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Far field noise data were taken for convergent nozzles of various shapes and sizes at subsonic velocities exceeding 400 feet per second. For a circular nozzle, the nozzle inlet shape and lip thickness had no effect on the noise level, directivity, or spectra when compared at the same nozzle exit diameter and peak exhaust velocity. A sharp edged orifice was one exception to this statement. Coannular nozzles can produce additional high frequency noise. Blunt ended centerbodies, where there is significant base drag, also generate significant additional noise.The total noise power generation was essentially the same for cirpular, slot, and plug nozzles of good aerodynamic shape. The noise radiation patterns were essentially the same for these nozzle shapes except°° near the nozzle exhaust axis. These patterns were well described by "7 '(1 -M C cos 9j)~3, except near the nozzle exhaust axis. w

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Free field pure jet noise data were taken for a large range of coaxial nozzle configurations. The core nozzles were circular (1 to 4 in. diam.) and plug types. The fan to core area ratio varied from 0.7 to 43.5, while the velocity ratio typically varied from 0 to 1. For most cases the two nozzles were coplanar but large axial extensions of either nozzle were also tested. Correlation of the data resulted-in a simple procedure for estimating ambient temperature subsonic coaxial jet noise spectra over a wide range of geometric and flow parameters.