Abstract: The invention relates to an aircraft turbofan type engine (1) comprising an air intake duct (2) having an inner face provided with an acoustic attenuation shroud (11) located upstream from a fan (3) of this engine (1). This acoustic attenuation shroud (11) comprises a regular alternation of first portions and second portions with different first and second thicknesses along the radial direction, the number of alternations being greater than twice the number of passing azimuth acoustic vibration modes occurring in the engine (1) without the acoustic attenuation shroud (11) operating under conditions corresponding to a landing phase and a take-off phase.

Abstract: An acoustic panel intended to be fixed internally to a fan casing of a turbojet engine, including an exterior face and an interior face which are curved about an axis, and two axially opposed transverse faces, the exterior curved face having at least one first recess on the side of a first transverse face and at least one second recess on the side of the opposite transverse face, said recesses each an attachment, in which said recesses do not open onto the interior curved face of the panel. Also covered are the turbojet engine including these panels and the method of mounting them.

Abstract: An inner wall for a nacelle of a turbomachine, the inner wall including an outer annular fan casing for surrounding the fan blades and including at its upstream end a flange for fastening to a ring in axial alignment therewith, and a soundproofing inner annular structure for extending upstream from the fan blades, the fan casing extending substantially as far as an upstream end of the soundproofing structure such that the upstream flange of the fan casing is situated in a vicinity of the upstream end of the soundproofing structure.

Abstract: The invention provides a device for acoustical treatment of the noise emitted by a bypass turbojet comprising a primary cowl having in an outer surface an inner annular acoustic treatment panel and a secondary cowl including in an inner surface an outer annular acoustic treatment panel arranged facing the inner panel. The inner and outer panels include respective central panel portions facing each other and extending axially over a common predetermined length, the length of the central panel portions lying in the range one-fifth to four-fifths of the total length of the panels, and the ratio between the acoustic resistances of the central panel portions being not less than 2.

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 multilayer acoustic treatment panel including a first cellular-structure core sandwiched between a perforated skin and an intermediate skin; and a second cellular-structure core sandwiched between the intermediate skin and a continuous skin. The perforated skin includes at least one pair of high-porosity zones presenting a perforation ratio greater than a perforation ratio of a remainder of the perforated skin and including an inlet zone and an outlet zone longitudinally spaced apart from each other, the high-porosity zones of a given pair communicating through the first cellular-structure core and the intermediate skin with the two ends of a soundwave flow channel arranged in the second cellular-structure core.

Abstract: One-piece soundproofing panel intended to be attached within an circumferential air blower casing of a turbomachine, comprising an axis, in which circulates an airflow from upstream to downstream, the panel including a circumferential rigid seat comprising a longitudinal cylindrical part, arranged to axially extend with respect to the axis A of the turbomachine, comprising 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: The invention provides a device for acoustical treatment of the noise emitted by a bypass turbojet comprising a primary cowl having in an outer surface an inner annular acoustic treatment panel and a secondary cowl including in an inner surface an outer annular acoustic treatment panel arranged facing the inner panel. The inner and outer panels include respective central panel portions facing each other and extending axially over a common predetermined length, the length of the central panel portions lying in the range one-fifth to four-fifths of the total length of the panels, and the ratio between the acoustic resistances of the central panel portions being not less than 2.

Abstract: An inner wall for a nacelle of a turbomachine, the inner wall including an outer annular fan casing for surrounding the fan blades and including at its upstream end a flange for fastening to a ring in axial alignment therewith, and a soundproofing inner annular structure for extending upstream from the fan blades, the fan casing extending substantially as far as an upstream end of the soundproofing structure such that the upstream flange of the fan casing is situated in a vicinity of the upstream end of the soundproofing structure.

Abstract: A device for attenuating acoustical noise from an exhaust nozzle of a turbojet is disclosed. The turbojet exhaust nozzle includes a central body defining the inner surface of the primary gas flow path. The central body includes an outer wall defining one, and only one, resonator cavity. The single resonator cavity is in fluid communication with the primary gas flow path via orifices through at least one upstream portion of the outer wall. The single resonator cavity and plurality of orifices compose a Helmholtz resonator.

Abstract: The present invention relates to a structural or non-structural turbojet engine fan casing connecting arm that also acts as a flow straightener downstream of the fan rotor. Its distinctive feature is that it is constructed to form an acoustic attenuator. In particular, it comprises a closed cavity and perforations on one of the faces so as to form a Helmholtz resonator. The arm forms part of the intermediate casing.

Abstract: The present invention relates to a structural or non-structural turbojet engine fan casing connecting arm (8B) that also acts as a flow straightener downstream of the fan rotor (3). Its distinctive feature is that it is constructed in such a way as to form an acoustic attenuator. In particular, it comprises a closed cavity and perforations (83) on one of the faces (8B in, 8Bex) so as to form a Helmholtz resonator. The arm forms part of the intermediate casing (8).

Abstract: The invention relates to a central body of a turbojet nozzle comprising a wall forming a cavity. The central body comprises a plurality of orifices pierced over at least one upstream portion of its wall and a single resonance cavity forming a Helmholtz resonator. Such a central body makes it possible to attenuate the low frequency noises.

Abstract: A soundproofing panel comprises a honeycomb core sandwiched between a solid skin and a porous skin, the cells of the honeycomb being divided in the direction of its thickness into at least two resonant cavities by a least one partition which is traversed by passages interlinking the cavities. The partitions are formed by a plurality of hollow microbeads having porous walls, the microbeads being bonded to one another and to the walls of the honeycomb at their points of contact. Such a soundproofing panel combines high performance in terms of linearity as a function of the level of sound excitation, attenuation band, bulk and mechanical strength.