A system for reducing jet noise emission from an internally mixed gas
turbine engine exhaust, comprising a fan/core flow mixer having a
plurality of mixer lobes and a common flow nozzle having an equal number
of tabs located along a circumferential edge of an aft end of the nozzle.
There is a predetermined clocking relationship between the plurality of
mixer lobes and the plurality of nozzle tabs that results in reduced
exhaust noise emission, most evident in the lower frequency range. A
method for reducing jet noise emission from an internally mixed gas
turbine engine exhaust comprises selectively aligning a circumferential
distribution of a mixed flow vorticity field produced by a fan/core mixer
with a circumferentially distributed exhaust flow vorticity field
produced by a modified common flow nozzle at an exit plane of the engine
exhaust.