer, such as a scrim, nonwoven fabric, film, or foil, laminated thereto. The laminate can be applied to the inner panel of a vehicle door so that the second layer provides water barrier protection and the web provides acoustical insulation.

Abstract: For under hood sound-deadening of vehicles a molded sheet (14) of impregnated non-woven fabric sheet material having a weight in the range 0.5 to 0.75 kg/m.sup.2 and a density in the range of 350 to 425 kg/m.sup.3 is used. The material includes a blend of polyester staple fibers having an average decitex in the range 2.5 to 4.0 dtex typically 3.2 dtex. The impregnant includes 10 to 35% by dry weight carboxylated styrene-butadiene copolymer in which the styrene content is not less than 55%, 5 to 10% by dry weight carboxylated styrene-butadiene copolymer in which the styrene content is not more than 50%, 50 to 70% by dry weight mineral filler, and up to 3.5% by dry weight melamine formaldehyde resin. Pigment may also be added. The fabric sheet material is preferably clipped to the hood underside to provide a small air gap between the material and the hood, but alternatively the sheet material may be bonded by adhesive to the hood underside.

Abstract: A noise reduction method using a muffler for connection to the air inlet of an air compressor including an imperforate, hollow housing enclosing a chamber, air inlet and outlet openings in the housing, an air inlet tube in the housing connected to the air inlet opening and an air outlet tube in the housing connected to the air outlet opening, both tubes extending over half the length of the chamber, and the openings in the distal ends of the tubes facing in the opposite directions.

Abstract: An apparatus and method for suppressing acoustic noise utilizes consecutive plates, closely spaced to each other so as to exploit dissipation associated with sound propagation in narrow channels to optimize the acoustic resistance at a liner surface. The closely spaced plates can be utilized as high temperature structural materials for jet engines by constructing the plates from composite materials. Geometries of the plates, such as plate depth, shape, thickness, inter-plate spacing, arrangement, etc., can be selected to achieve bulk material-like behavior.

Abstract: Heat shrink tubing is disposed about a pneumatic tool and heat shrunk into position on the tool. Foraminous material is located between the tubing and tool in a restricted fluid-flow passageway extending between a tool air flow outlet and an end of the heat shrunk tubing.

Abstract: A new and improved muffler for use particularly with internal combustion engines which utilizes a tube assembly composed of a plurality of laterally nested tubes in direct supporting lateral engagement with each other providing direct communication therebetween through perforations in the tubes. The tube assembly is supported at opposite ends by frustoconical entrance and exit collars, the larger ends being crimped or otherwise secured thereto providing a sealed connection.

Abstract: A trapezoidal-shaped acoustic absorber is designed for use in music recording studios. The absorber is configured in the shape of a right trapezoidal prism and has an internal transverse pegboard partition which divides the absorber into a plurality of chambers. Each of the chambers is lined with fiberglass sound insulation padding and is resonant to a different frequency. The unit as a whole is resonant to still another frequency. A plurality of the modules are assembled together to line the walls or ceiling of a room so as to render the room suitable for mixing and recording musical sounds. The modular units are portable and allow audio recording and mixing to be formed in virtually any room without the necessity for access to a specially designed recording studio.

Abstract: A noise attenuation barrier for control of noise along expressway or other noise sources is provided in which the panel sections are suspended on vertical posts installed in earth berms. The bottoms of the panels, which are shaped to match the contour of the berm are partly buried in a particulate, sound-absorbing layer. The panels include an imperforate rear wall, spaced away from which is a sound-absorbing layer held in place by edge strips that are fit over the tops and bottoms of the layer before it is put in place.

Abstract: A speaker and manufacturing method therefor includes a diaphragm having an integral edge, first and second frame pieces and a driver unit. The first and second frame pieces are formed by molding so that the first frame piece is integrally combined with the diaphragm edge, and the second frame piece is integrally combined with the driver unit.

Abstract: An apparatus for and method of suppressing noise generated by the primary exhaust gas flow from jet engine nozzles or the like without significantly affecting thrust. A secondary jet stream is provided exteriorly of the primary exhaust gas flow for interacting at the boundary between the exhaust gas flow and the ambient air immediately adjacent the exit end of the nozzle to preclude the formation and propagation of noise generating phenomena. The pressure of the secondary jet stream can be varied in accordance with noise levels sensed at the nozzle exit end to provide optimum noise suppression under essentially all conditions of exhaust gas flow.

Abstract: A process for preparing a wholly carbonaceous integrated diaphragm for acoustic equipment use comprises blending under application of high shearing force a mixture of one or more kinds of organic high polymeric substances carbonizable on baking and powder of graphite with crystals high elastic modulus developed therein; extrusion-molding the uniformly blended and dispersed mixture through a profile extrusion die to give a core material with orientation along the direction of the extrusion and to be cut to a desired form; independently blending and sheeting under application of high shearing force the mixture with the organic powder oriented to high degree parallel to the direction of the surface of the sheet and further passing the sheet through a calendering roll to give a skin material in the form of a film or sheet; bonding said skin material on both sides of the core material by the use of such organic liquid composition that provides high yield of carbon residue on baking and then baking the resulting un

Abstract: When there is relative movement, at a speed above a critical value, between the trailing edge of a body, such as a hydrofoil or aerofoil section, and a fluid, the fluid flow tends to form a pattern of discrete swirling vortices. Vortex shedding at each side of the trailing edge alternately can cause resonance or "singing" of the section. The effect of this phenomenon is reduced by forming contiguous triangular flat-faced notches in the major surfaces of the section, adjacent the trailing edge, but leaving the profile of the leading edge substantially undistrubed. The notches in one major surface are preferably staggered relative to those in the other major surface.

Abstract: An engine exhaust apparatus in which an exhaust passageway of the engine is provided with a plurality of sound deadening passsages. One common exhaust passageway from the engine is branched into first and second exhaust passageways. Each of the first and second exhaust passageways has a silencer or muffler including first and second exhaust outlet tubes with a shift valve mounted in one of these exhaust outlet tubes. A control unit controls the shift valves to close both when engine speed is in a low region, to open one of them when engine speed is in a medium region and to open both when engine speed is in a high region.

Abstract: A silencer device is installed into the discharge pipe of a centrifugal compressor by first installing a channel shaped frame in the discharge pipe and then sliding the silencer device into the frame to be contained for operational use. The orientation and placement of the frame and its contained silencer device is parallel with the direction of flow to thereby reduce the resulting pressure drop, and it is placed near a turn in the discharge pipe such that the sound will tend to be reflected from the discharge pipe to cause multiple passes through the silencer device and thereby enhance its absorptive performance. The absorptive material within the silencer device is protected from erosion by a surrounding cloth bag composed of a fine weave Nomex material.

Abstract: A movable, prefabricated wall panel having a rigid frame. Internal to the rigid frame is a structural acoustical core, consisting of a grid with a plurality of individual cells, each filled with insulation media, such as a loose, discrete insulation such as fiberglass, cellulose, etc. The outer surfaces of the cell grid are covered with a skin or screen mesh for confining the loose discrete insulation. This skin or mesh can be a finished decorative outer cover or an intermediate component that is later covered with a decorative outer cover of fabric or other suitable material. A septum may be provided in the panel in the grid and may be made of a pliable, sound absorbing material. Additional acoustic barrier panels may be sandwiched on either side of the cellular grid.

Abstract: A compressor bleed air passageway includes a duct having an upstream section (48) which terminates in a baffle (44) and a downstream duct section (54) having a forward portion (56) which surrounds the baffle (44). Bleed air flow through openings (58) in the baffle wall (52). This reduces velocity of the bleed air stream at the duct discharge port to a value equal to or less than Mach 1.0. The baffle (44) has virtually no effect on a low-velocity, low-pressure air stream. The downstream duct section (54) may be perforated and surrounded by outer wall (64) to form sound-absorbing chambers (66).

Abstract: The present noise reduction system provides a tool and a method to dampen the vibration of sheet material such as a panel, a metal sheet or a skin while performing a manufacturing operation on it, for instance riveting, drilling, etc. This noise reducing tool is held in place by vacuum and thus avoids the disadvantages associated with gluing and mechanical or magnetic fixing devices. This noise reducing tool includes a flexible pad made of a metal back sheet with a vibration damping sheet adhered to it and having an air seal surrounding the damping sheet such that the pad is held against the panel by action of a vacuum intermediate the damping sheet and the panel.

Abstract: A ring damper for reducing vibration and structureborne noise propagation piping systems, comprising a metal ring that is clamped circumferentially around the outer surface of the pipe or duct, said ring defining an annular chamber or cavity that is stuffed with a combination of damping materials.

Abstract: A method for attenuating sound waves passing from a source area to a receiving area comprises the steps of providing a nonwoven acoustical insulation web comprising thermoplastic fibers, the web having an average effective fiber diameter of less than about 15 microns, a density of less than about 50 kg/m.sup.3, and an air pressure drop across the web of at least about 1 Mm water at a flow rate of about 32 liters/min.; and positioning the web between the source area and the receiving area such that a major face of the web intercepts and thereby attenuates sound waves passing from the source area to the receiving area. Also, a laminate adapted to be applied to the inner panel of a vehicle door comprises the web and a second layer, such as a scrim, nonwoven fabric, film, or foil, laminated thereto. The laminate can be applied to the inner panel of a vehicle door so that the second layer provides water barrier protection and the web provides acoustical insulation.