Concerning the Noise of Turbulent Jets

The suggestion that the noise generators of turbulent jets undergo convection effects which are limited in such a way as to follow a similarity behavior leads directly to a resolution of Lighthill's paradox, namely, the problem of accounting for the noise power depending upon the eighth power of the jet velocity simultaneously with the gross directional bias. This hypothesis shown to be at least plausible to a first approximation owing to the general velocity field of the jet having typical dimensions comparable to a fraction of a wavelength; an important corollary is the expectation of appreciable refraction effects. Aspects relevant to the directional peaks of the higher frequencies being less pronounced and located further from the jet axis, and of the slow frequency rise, are briefly discussed.