Computer Optimised Design of Engine Structures for Low Noise

The paper describes a computer optimisation procedure, using static deflection techniques, by which the overall noise level of an engine can be reduced by up to 5dBA by minor modification. The computer program operates within given weight, space and strength constraints and produces a modified design which can be machined by existing plant.

The use of the static deflection technique is justified by the results of running engine damping measurements and by the analysis of the influence of damping on typical third octave vibration levels. This analysis demonstrates that the damping of the block structure has very little influence on running engine vibration levels, which are, in fact, controlled by the stiffness.