摘要:
An assembly useful in reducing aircraft engine noise such as turbofan engine noise comprises: (a) a core portion comprising at least one entrance end and at least one exit end for the passage of acoustic energy therethrough; (b) a first member having an exterior face and an interior face, wherein the first member is adjacent to at least a part of the core portion, and the first member has a plurality of openings therein to permit the passage of acoustic energy therethrough; and (c) a second member having an exterior face and an interior face, wherein the interior face of the second member is adjacent to the core portion. The core portion may be a honeycomb acoustic structure, and the first member may be perforated to permit the passage of acoustic energy into and out of the conduit portion.
摘要:
Reduction or cancellation of acoustic noise is achieved by providing an amplified, oppositely phased version of the noise by means of an acousto-fluidic amplifier. The amplified acoustic output noise is delivered through an impedance matching horn in destructively interfering relation with the original noise. Depending on the acoustic noise source and its spatial distribution, the acousto-fluidic amplifier may be a single stage amplifier or multiple stages connected in parallel and/or cascade, with output horns spatially distributed to have the maximum cancellation effect. Sensed noise, prior to fluidic amplification, may be processed in a manner to effect feedback or feedforward control of the amplified acoustic output signals.
摘要:
An array of adaptive or fixed Herschel-Quincke tubes aligned in a circumferential or helical array about an inlet of a turbofan engine. The array of tubes effectively divide the acoustic energy generated by the engine. One of the energy components propagates within the tubes while the other propagates within the engine compartment. At some time certain, the acoustic energy in the tubes is reintroduced into the engine compartment to cancel the acoustic energy remaining in the engine as it propagates from the fan towards the inlet and outlet openings.
摘要:
An active vibration absorber including a frame connected to a structure to be controlled and at least two reaction mass elements operatively connected to the frame. Each of the reaction mass elements is independently movable with respect to said frame. The absorber includes a force generating member for controlling relative movement between the reaction mass elements for damping vibration of the structure. The inventive dual reactive mass absorber requires less control force to produce the same vibration attenuation as conventional single reactive mass absorbers.