Noise from Aircraft Turbomachinery

Abstract

ynoise problem, necessitating federal noise limits on individual aircraft. Much of the effort is devoted to reduction of the noise due to turbo­ machinery, �ince it produces the most troublesome noise in modern high-bypass turbofans. A correspondingly large portion of this review is devoted to this sub­ ject, and indeed, because of the interests and knowledge of the authors, to a par­ ticular aspect of the problem, namely. prediction of the noise level from the blading geometry. A second aspect of the overall noise problem is the connection between noise production and performance, measured in terms of thrust per unit of airflow and thrust per unit of engine weight. The possibilities for noise reduction offered by reduction of the thrust per unit of airflow, as opposed to more direct noise­ abatement techniques such as duct treatment, and particularly jet suppressors, may not be fully appreciated. A very brief outline of the recent work on supersonic jet noise, motivated by the problems of supersonic commercial aircraft, is given, but justice is not done to this very complex subject.