STUDIES ON THE COMBUSTION NOISE IN DIESEL ENGINES - 1. SEPARATION OF COMBUSTION NOISE FROM ENGINE NOISE.

An attempt was made to separate the combustion noise and the mechanical noise from the engine noise by estimating the transfer coefficient between the cylinder pressure spectrum and sound pressure spectrum of noise in a four-stroke diesel engine. The relation between the cylinder pressure and the sound pressure on each frequency was assumed as follows. (Engine Noise) equals (Mechanical Noise) plus (Transfer Coefficient) multiplied by (Cylinder Pressure) As a result of the investigation on the experimental results, it was clarified that the transfer coefficient was not influenced by the engine speed, and the frequency characteristics of the transfer of vibration and noise were obtained.