Engine Radiated Noise

Some empirical noise prediction models have been derived from a sample of 1m radiated engine noise measurements.

Normally aspirated direct injection diesel

Turbocharged direct injection diesel

Indirect injection diesel

Petrol engines (lean burn)

Petrol engine formula updated for 1990′s

The updated formula for petrol engine radiated noise shows that the noise increases by 40dB/decade for the stroke compared to 30dB/decade for the bore. Crankshaft stiffness has an effect on radiated noise and is included as a first approximation with the bore and stroke as these have a direct effect on the design of the crankshaft.

See also: Engine Excitation Mechanisms, Engine Orders, Radiated Noise.