An improved method for predicting the effects of flight on jet mixing noise

An improvement to the NASA method (1976) for predicting the effects of flight on jet mixing noise has been developed. The earlier method has been shown to agree reasonably well with experimental flight data for jet velocities up to about 520 m/s (∼1700 ft/s). The poorer agreement at high jet velocities appeared to be due primarily to the manner in which supersonic convection effects were formulated. The purely empirical supersonic convection formulation of the earlier method has now been replaced by one based on theoretical considerations. Other improvements of an empirical nature have been included based on model‐jet/free‐jet simulated flight tests. This report presents the new prediction method and comparisons with experimental data obtained from the Bertin Aerotrain with a J85 engine, the DC‐10 airplane with JT9D engines, and the DC‐9 airplane with refanned JT8D engines. It is shown that the new method agrees better with the data base than either the earlier NASA method or a recently proposed SAE method.