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

An apparatus for reducing noise from a jet engine exhaust, comprising:

• a plurality of resonant cavities formed in a first member and disposed adjacent an exhaust nozzle of said jet engine;
• a plurality of ports formed in a second member for forming supersonic jetstream airflows;
• each of said resonant cavities being aligned with an associated one of said jetstream airflows;
• wherein said jetstream airflow entering said inlet port of each said resonant cavity causes an oscillating excitation airstream to flow from said interior area of each said resonant cavity outwardly into a developing shear layer of exhaust airflow exiting from said exhaust nozzle;
• and
• whereby said oscillating excitation airstream has a frequency of at least about 2500 Hz and induces modifications into said developing shear layer to thus reduce noise and buffeting caused by said shear layer.

An apparatus for reducing noise from a jet engine exhaust, comprising:

• a slot formed adjacent to a leading edge of a cavity of an aircraft;
• a plurality of spaced apart input ports opening on a first wall of said slot for forming supersonic jet airstreams each being directed across said slot;
• a corresponding plurality of resonant cavities formed so as to each open onto a second wall of said slot, and each said resonant cavity being aligned with an associated one of said airstreams to receive its associated said airstream, wherein each said airstream causes a high frequency, pulsed excitation airstream to be generated outwardly from its associated said resonant cavity into and then outwardly of said slot;
• and
• whereby said high frequency, pulsed, excitation airstreams operate to modify a shear layer of airflow at said leading edge of said cavity to thereby reduce noise and buffeting at said leading edge of said cavity.

A method for reducing noise and buffeting from a developing shear layer near a cavity of an aircraft during flight of the aircraft, said method comprising the steps of:

• forming a slot in a panel of said aircraft adjacent to a leading edge of said cavity;
• forming a plurality of spaced apart ports in a first wall of said slot for directing a plurality of supersonic jets of airflow into said slot;
• forming a plurality of spaced apart resonant cavities in a second wall of said slot, each of said resonant cavities being in alignment with a respective one of said ports for receiving said supersonic jets of airflow;
• and
• whereby said resonant cavities receive said jets of airflow and cause high frequency, pulsed, excitation airstreams to be generated which are directed into and outwardly of said slot, said airstreams operating to modify said developing shear layer to reduce noise and buffeting at said cavity.