An aircraft landing gear bay door 140 including an attachment mechanism suitable for pivotally mounting the door to an aircraft, a first side 141 arranged to face inwardly in relation to the aircraft landing gear bay when the door is closed and face towards one side of a main leg of the landing gear when the door is open and the landing gear is deployed, and a second opposite side 142. The shape formed from the first and second sides provides an aerofoil profile of the door. The invention also provides an aircraft landing gear arrangement 100, an aircraft 1000, methods of operating an aircraft and a method of reducing noise.

A noise attenuation panel for a structure within a propulsion system includes a first plurality of unit cells; and a second plurality of unit cells, the second plurality of unit cells merged within the first plurality of unit cells, the first plurality of unit cells including a first periodic structure having a first unit cell, a second unit cell, a third unit cell and a fourth unit cell, each of the first unit cell, the second unit cell, the third unit cell and the fourth unit cell including a central body interconnected via a plurality of lateral tubes extending from the central body, the first periodic structure forming a first lateral layer of unit cells.

A muffler assembly for an exhaust system is in fluid communication with a collector via an exhaust conduit. The muffler assembly includes a primary pipe, a valve, a secondary pipe, a tuner tube and a bleed port. The primary pipe extends through an enclosed volume of the muffler. The valve is operable to restrict flow through the primary pipe. When a standing wave is present, a resonance length is defined by a length of the exhaust system that extends from the collector to the valve. The tuner tube includes an open tuner tube end in fluid communication with the primary pipe and a closed tuner tube end. The tuner tube has a tuner tube length that is substantially one-quarter of the resonance length. The bleed port is formed in the primary pipe, allowing fluid communication with the enclosed volume, and positioned downstream from open tuner tube end.

A noise suppressor is removably installed in power generator equipment including an enclosure and a power generator unit. The enclosure includes at least one of an air intake port and an air discharge port that are vents. The power generator unit is covered with the enclosure. The noise suppressor includes a tubular member having a first opening that opens to a direction different from the vent and a second opening that opens to the vent, forming a channel for gas leading from the first opening to the second opening, and provided with an acoustic liner inside the channel. The tubular member has such a shape that the channel bends at a plurality of points.

An apparatus and method are provided for a drone elimination muffler to attenuate drone exhibited by engine exhaust systems. The drone elimination muffler comprises a hollow canister having a length and a diameter, and a tuned port comprising a first end connected to the canister and a second end connected to the exhaust system. The canister operates in concert with the tuned port as a dampener configured to substantially attenuate exhaust drone, or resonance, at one or more frequencies of engine operation. A valve is configured to switch the drone elimination muffler between a closed state in which the exhaust system operates without acoustic influence due to the drone elimination muffler, and an open state in which the drone elimination muffler directly influences the acoustic properties of the exhaust system.

Described herein are noise-resistant assemblies pursuant to various commercial and industrial applications. The noise-resistant assemblies can include duct assemblies, pool assemblies, motor assemblies, carpet flooring assemblies, and roofing assemblies. These assemblies incorporate an acoustic article containing a porous layer and a heterogeneous filler having a median particle size of from 1 micrometer to 1000 micrometers and a specific surface area of from 0.1 m.sup.2/g to 10,000 m.sup.2/g received in the porous layer.

A system and method for bonding together a facesheet and an acoustic screen of an acoustic liner using a solid adhesive film having a first adhesive side opposite a second adhesive side are provided. The system includes a solid adhesive film having a first adhesive side opposite a second adhesive side; an acoustic screen bonded to the first adhesive side of the solid adhesive film; and a facesheet bonded to the second adhesive side of the solid adhesive film. The method includes bonding the facesheet to the first adhesive side of the solid adhesive film and bonding the acoustic screen to the second adhesive side of the solid adhesive film.

An oxygen pressure relief and ventilation system includes a flow fuse fluidly coupled downstream of a pressure regulator. The pressure regulator is operatively coupled to an oxygen tank, and the oxygen tank is located in an unpressurized compartment of an aircraft. A pressure relief valve is fluidly coupled downstream of the flow fuse. A ventilation pathway fluidly couples the unpressurized compartment with a pressurized compartment. The flow fuse and the pressure relief valve are configured to cooperatively mitigate downstream flow of pressurized oxygen if the pressure regulator fails. The ventilation pathway is configured to allow air from the pressurized compartment to pass through to the unpressurized compartment for diluting a concentrated oxygen in the unpressurized compartment.

A system configured to thermally regulate heat dissipation of a power plant system (e.g. steam turbine, gas turbine compressor, intercooler or other fluidic thermal source, etc.) and acoustically attenuate operation of an air cooled heat exchanger via sound reflection, sound absorption, sound diffraction, and/or active noise cancellation is disclosed. In one embodiment, a system includes: a set of inner barriers; a base barrier disposed beneath the set of inner barriers; a set of outer barriers disposed about the base barrier and the set of inner barriers, the set of outer barriers including a top surface located above a bottom surface of the set of inner barriers; a heat exchanger fluidly connected to a power generation system and disposed within the set of inner barriers; and a set of fans disposed within the set of inner barriers and configured to form a flow of air through the set of inner barriers.

A muffler includes an exhaust pipe, a shell, and a cover. The exhaust pipe includes communication holes and is configured to allow an exhaust gas to flow through an interior of the exhaust pipe. The shell is disposed outside the communication holes to cover the communication holes. The cover has a tubular shape. The cover is disposed between the exhaust pipe and the shell. The cover is disposed at a distance, which is specified in advance, from the exhaust pipe.