Patent ID: 9587563
Date: 2017-03-07
CPC Classifications: B64C,B64D,F01N,F02C,F02K,F05D,G10K

Claim:
1. An aircraft auxiliary power unit sound attenuation apparatus comprising: 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; at least one septum layer disposed between the perforated body and backing member where the at least one septum layer divides each channel into at least two portions; and a bulk absorber disposed in each of the plurality of channels where the bulk absorber is in fluid communication with the exhaust fluid; wherein 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.