Abstract: An apparatus for suppressing or attenuating acoustic pressure oscillations in a gas turbine engine combustor, the apparatus having a quarter wave resonator with a cavity closed at a first end and open at a second end and a characteristic length that reflects waves 180 degrees out of phase with the incoming waves and a viscous damper at the open end of the cavity. At least one resonating tube with a closed end and an open end and a single cavity therebetween, a damping plate with a plurality of apertures therethrough disposed across the open end, and a means for mounting the tube on the engine so that the damping plate is essentially flush with the wall. The apertures preferably have a total open area that is about 8% of an inclusive area of the open end and the tube may be cylindrical and the apertures circular.

Abstract: An acoustic suppression panel is provided with a perforated plate covering a layer of a bulk absorber. A flexible, fluid-impervious membrane is placed between the plate and the bulk absorber, and supported in a manner so as to permit the membrane to become essentially acoustically transparent. An acoustically hard backing plate is disposed adjacent the bulk absorber, the backing plate being provided with perforations to allow pressure equalization for flight applications. A facing sheet of sintered metal covers the perforated plate to provide an aerodynamically continuous flow surface for the plate which is highly resistant to foreign object impact.

Abstract: A phased treatment noise suppression panel is provided for use in an exhaust duct. The panel consists of individual sections designed with specific modal attenuation characteristics and located axially within the duct in such a sequential order, with respect to the noise source, as to take maximum advantage of modal redistribution effects on overall noise suppression.