The Evolution of the Engine Noise Problem: An examination of the sources of engine noise and of the design concepts adopted to alleviate the problem

DURING the 1950s noise around airports increased steadily with increasing traffic and size of aircraft. With the introduction of heavy jet transports the very different quality of noise (compared to piston engines) highlighted the problem and the upward trend had to be halted. This led to a considerable increase in effort to investigate the noise of turbojet engines.