Engine Noise Due to Mechanical Impacts at Pistons and Bearings

In this paper the noise of engines of different size, duty and combustion system are compared. Measured differences, not consistent with combustion charges, are analysed in detail and these differences are shown to be the result of mechanical impacts.

Results suggest that the kinetic energy of impact is not the only significant parameter influencing mechanical noise, and in the general case the magnitude of the force accelerating a component across a clearance must also be considered.

The analysis shows that the dominant parameters affecting the magnitude of the impact change with speed and size of engine and offers an explanation for the apparent discrepancies observed in some previously recorded data.