Diesel engine noise is a complex sound source composed of multiple sound sources. According to the way of noise radiation, it can be divided into aerodynamic noise, surface radiation noise and electromagnetic noise. According to the causes, the surface radiated noise of diesel generators can be divided into combustion noise and mechanical noise. Among them, aerodynamic noise is the main noise source of diesel engine noise.

1. Aerodynamic noise is the noise of diesel generator set due to the unstable process of gas, that is, the disturbance of gas and the interaction between gas and objects. Aerodynamic noise directly radiated to the atmosphere, including intake noise, exhaust noise, and cooling fan noise.

2. Electromagnetic noise is the noise of diesel engine set caused by high-speed rotation of generator rotor in electromagnetic field.

3. It is difficult to strictly distinguish between combustion noise and mechanical noise. Generally speaking, diesel engine noise emitted by pressure fluctuations due to combustion in the cylinder of a diesel generator set through the cylinder head, piston, Lianxuan, crankshaft, and body is called combustion noise. Diesel engine noise generated by the impact of the piston on the cylinder liner and the mechanical shock of the moving parts is called mechanical noise. Generally, the combustion noise of direct injection diesel engines is higher than the mechanical noise, while the mechanical noise of non-direct injection diesel engines is higher than the combustion noise. However, the combustion noise is higher than the mechanical noise during low speed operation.