Abstract: An aircraft auxiliary power unit sound attenuation apparatus includes a perforated body having a center aperture through which exhaust fluid passes, a backing member outwardly offset from the perforated body, a plurality of connecting members coupling the perforated body to the backing member to form a locally reacting sound attenuation member having a plurality of channels spanning outwardly from the perforated body to the backing member, and a bulk absorber disposed in each of the plurality of channels where the bulk absorber is in fluid communication with the exhaust fluid, where the locally reacting sound attenuation member is in fluid communication with an auxiliary power unit of an aircraft so that the plurality of channels are oriented in a direction crossing a pressure drop direction of an exhaust fluid flow passing through the center aperture and each channel circumscribes the center aperture.

Abstract: An aircraft engine sound attenuation apparatus includes a perforated face member, a backing member, a plurality of connecting members coupling the perforated face member to the backing member to form a plurality of channels spanning from the perforated face member to the backing member, and a bulk absorber disposed in each of the plurality of channels, wherein the plurality of channels are connected to an interior portion of an aircraft engine nacelle component so that the plurality of channels are oriented in a direction substantially normal to a direction of fluid flow pressure drop passing through the aircraft engine.

Abstract: An aircraft auxiliary power unit sound attenuation apparatus includes a perforated body having a center aperture through which exhaust fluid passes, a backing member outwardly offset from the perforated body, a plurality of connecting members coupling the perforated body to the backing member to form a locally reacting sound attenuation member having a plurality of channels spanning outwardly from the perforated body to the backing member, and a bulk absorber disposed in each of the plurality of channels where the bulk absorber is in fluid communication with the exhaust fluid, where the locally reacting sound attenuation member is in fluid communication with an auxiliary power unit of an aircraft so that the plurality of channels are oriented in a direction crossing a pressure drop direction of an exhaust fluid flow passing through the center aperture and each channel circumscribes the center aperture.

Abstract: An aircraft auxiliary power unit sound attenuation apparatus includes a perforated body having a center aperture through which exhaust fluid passes, a backing member outwardly offset from the perforated body, a plurality of connecting members coupling the perforated body to the backing member to form a locally reacting sound attenuation member having a plurality of channels spanning outwardly from the perforated body to the backing member, and a bulk absorber disposed in each of the plurality of channels where the bulk absorber is in fluid communication with the exhaust fluid, where the locally reacting sound attenuation member is in fluid communication with an auxiliary power unit of an aircraft so that the plurality of channels are oriented in a direction crossing a pressure drop direction of an exhaust fluid flow passing through the center aperture and each channel circumscribes the center aperture.

Abstract: An aircraft auxiliary power unit sound attenuation apparatus includes a perforated body having a center aperture through which exhaust fluid passes, a backing member outwardly offset from the perforated body, a plurality of connecting members coupling the perforated body to the backing member to form a locally reacting sound attenuation member having a plurality of channels spanning outwardly from the perforated body to the backing member, and a bulk absorber disposed in each of the plurality of channels where the bulk absorber is in fluid communication with the exhaust fluid, where the locally reacting sound attenuation member is in fluid communication with an auxiliary power unit of an aircraft so that the plurality of channels are oriented in a direction crossing a pressure drop direction of an exhaust fluid flow passing through the center aperture and each channel circumscribes the center aperture.

Abstract: An aircraft engine sound attenuation apparatus includes a perforated face member, a backing member, a plurality of connecting members coupling the perforated face member to the backing member to form a plurality of channels spanning from the perforated face member to the backing member, and a bulk absorber disposed in each of the plurality of channels, wherein the plurality of channels are connected to an interior portion of an aircraft engine nacelle component so that the plurality of channels are oriented in a direction substantially normal to a direction of fluid flow pressure drop passing through the aircraft engine.