Measurements of the distribution of sound source intensities in turbulent jets.

The spatial distribution of sound source intensities in jets is determined from the sound radiated into the acoustic far field by means of a concave mirror-microphone system. The mirror forms an image of the sound sources in a region far enough from the jet so that near field pressure fluctuations can be neglected. The sound intensity in the image is thus closely related to the strength of the actual sound sources in the jet. Results of measurements with jets of Mach numbers 0.7 to 1.9 emanating from circular nozzles and from slot nozzle-flap combinations demonstrate the influence of Mach number and of other parameters upon the sound source distribution.