The rest of this paper is as follows.In Section 2, an analysis of the F-22 A aircraft noise data is presented . It will be shown that as the rate of engine fuel burn increases, a new noise component emerges in the noise data .At afterburner condition, the new noise component is dominant over the angular sector from θ¼1101 to 1301 and for frequencies above 200 Hz. In Section 3, a plausible generation mechanism for the new noise component is proposed . Because of the scarcity of available data, a definitive confirmation is not possible at this time .Forth is reason ,it is important to regard the proposed mechanism as merely a likely mechanism .It is believed that the new noise component is combustion related .Unlike laboratory jet mixing noise, the proposed noise component is generated inside the nozzle of the jet and not in the jet plume .Results of numerical simulations will be presented to demonstrate that the passage of hot spots (entropy waves) through a military-style nozzle can, indeed ,lead to the generation of intense noise. This is generally referred to as indirect combustion noise.
Here, it is proposed as the source of the new noise component. In the absence of measured flow and temperature fluctuation data, numerical simulation results are the best we can offer to support the proposed noise mechanism. Section 4
summarizes thefindingsofthisinvestigation.Conclusionsareprovided.