ESDU 89041 gives a graphical method for estimating overall and one-third octave band sound pressure levels as a function of observer distance and angle to the efflux plane, jet pipe diameter, and jet temperature and velocity. The data are also given in 10 tables, each for a fixed angle for the observer to the exhaust plane from 30 to 120 degrees in 10 degree intervals. The method is derived by correlating experimental data from model tests in which all sources of noise other than that due to pure jet mixing have been eliminated. Atmospheric absorption and ground reflection effects are excluded. ESDU 98019 complements the method by providing a means for interpolating in or extrapolating any jet noise experimental data; it includes databases, one of which is that used here, and the user can replace or supplement that database as appropriate.