The Bakerian Lecture, 1961 Sound generated aerodynamically

The author’s original theory of sound generated aerodynamically, that is, of sound radiation fields which are by-products of airflows, has been extended and improved by Curie and Ffowcs Williams. It is explained in this lecture fully but simply, and used as a framework for short analyses of our experimental knowledge on pulse-jet noise, hydrodynamic sound generation, aeolian tones, propeller noise, and boundary-layer noise, as well as for a somewhat extensive discussion of the noise of jets, both stationary and in flight. Improved knowledge of space-time correlations in turbulent flow is used to throw new light on the noise radiated by turbulent boundary layers, as well as by jets at the higher Mach numbers. Supersonic bangs and the scattering of both sound and shock waves by turbulence are briefly touched upon. The lecture ends with a discussion of the methods used for the reduction of jet aircraft noise, in the light of our knowledge of its physical basis.