High frequency excitation apparatus and method for reducing jet and cavity noise

Abstract

An active noise suppression apparatus and method for reducing jet engine noise and buffeting. A plurality of resonant cavities are formed in a structural member disposed on or adjacent to a jet engine exhaust nozzle. Each resonant cavity opens toward an output slot. A compressed air chamber is used to supply a pressurized, supersonic jetstream airflow through the inlet port into the interior area of the resonant cavity. This causes a high frequency, pulsed, excitation airstream to be generated outwardly from the cavity, out of the output slot and into the developing shear layer of the exhaust airflow. This high frequency, pulsed, excitation airstream induces modifications in the shear layer, which leads to a major reduction in the noise and buffeting generated by the developing shear layer. In an alternative embodiment, the resonant cavities are formed within one wall of a slot, where the slot is disposed along the leading edge of a cavity of the aircraft. The excitation airstreams cause a modification in the shear layer of the airflow over the cavity to significantly reduce the noise level and buffeting by the developing shear layer.