Diesel engine noise is a complex sound source composed of many kinds of sound sources. According to the noise radiation mode, it can be divided into aerodynamic noise, surface radiation noise and electromagnetic noise. According to the cause, surface radiation noise of diesel generator can be divided into combustion noise and mechanical noise. Aerodynamic noise is the main source of diesel engine noise.

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

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

3. It is difficult to strictly distinguish between combustion noise and mechanical noise. Usually, the diesel engine noise caused by the pressure fluctuation caused by combustion in the cylinder of the diesel generator set radiates outward through the cylinder head, piston, connecting shaft, crankshaft and body is called combustion noise. The noise of diesel engine set caused by the impact of piston on cylinder liner and the mechanical impact of 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, combustion noise is higher than mechanical noise at low speed.