Abstract: An acoustic panel for an aircraft nacelle includes, from a central axis of the nacelle to the exterior thereof, a resistive skin perforated with sound-absorbing micro-perforations, a first attenuation stage, a septum perforated with holes, a second attenuation stage, and a back skin configured to provide the mechanical strength of the acoustic panel. The septum is a planar wall having a thickness greater than that of the resistive skin, preferably greater than 4 mm. Such a panel is configured to attenuate several frequency ranges one of which being a low-frequency range, while optimizing the weight, the cost and the air intake functions. The thickness of the septum, the dimensions of the holes in the septum, the OAR of the septum and the height of the second attenuation stage are adjusted to match the mean attenuated low frequency to the vibration frequency of the aircraft engine.

Abstract: A method for manufacturing a porous layer of an acoustic attenuation structure, porous layer of an acoustic attenuation structure thus obtained and acoustic attenuation structure comprising the porous layer. A method for manufacturing a porous layer of an acoustic attenuation structure includes a first step of production of a solid layer including at least one structural frame embedded in a resin matrix and having first and second reinforcing strips arranged so as to delimit zones without reinforcing strips and a second step of production of through-holes in the zones without reinforcing strips of the solid layer using a laser beam.

Abstract: An acoustic treatment panel includes at least one acoustically resistive layer, a reflective layer and at least one cellular structure interposed between the acoustically resistive layer and the reflective layer. The cellular structure includes cylindrical and identical main tubes which are closed at one end by the acoustically resistive layer and at the other end by the reflective layer, spacer zones between the main tubes, the spacer zones being sealed relative to one another, cutouts made at an end of certain main tubes, in contact with the reflective layer, and/or secondary tubes positioned in the main tubes and/or in the spacer zones, the cutouts and/or the secondary tubes being configured to generate acoustic cells of different dimensions from identical main tubes.

Abstract: An air intake structure for an aircraft nacelle is disclosed. The air intake structure delimits a channel and includes a lip having a U-shaped cross section oriented towards the rear, a first sound-absorbing panel fixed behind the lip and delimiting the channel, and a second sound-absorbing panel fixed behind the first sound-absorbing panel and delimiting the channel. Each sound-absorbing panel includes a cellular core which is fixed between an inner skin pierced with holes and oriented towards the channel, and an outer skin oriented in the opposite direction, where the inner skin of the first sound-absorbing panel has a thickness greater than the thickness of the inner skin of the second sound-absorbing panel, and where each of the inner skins includes a heat source which is embedded in the mass of the inner skin.

Abstract: An assembly constituting an acoustically absorbent material and including a first panel, a second panel pierced with holes, an intermediate panel pierced with through-holes and arranged between the first panel and the second panel, a first structure between the first panel and the intermediate panel and including first cages, a second structure between the second panel and the intermediate panel and including second cages, and for each through-hole of the intermediate panel, a tube opening out at the two ends thereof, where one of the ends of the tube is fixed to the intermediate panel at the through-hole, and where the other end of the tube is accommodated inside a first cage. Such an assembly makes it possible to obtain broad-band attenuation and is easy to manufacture.

Abstract: A cellular sound insulation structure and associated aircraft, a cell of which is provided with a diaphragm which includes a membrane having at least one orifice passing through a thickness of the membrane, and at least one tube surmounting the orifice and extending from a face of the membrane into one compartment of the cell, the tube comprising a free end, forming an acoustic outlet, which is positioned at a distance (p) from the base cross section of the cell. Also, a method for manufacturing such a cellular sound insulation structure, as well as to a tool for inserting a diaphragm into a cell. Such a cellular structure makes it possible to treat a wider acoustic frequency spectrum, and its acoustic dimensioning as well as its manufacture are simplified.

Abstract: An acoustic panel for an aircraft nacelle includes, from a central axis of the nacelle to the exterior thereof, a resistive skin perforated with sound-absorbing micro-perforations, a first attenuation stage, a septum perforated with holes, a second attenuation stage, and a back skin configured to provide the mechanical strength of the acoustic panel. The septum is a planar wall having a thickness greater than that of the resistive skin, preferably greater than 4 mm. Such a panel is configured to attenuate several frequency ranges one of which being a low-frequency range, while optimizing the weight, the cost and the air intake functions. The thickness of the septum, the dimensions of the holes in the septum, the OAR of the septum and the height of the second attenuation stage are adjusted to match the mean attenuated low frequency to the vibration frequency of the aircraft engine.

Abstract: An output cone of an aircraft propulsive assembly extending in a general direction called longitudinal direction and including a front part and a rear part. The longitudinal assembly of the front part and rear part forms an acoustic treatment system with at least two degrees of freedom. Such a system allows for the treatment of several frequency ranges or of one wide frequency range by the treatment of several overlapping ranges.

Abstract: An aft engine pylon fairing including a framework including lateral panels, transverse reinforcing ribs, and a heat shield linked to the framework. The heat shield has a multilayer structure comprising an insulating core configured both to constitute a thermal barrier and to damp acoustic waves, an outer skin configured to guide an aerodynamic flow and contribute to the acoustic damping, and an inner skin configured to ensure the mechanical strength of the shield. The shield multilayer structure allows the aft engine pylon fairing to contribute to the attenuation of the noise nuisances of the engine, and, also, to improve the thermal insulation conferred by the shield by allowing the use, for the insulating core of the shield, of materials having a better thermal resistance but a low mechanical rigidity, the mechanical strength being essentially ensured by the inner skin of the multilayer structure.

Abstract: A double-enclosure acoustic element of small size, in particular for an aircraft acoustic panel. The acoustic element has a first enclosure with a mouth and a second enclosure with, at a front longitudinal end, a mouth and arranged inside the first enclosure, these first and second enclosures being joined together at the front. The acoustic element includes a slotting assembly system, the assembly system including at least one protruding element on the first edge of one of the first and second enclosures and at least one recess in the first edge of the other of the first and second enclosures, the protruding element and the recess having complementary shapes such that the protruding element can be slotted into the recess. Thus, the two enclosures can be assembled by quick and easy slotting.

Abstract: A method for manufacturing a porous layer of an acoustic attenuation structure, porous layer of an acoustic attenuation structure thus obtained and acoustic attenuation structure comprising the porous layer. A method for manufacturing a porous layer of an acoustic attenuation structure includes a first step of production of a solid layer including at least one structural frame embedded in a resin matrix and having first and second reinforcing strips arranged so as to delimit zones without reinforcing strips and a second step of production of through-holes in the zones without reinforcing strips of the solid layer using a laser beam.

Abstract: An assembly constituting an acoustically absorbent material and including a first panel, a second panel pierced with holes, an intermediate panel pierced with through-holes and arranged between the first panel and the second panel, a first structure between the first panel and the intermediate panel and including first cages, a second structure between the second panel and the intermediate panel and including second cages, and for each through-hole of the intermediate panel, a tube opening out at the two ends thereof, where one of the ends of the tube is fixed to the intermediate panel at the through-hole, and where the other end of the tube is accommodated inside a first cage. Such an assembly makes it possible to obtain broad-band attenuation and is easy to manufacture.

Abstract: An air intake structure for an aircraft nacelle is disclosed. The air intake structure delimits a channel and includes a lip having a U-shaped cross section oriented towards the rear, a first sound-absorbing panel fixed behind the lip and delimiting the channel, and a second sound-absorbing panel fixed behind the first sound-absorbing panel and delimiting the channel. Each sound-absorbing panel includes a cellular core which is fixed between an inner skin pierced with holes and oriented towards the channel, and an outer skin oriented in the opposite direction, where the inner skin of the first sound-absorbing panel has a thickness greater than the thickness of the inner skin of the second sound-absorbing panel, and where each of the inner skins includes a heat source which is embedded in the mass of the inner skin.

Abstract: A method for obtaining a porous acoustic layer, comprising a step of deposition of a plurality of fiber wicks arranged in at least two secant directions, the width, the orientation and/or the spacing of the fiber wicks being determined as a function of the open surface ratio desired for each zone of the porous acoustic layer. A porous acoustic layer obtained according to the method, as well as an acoustic panel comprising at least one porous layer, are also disclosed.

Abstract: An acoustic treatment device for an internal primary ejection duct from a turbojet pod, including an upstream zone and a downstream zone relative to an airflow direction in the primary ejection duct, the upstream and downstream zones being located on each side of a separating wall with a first face on the side of the upstream side and a second face on the side of the downstream side. The separating wall is a micro-porous wall and the face of the separating wall located on the side of the downstream side is covered by a honeycomb structure to attenuate high frequency acoustic waves. Such a device may find application to treatment of combustion and turbine noises.

Abstract: An acoustic treatment device for an internal primary ejection duct from a turbojet pod, including an upstream zone and a downstream zone relative to an airflow direction in the primary ejection duct, the upstream and downstream zones being located on each side of a separating wall with a first face on the side of the upstream side and a second face on the side of the downstream side. The separating wall is a micro-porous wall and the face of the separating wall located on the side of the downstream side is covered by a honeycomb structure to attenuate high frequency acoustic waves. Such a device may find application to treatment of combustion and turbine noises.