Systems and devices of the various embodiments may provide a low-drag, variable-depth acoustic liner having shared inlet volumes. Various embodiments may include a low-drag, variable-depth acoustic liner providing aircraft noise reduction. Acoustic liners according to the various embodiments may be used in engine nacelles and/or on external surfaces of an aircraft to reduce acoustic radiation. Acoustic liners according to various embodiments may provide increased broadband acoustic performance with less drag than conventional liners. Various embodiments may provide an acoustic liner with a reduced open area of the facesheet, and therefore reduced drag of the liner, when compared with conventional acoustic liners.

A sound isolating wall assembly includes a plurality of walls defining a space between the plurality of walls. At least one acoustic scatterer is disposed within the space between the plurality of walls. The at least one acoustic scatterer has an opening and at least one channel. The at least one channel has a channel open end and a channel terminal end, with the channel open end being in fluid communication with the opening.

Embodiments of the present technology are directed to air treatment reactor modules, and associated systems and devices. An exemplary reactor module can include a housing, an ultraviolet (UV) light source disposed within the housing, and a plurality of hollow elongate conduits disposed within the housing and peripheral to the UV light source. The UV light source and individual conduits can extend in a lateral direction perpendicular to the direction of air flow through the reactor module. The conduits can include a plurality of holes and be at least partially coated with a photocatalytic material. The housing can have an inner surface comprising a reflective material that, in operation, reflects UV light emitted from the UV light source.

A sound isolating wall assembly includes a plurality of walls defining a space between the plurality of walls. At least one acoustic scatterer is disposed within the space between the plurality of walls. The at least one acoustic scatterer has an opening and at least one channel. The at least one channel has a channel open end and a channel terminal end, with the channel open end being in fluid communication with the opening.

An apparatus for reducing sound levels in an HVAC system, the apparatus including a housing configured to be positioned within an air inlet vent for an HVAC system. The housing includes a first opening configured to intake air and a second opening configured to out put air and a plurality of baffles positioned within said housing, each baffle including a body defining a volume and has a plurality of perforations, wherein each baffle is affixed to the housing and wherein the plurality of perforations are configured to allow airflow through the volume of the body and redirecting sound waves.

Aspects of the present disclosure include a casing comprising an air inlet and an air outlet, a fan configured to move air from the air inlet to the air outlet, and a tunable sound attenuating module having an opening at a first end of the tunable sound attenuating module, a cavity, and a back wall at a second end of the tunable sound attenuating module, wherein: the tunable sound attenuating module is oriented such that the back wall is closer to the fan than the opening, and a length of tunable sound attenuating module is substantially one fourth of the acoustic wavelength of a sound generated by the fan.

Provided are conduits for air flow that are capable of reducing noise and related methods. The provided conduits include a first section that is tubular and substantially non-perforated and a second section with at least a portion having a multiplicity of microperforations that provide an average flow resistance of from 50 MKS Rayls to 8000 MKS Rayls therethrough. The second section is either (a) tubular and connected in series with the first section, with an outer surface of the second section being in fluid communication with an outer surface of the conduit, or (b) disposed within the first section.

Embodiments of the present technology are directed to air treatment reactor modules, and associated systems and devices. An exemplary reactor module can include a housing, an ultraviolet (UV) light source disposed within the housing, and a plurality of hollow elongate conduits disposed within the housing and peripheral to the UV light source. The UV light source and individual conduits can extend in a lateral direction perpendicular to the direction of air flow through the reactor module. The conduits can include a plurality of holes and be at least partially coated with a photocatalytic material. The housing can have an inner surface comprising a reflective material that, in operation, reflects UV light emitted from the UV light source.

An object is to provide a silencing system that includes a silencer disposed in a ventilation sleeve, can suppress the generation of negative pressure in the interior, and can prevent a door or the like of an interior entrance from being difficult to open. The silencing system includes one or more silencers that are disposed in a ventilation sleeve provided to penetrate a wall separating two spaces, and “αA>10.sup.C−(0.1/P)×TL” is satisfied in a case where a gap equivalent area of the ventilation sleeve in which the silencer is installed is denoted by αA and a normalized sound transmission loss in an octave band in which a first resonant frequency of the ventilation sleeve is present is denoted by TL. C denotes a constant determined by a measurement system in a case where there is no silencer and P denotes a transmission efficiency coefficient.

A noise suppression apparatus for an air handling unit includes an inlet section connectable to a fan of the air handling unit. The inlet section includes a forward wall spaced apart from an aft wall to define an internal chamber, and an inlet wall extending between the forward wall and the aft wall, the inlet wall defining an inlet air opening. A plurality of internal walls in the inlet wall define a plurality of resonator openings that each open to at least one of a plurality of resonator sections within the internal chamber. The plurality of resonator sections include at least one quarter wave tube section and at least one Helmholtz resonator section. One or more resonator sections are configured to attenuate noise generated by the fan at two or more frequencies. At least one resonator opening of the plurality of resonator openings opens to a plurality of resonator sections.