Abstract: A straddle-type vehicle 30 includes a vehicle body frame 31, an engine 1 mounted on the vehicle body frame 31, combustion adjusting devices (fuel injection valves) 14 and 15 for adjusting the combustion condition of the engine 1, and a combustion controller (ECU) 22 for controlling the fuel injection valves 14 and 15. The ECU 22 controls the fuel injection valves 14 and 15 such that the maximum point of a sound pressure level waveform of an audible sound wave generated from the engine 1 or the vehicle body frame 31 is shifted by a predetermined amount or larger within a predetermined period at least in some of the operation conditions of the engine 1.

Abstract: A turbojet engine nacelle includes at least one nacelle element having a wall delimiting a main flow channel. The flow channel has a variable flow passage section. The cross-sectional area of at least one first area of the channel is greater than that of at least one second area of the channel. The turbojet engine nacelle further includes at least one secondary flow conduit establishing a fluidic connection between the first area and the second area of the channel and is arranged parallel to the channel. The wall of the nacelle element is at least partly covered by an acoustic damping panel extending in said areas of the channel. The conduit passes through the acoustic damping panel in order to establish the secondary flow via the acoustic damping panel. The present invention can be used in the avionics field.

Abstract: Apparatuses are provided for reducing noise generation from a dead ended conduit in a gas turbine engine. In particular A scooped bellmouth is provided that comprises a bellmouth within a surface having an outer perimeter an inner perimeter and a ramp diverging from the surface at a first end, the ramp extending radially through the outer perimeter of the bellmouth at a second end. The ramp diverts an airflow away from the bellmouth thereby preventing the development of a low pressure area at the bellmouth without affecting the efficiency of the gas turbine engine.

Abstract: An acoustic structure (e.g. an acoustic tuning panel) includes a plurality of boards and a plurality of resonance tubes with a plurality of openings. The openings are formed at different positions on the side faces of the resonance tubes. One resonance tube may be interposed in and supported by a pair of boards, or one board may be interposed in and supported by a pair of resonance tubes. The resonance tubes are mutually movable in the axial direction so as to independently adjust the opening area of the opening of the resonance tube. With this behavior, it is possible to adjust a ratio of the opening area of the resonance tube to the sectional area of the internal cavity of the resonance tube, thus adjusting the bandwidth of a band causing a sound-absorbing effect and a sound-scattering effect in an acoustic space (e.g. a sound chamber).

Abstract: An aircraft nacelle includes a wave attenuation panel which limits or prevents the propagation of at least one wave produced during the pumping of the power plant and includes a layer that is in contact with the air flow that can allow passage of the at least one wave, at least one alveolar structure, and a reflective or impermeable layer, wherein the wave attenuation panel is inserted between the air intake and the power plant, and the layer that is in contact with the air flow ensures the continuity of the aerodynamic surfaces that are arranged downstream and upstream and the wave attenuation panel includes inserts that can be inserted between the air intake and the power plant so as not to crush the wave attenuation panel.

Abstract: An acoustic damper arrangement for a combustor which has an inner liner configured for use at a first temperature during operation and an outer liner configured for operation at a second temperature lower than the first temperature during operation is disclosed, the acoustic damper arrangement comprising: a plurality of flexible sheets; and at least one hollow body having an interior volume, each of said at least one hollow body being fixed to one of the plurality of flexible sheets, wherein the acoustic damper arrangement is configured to be fixed to both the inner liner and the outer liner such that the interior volume of the at least one hollow body is in communication with a chamber formed by the inner liner, and the plurality of flexible sheets accommodate expansion and contraction of the inner liner relative to the outer liner.

Abstract: Monolithic acoustically-treated composite structures and methods for fabricating the same are provided. A monolithic acoustically-treated composite structure comprises an internal frame assembly comprising a unitary composite frame structure and at least one acoustic panel assembly. The unitary composite frame structure defines a shape of the monolithic acoustically-treated composite structure to be fabricated. A composite overlay covers the internal frame assembly. The method for fabricating the monolithic acoustically-treated composite structure comprises forming the unitary composite frame structure, including the at least one acoustic panel in the unitary composite frame structure, and covering the internal frame assembly with the composite overlay.

Abstract: An acoustic damper arrangement for a combustor which has an inner liner configured for use at a first temperature during operation and an outer liner configured for operation at a second temperature lower than the first temperature during operation is disclosed, the acoustic damper arrangement comprising: a plurality of flexible sheets; and at least one hollow body having an interior volume, each of said at least one hollow body being fixed to one of the plurality of flexible sheets, wherein the acoustic damper arrangement is configured to be fixed to both the inner liner and the outer liner such that the interior volume of the at least one hollow body is in communication with a chamber formed by the inner liner, and the plurality of flexible sheets accommodate expansion and contraction of the inner liner relative to the outer liner.

Abstract: A noise reduction assembly located at a junction plane between an air intake structure and a fan casing of an aircraft turbojet has improved acoustic properties since the alternation of acoustic and non-acoustic zones is displaced or eliminated. In particular, the inner wall of the air intake structure includes a projecting part that extends towards the aft direction beyond the junction plane, in other words the flange of the fan casing. The projecting part may be sufficiently long so that its inner skin is continuous as far as the limit between the acoustic zone and the non-acoustic zone of the nacelle.

Abstract: An aircraft nacelle includes an air intake that makes it possible to channel the air in a pipe in the direction of a pipe of a power plant that is arranged in the extension of the pipe, whereby the pipe of the air intake includes at least one panel that integrates an acoustic treatment with an acoustically resistive porous layer that is in contact with the aerodynamic stream that enters into the nacelle, at least one alveolar structure, and a reflective or impermeable layer that forms the rear surface of the panel, a flange that ensures the connection between the air intake and the power plant including at least one wing that is connected to the air intake by a number of connecting elements, characterized in that some of the connecting elements have axes that are secant with the edge of the panel that delimits the pipe of the air intake.

Abstract: A liner assembly for an aircraft engine housing includes a noise attenuation structure that is covered by a face sheet. The face sheet covering the noise attenuation structure includes a surface having a plurality of circumferentially spaced apart acoustic energy absorption areas that are interspersed between a corresponding plurality of acoustic energy reflective areas. The acoustic energy reflective areas scatter higher order acoustic modes into a plurality of lower order modes. The difficult to attenuate lower order acoustic modes produced by the various acoustic energy cancel each other out to provide significant improvement in liner noise reduction efficiency.

Abstract: A filter silencer is disclosed. In a particular embodiment, the silencer includes a housing, a silencer chamber disposed inside the housing, and a filter chamber disposed between a sidewall of the housing and the silencer chamber. An intake port is in communication with the filter chamber and ambient air. The filter chamber also includes a filter chamber outlet that is in communication with a compressor or air blower, for example. A silencer chamber inlet is in communication with an exhaust of the compressor or air blower, where an air flow is forced through the silencer and out a discharge port. The discharge port and the intake port are at opposing ends of the silencer. In addition, the silencer includes at least one baffle secured within the silencer chamber, where the baffle is configured to generate a non-directional interference with the air flow to assist in silencing the discharge.

Abstract: An intake silencer of a gas turbine capable of efficient noise reduction in which a high frequency sound-absorbing splitter group composed of a plurality of sound-absorbing splitters capable of reducing highfrequency component noise and a middle/low sound-absorbing splitter group composed of a plurality of sound-absorbing splitters capable of reducing middle/low frequency component noise are disposed separately in a gas flow direction. High frequency component noise is reduced by the high frequency sound-absorbing splitter group, and middle/low frequency component noise is reduced by the middle/low sound-absorbing splitter group.

Abstract: An acoustic panel is provided that includes at least one cellular core arranged between at least an internal skin and an external skin, wherein the external skin incorporates at least one fastener able to collaborate in a disconnectable fashion with a complementary fastener associated with a structure to which it is to be attached.

Abstract: A composite component such as a fan casing liner panel for a gas turbine engine comprises an abradable layer and a layer. The layer is provided with a septum layer, to which the abradable layer is bonded. The septum layer is perforated by holes, which enable air to be extracted from the region between the septum layer and the abradable layer during the process of bonding the components together, for example by a vacuum bonding process.

Abstract: A supercharger is provided, comprising a plurality of rotatable supercharger rotors each having a plurality of interleavable lobes configured to move air from an inlet to an outlet of the supercharger. Inner chambers in the lobes define an end opening and perforated end faces, at the end openings defining at least one port, having a length and a diameter. The at least one port is configured to operate with an associated air mass in the inner chamber to attenuate sound adjacent to the end opening.

Abstract: Some example muffling devices may include an inner flow conditioner shaped as a generally conical frustrum and a generally cylindrical an exhaust can around the inner flow conditioner. A ratio of a downstream end wall area of the inner flow conditioner to a downstream end annular area between the downstream end wall and the exhaust can may be about 0.12 to about 0.97. A ratio of the downstream end annular area to the downstream end wall area may be proportional, by a factor of about 0.8 to about 1.9, to a ratio of an effective area of the inner flow conditioner sidewall holes to an effective area of the inner flow conditioner downstream end wall holes. A ratio of a dissipation distance between the inner flow conditioner downstream end wall and the exhaust screen to the inner flow conditioner downstream end wall hole diameter may be greater than about 10.

Abstract: A one-piece soundproofing panel which is attached within an circumferential air blower casing of a turbomachine, with an axis, in which circulates an airflow from upstream to downstream, is disclosed. The panel includes a circumferential rigid seat with a longitudinal cylindrical part, arranged to axially extend with respect to the axis A of the turbomachine, having an outside surface, intended to come to extend facing with an internal surface of the air blower casing, and an internal surface to which is applied a soundproofing coating; and an annular fastening flange, formed at the upstream end of the longitudinal cylindrical part, radially outwardly extending, the fastening flange being arranged to cooperate with a fastening flange of the air blower casing.

Abstract: A method for assembling a turbine engine including a compressor is disclosed. The method includes coupling an inlet including an inertial particle separator (IPS) and a first surface that is defined using a segment angle, to a gas turbine engine, and coupling the first surface substantially flush against a fuselage of an aircraft to reduce drag.

Abstract: A propulsion system includes an engine with a fan and a nacelle that circumscribes the engine. The engine defines an axis. A distance between a forwardmost point at the top of the nacelle and at the front of the nacelle to a forwardmost point of the fan is greater than a distance between a forwardmost point at the bottom of the nacelle and at the front of the nacelle.

Abstract: An aircraft nacelle includes an air inlet (110) with a lip (114) extended to the back by a passage (116) to channel an air flow to a drive (112), the passage having at least one acoustic treatment panel (120) that includes, from the outside to the inside: an acoustically resistant porous layer (122); at least one cell-like structure (124), whose cells are sized for acoustic treatment; and a reflective or sealed layer (126). The reflective layer includes, near the end thereof that is oriented toward the lip, a surface (130) that is angled so as to be connected to the lip. A cell-like structure (136) is in contact with the angled surface, which forms an angle less than 30° with the tangent on the acoustically resistant layer. The cell-like structure is inserted between the angled surface of the reflective layer and an acoustically resistant porous layer.

Abstract: A gas turbine inlet system includes a main inlet portion, wherein an airflow is introduced to the gas turbine inlet system. Also included is a silencer assembly. The silencer assembly includes a first silencing panel, wherein the first silencing panel is oriented substantially perpendicularly to the airflow, and wherein the first silencing panel includes a first plurality of airflow apertures. The silencer assembly also includes a second silencing panel, wherein the second silencing panel is oriented substantially perpendicularly to the airflow, and wherein the second silencing panel includes a second plurality of airflow apertures.

Abstract: An inlet for an aircraft engine nacelle having an acoustic barrel panel, a septum buried or sandwiched within the acoustic barrel panel, and a perforated face sheet. The inlet may be located forward of an engine and/or an engine fan housed within the aircraft engine nacelle. Both the septum and the perforated face sheet may have perforations or holes therein of varying sizes and varying distances apart from each other. The smaller the area of the perforations or holes and the further apart they are from each other, the higher the impedance of a given area of the septum or the perforated face sheet. The impedance of the septum and/or the perforated face sheet may progressively increase in a direction away from the engine fan.

Abstract: Compact, high-pressure exhaust muffling devices are disclosed. Some example muffling devices may include an inner flow conditioner including an inlet configured to convey a pressurized fluid flow into an inner flow conditioner interior. The inner flow conditioner may include a plurality of inner flow conditioner holes. The muffling device may include an exhaust can disposed substantially around the inner flow conditioner and arranged to receive the pressurized fluid flow via the inner flow conditioner holes into an exhaust can interior. The exhaust can may include a plurality of exhaust screen holes arranged to discharge the pressurized fluid flow from the exhaust can interior. The exhaust can interior may be substantially devoid of flow obstructions between the plurality of inner flow conditioner holes and the exhaust screen holes.

Abstract: An acoustic treatment structure related to a leading edge onto which an aerodynamic stream flows, in particular at an air intake of an aircraft nacelle, includes—from the outside to the inside—at least one acoustically resistive substructure (30), at least one alveolar substructure including strips (32) of cells, arranged in a direction that is essentially perpendicular to the direction of flow of the aerodynamic stream, and at least one reflective layer (34). Each strip (32) includes a first part that insulates the strips from one another, called a support, with a U-shaped cross-section in the longitudinal direction, whose open surface that is opposite to the bottom of the U shape is flattened against the acoustically resistive substructure (30), and at least a second part, called partitioning, making it possible to partition the space that is delimited by the support and the acoustically resistive substructure (30) into cells.

Abstract: An aircraft nacelle includes an air inlet (110) with a lip (114) extended to the back by a passage (116) to channel an air flow to a drive (112), the passage having at least one acoustic treatment panel (120) that includes, from the outside to the inside: an acoustically resistant porous layer (122); at least one cell-like structure (124), whose cells are sized for acoustic treatment; and a reflective or sealed layer (126). The reflective layer includes, near the end thereof that is oriented toward the lip, a surface (130) that is angled so as to be connected to the lip. A cell-like structure (136) is in contact with the angled surface, which forms an angle less than 30° with the tangent on the acoustically resistant layer. The cell-like structure is inserted between the angled surface of the reflective layer and an acoustically resistant porous layer.

Abstract: A silencer includes a silencer inlet followed by a flow channel. The inlet can be attached to an outlet of a combustion chamber of a two-stroke engine. The flow channel at the channel end located opposite the silencer inlet leads into a first chamber where a second chamber is provided into which exhaust gas flows through a main outlet branched off the flow channel. The second chamber preferentially encloses the first chamber. The flow channel is flow-favourably moulded between the silencer inlet and the first chamber so that the exhaust gas flowing into the silencer inlet, because of its mass inertia, predominantly flows into the first chamber and, after filling the first chamber, flows back again in the direction towards the combustion chamber. The silencer allows a piston of the engine to include a piston skirt that is substantially designed closed.

Abstract: An inlet of a nacelle for channeling inlet airflow to a fan of a gas turbine engine includes a forward lip and an inner surface. The forward lip extends around a centerline axis of the engine and is adapted to accommodate a flow angle of incoming airflow. The inner surface extends from the forward lip along the centerline axis of the engine to adjacent the fan. The inner surface has a first profile above the centerline axis of the engine and a second profile below the centerline axis of the engine. The first profile and the second profile are adapted to define an inlet centerline axis that extends below the centerline axis of the engine at a face of the fan.

Abstract: A rotor windage noise damping system for an induction motor cooling vent A duct having a duct airflow path has a proximal end opening in communication with the cooling vent and the distal end opening is for communication with ambient air. The duct includes a plurality of baffles. The baffles are oriented in a generally parallel mutually spaced symmetrical or asymmetrical array relative to each other and the duct airflow path. Dimensions for baffle array symmetry or asymmetry, parallel spacing, baffle thickness and baffle inset from one of the duct openings are chosen to restrict distance between adjacent baffles to less than a wavelength of windage noise at selected propagation frequencies, yet provide for sufficient cooling airflow through the duct. The duct may be tuned to dampen selected propagation frequencies by changing the baffle array.

Abstract: A linear acoustic liner for an aircraft includes a cellular core having a first surface and an opposed second surface. A substantially imperforate back skin covers the first surface, and a perforate face skin covers the second surface of the core. The perforate face skin includes an outer face skin layer having a first plurality of spaced openings, an inner face skin layer having a second plurality of spaced openings, and a porous layer disposed between the outer face skin layer and the inner face skin layer. Each of the first plurality of spaced openings are substantially aligned with one of the second plurality of spaced openings.

Abstract: Wall partitioning between outside and inside of a room has an opening portion closed with a film. Sound insulating plate, comprising a lamination of a sound reflecting plate and a sound absorbing member, is supported in opposed relation to the opening portion and at an interval from the opening portion. Sound transmitted from outside of the room into the room through the film is reflected from the sound reflecting plate and then diffracted via sides of the interval, defined between the sound reflecting plate and the wall, to behind the reflecting plate to reach a human listener. Thus, with a mechanical construction, sound, propagated from outside the room into the room, can be made to be heard as sound of frequency characteristics desired by a human listener present in the room.

Abstract: The invention relates to a coating for acoustic treatment at the surface of an aircraft, in particular at the leading edge such as the air intake of an aircraft nacelle, said coating including an acoustically resistive layer (28), at least one cellular structure (30) and a reflective layer (32), characterized in that it comprises ducts (34) provided between said cellular structure (30) and the acoustically resistive structure (28), the ducts being each defined by a wall (36) separate from the walls of the cellular structure (30) and one end of the ducts being connected to a hot air supply.

Abstract: An air conditioner includes a cabinet configured to define an outer appearance of the air conditioner. The air conditioner also includes a front panel coupled to the cabinet and having an intake hole. The air conditioner further includes a fan assembly positioned within the cabinet and configured to guide a flow of air in the cabinet. The air conditioner further includes an intake panel configured to move to open or close the intake hole in response to a control signal. In addition, the air conditioner includes at least one noise reducing part positioned in the intake panel and configured to reduce a noise having at least one frequency bandwidth.

Abstract: A noise suppression characteristics adjustment method includes adjusting noise suppression characteristics of a noise suppressor, which includes a muffler having a reflection plate for reflecting sound from the cooling fan, the reflection plate being provided at a position in the cooling duct confronting an intake plane of the cooling fan and formed substantially parallel to the intake plane. A sound-absorbing part of the muffler is provided on the reflection plate. A distance d between the reflection plate and the intake plane is set such that d<c/(2×f) where f is a sound-absorption frequency of the muffler and c is a speed of sound. The muffler is located inside the cooling duct. A through-hole is provided in the reflection plate. The through hole includes a plurality of through-holes. A resonance frequency of the resonator sound absorber is adjusted by blocking at least one of the plurality of through-holes.

Abstract: Gaseous-fluid supply system for a general industrial power machinery application and a class of laboratory noise research and development comprises three subsystems, namely a gaseous-fluid delivery subsystem, a gaseous-fluid settling subsystem and a gaseous-fluid duct subsystem. Each subsystem must satisfy a set of fluid dynamic requirements determined by the situation in hand. For noise abatement application and research, an addition set of self-noise requirements must also be satisfied. An embodiment of a quiet air supply device for an aviation fan engine inlet noise abatement application using tangential blowing is also described. Acoustic treatment of the quiet air supply device is such that the self-noise of the supply air is low. The fluid dynamic quality of the supply air is such that the tangential blowing would not cause the aviation fan engine inlet noise source to increase.

Abstract: An inlet silencer for an air inlet in a housing, which housing contains a source of high frequency noise radiated by an air intake for the source of high frequency noise, comprises: a plenum that extends longitudinally within the housing that couples the air inlet in an upstream region of the plenum to the air intake for the source of high frequency noise in a downstream region of the plenum; a partition that extends laterally within the plenum between the upstream region of the plenum and the downstream region of the plenum; at least one channel that penetrates longitudinally through the partition that has a gap across its inner surface that approximates one wavelength of at least one fundamental frequency of high frequency noise that the source of high frequency noise generates; and acoustic damping material that lines the inner surface of the channel.

Abstract: The invention relates to a method for making an acoustic absorption panel in particular for the nacelle of an aircraft engine, the panel being of the type comprising a cellular core covered on one side with a so-called outer air-permissive skin and on the other side with a so-called inner perforated skin, the cellular core being formed by the edge-to-edge junction of a plurality of blocks with a cellular core (B1, B2). The method comprises the following steps: a) before the edge-to-edge junction of blocks with a cellular core (B1, B2), opening the cells (A1, A2) located on the edges of the blocks to be joined; and b) edge-to-edge dry joining the blocks (B1, B2) so that the open cells (A1, A2) engage into one another.

Abstract: An aircraft turbine engine with a takeoff fan speed and a landing fan speed, the aircraft engine includes a fan duct with a HQ (Herschel-Quincke) acoustic control noise reduction tube. The acoustic control noise reduction tube contains a movable frequency tuner obstruction. The movable frequency tuner obstruction is movable within the acoustic control noise reduction tube, with the movable frequency tuner obstruction movable along a fixed tube path length between a first takeoff frequency obstruction tube path location, and a second landing frequency obstruction tube path location, with the frequency tuner obstruction positioned at the first takeoff frequency location with the takeoff speed, and the frequency tuner obstruction positioned at the second landing frequency location with the landing speed to reduce noise.

Abstract: A method and system for an acoustic panel system are provided. The system includes a plurality of acoustic panel segments aligned circumferentially about an inner diameter of a fan containment case wherein each segment includes a radially inner surface defining a portion of a fluid duct, a radially outer surface defining a gap between the fan containment case and the acoustic panel segment, and an aft end lip configured to be inserted into a mating groove in the fan containment case. The system also includes at least one damping bumper coupled to the radially outer surface wherein the bumper extends from the radially outer surface to the fan containment case and comprises an energy absorbing elastomeric material configured to facilitate dissipating a forced response of a vibratory stimulus.

Abstract: The invention includes a joint assembly for connecting first and second longitudinal edges of portions of an acoustic barrel or panel having an open cell core, a perforated inner skin, and an outer skin. The joint assembly includes at least one strip covering a plurality of openings in walls of cells along the first and second longitudinal edges. The strip is separate from the inner and outer skins. A plate includes a first portion connected to the outer skin proximate to the first longitudinal edge, and a second portion connected to the outer skin proximate to the second longitudinal edge.

Abstract: An acoustically treated exhaust centerbody comprising a body including a body fore portion and a body aft portion. An internal passageway extends through the body in the axial direction. A resonator in the body fore portion includes a plurality of acoustic chambers. A plurality of ribs in the resonator form fore/aft walls of the acoustic chambers. Each rib is shaped substantially as a section of an annulus. A plurality of radial fins extend between adjacent ribs. The fins form sidewalls of the acoustic chambers. A skin overlies the acoustic chambers and forms an outer surface of the resonator.

Abstract: An acoustic assembly for a fan casing of a turbofan engine is made up from acoustic liner panel components which each comprise a body and a backing sheet. The body is an integral injection moulding that generally includes an acoustic structure, a perforated sheet and fastening portions. Adjacent panel components engage each other at non-linear circumferential edges which generally includes lugs on one of the components which are received in recesses of the other component. The lugs are defined by following cell walls over a convoluted path along the circumferential edge.

Abstract: An aero-acoustic aviation engine inlet with a single air blowing slot or multiple air blowing slots flows air over one or more segments of inlet acoustic lining surfaces at speeds that are higher than the inlet mean air flow speed, for aggressive inlet noise abatement.

Abstract: An air induction sound modification system for an internal combustion engine includes a multi-frequency sound suppression unit having Helmholtz resonators and a multi-component expansion chamber. A sound generator, which functions to radiate sound at a desirable, tuned frequency, extends between the multi-function sound suppression unit and a second expansion chamber, such as an air cleaner box.

Abstract: An acoustic panel includes a reflective layer, at least one alveolar structure, and an acoustically resistive structure forming an aerodynamic surface of an aircraft on the surface of which at least one acoustic wave propagates along an axis of propagation (24), whereby at least one of the characteristics of the acoustic panel influences the impedance of the panel that varies along the axis of propagation of the at least one acoustic wave, characterized in that it includes at least one first zone A with a constant acoustic impedance that is juxtaposed along the axis of propagation of the at least one acoustic wave at a zone C at which at least one characteristic of the acoustic panel that influences the impedance gradually varies along the axis of propagation of the at least one acoustic wave, whereby the characteristic has a value without sudden variations from one zone to the next.

Abstract: An acoustic treatment panel includes an acoustically resistive layer that defines a surface of an aircraft that is in contact with an aerodynamic stream, a reflective layer (50) between which are arranged at least one alveolar structure (52) with a number of cells dedicated to the acoustic treatment, and de-icing cavities (58) in which hot air circulates in contact with the acoustically resistive layer to ensure a frost treatment, characterized in that it includes holes for supplying de-icing cavities (58) with hot air and in that the capacity to treat the frost is adjusted along the zones by modifying the open surface ratio that results from the holes.

Abstract: A noise suppressor for an apparatus having a cooling fan and cooling duct includes a muffler including a reflection plate for reflecting sound from the cooling fan, the reflection plate being provided at a position in the cooling duct confronting the intake plane of the cooling fan and formed substantially parallel to the intake plane. A sound-absorbing part of the muffler is provided on the reflection plate, and a distance d between the reflection plate and the intake plane is set such that d<c/(2×f) where f is the sound-absorption frequency of the muffler and c is the speed of sound.

Abstract: A coating for acoustic treatment relative to an aircraft's surface, in particular a leading edge such as an air intake of an aircraft nacelle, includes an acoustically resistive layer, at least one alveolar structure (30), and a reflective layer. The alveolar structure (30) includes a number of tubes that empty out, on the one hand, at a first imaginary surface (34), and, on the other hand, at a second imaginary surface (36). The alveolar structure (30) includes cut-outs or openings (38) made at the side walls of certain tubes that make it possible to link adjacent tubes so as to create a network of communicating tubes that isolate at least one tube or a group of non-communicating tubes, whereby at least one of the communicating tubes is connected to at least one hot gas intake (40).

Abstract: A noise and vibration reduction system for an engine affixed to a body and a method for reducing vibrations in the body produced by that engine during operation. The present invention is particularly related to noise and vibration reduction in auxiliary power units installed on long-haul trucks and similar types of transportation vehicles. The primary noise and vibration reduction components of the present invention include an air intake silencer, a vibration tuner, and an engine speed limiter.

Abstract: An apparatus comprising includes a conduit portion having a conduit inner surface and a conduit outer surface, and a plurality of chambers in fluid communication with the conduit portion. The chambers include a first chamber defined, at least in part, by a first outer housing and a first chamber volume. The first chamber is in fluid communication with the conduit portion. A fluid is permitted to flow between the conduit portion and the first chamber through a first flow area. The chambers also include a second chamber defined, at least in part, by a second outer housing and a second chamber volume. The second chamber is in fluid communication with the conduit portion. A fluid is permitted to flow between the conduit portion and the second chamber through a second flow area. The first chamber volume is generally equal to the second chamber volume and the first flow area is greater than the second flow area.