In this paper, we review known characteristics of rocket noise. These include low peak frequencies, a high radiation efficiency and a large angle of peak directivity relative to that of subsonic and supersonic jets. The extended source region and high temperatures in a rocket plume are discussed. Evidence is presented to support the contention that it is Mach wave radiation from the transonic region of the plume that governs the sound power. We summarize properties of noise measured in the far-field during rocket launches. This high intensity noise is rich in shocks and the time domain data are positively skewed. Far-field noise spectra do not decrease with distance as would be expected on the basis of linear absorption theory. We briefly discuss signal processing techniques that have the potential to better distinguish the unique properties of rocket noise and we explore the idea of using non-linear acoustic propagation codes to better understand these properties. We conclude by soliciting input on the best way to proceed in these research efforts.

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