Correlation and prediction of jet noise

Measurements of subsonic jet noise made on a model jet rig in the anechoic chamber ofthe National Gas Turbine Establishment are presented. Jet noise spectra for three nozzles of diameters 2·84, 2·4 and 1·52 inches have been obtained. Considerable care has been taken to ensure that unwanted noise from sources such as valves and ducting upstream of the nozzle are insignificant compared with the jet mixing noise. Attempts have then been made to collapse all the data points obtained on to one curveThis is done first of all by normalizing the 1/3 octave and overall sound pressure levels for the theoretical parameters obtained from Lighthill's theory. Empirical schemes are then presented to collapse the data for all the angles and the frequencies. The prediction schemes for 1/3 octave SPL, PWL and OASPL and OAPWL are considered. The schemes presented predict noise accurately for cold and clean jets.