(1) Causes of mechanical noise and combustion noise

1) Mechanical noise

Mechanical noise is mainly generated by vibration and mutual impacts caused by periodic changes in gas pressure forces and inertial forces of moving parts during engine operation. It mainly includes noise from the piston-crank-connecting rod mechanism (mainly high-frequency noise); noise from the valve train (mainly low- and mid-frequency noise); transmission gear noise (its noise spectrum is continuous and wide); and mechanical vibration and noise caused by unbalanced inertial forces.

2) Combustion noise

Combustion noise refers to structural vibration and noise generated during the combustion process. The sound pressure level of combustion noise inside the cylinder (especially the low-frequency part) is very high, but most components in the engine structure have relatively high rigidity, and their natural frequencies are mostly in the mid- to high-frequency range. Due to the mismatch in response to sound propagation frequency, the very high in-cylinder pressure peaks in the low-frequency range cannot be transmitted smoothly, while the mid- and high-frequency cylinder pressure levels are relatively easier to transmit.

(2) Control methods for mechanical noise and combustion noise

1) Vibration isolation treatment

High-efficiency vibration-damping rubber pads are generally used for generator set vibration isolation. After vibration isolation treatment, the vibration on the surface of the generator set is effectively blocked.

2) Noise reduction treatment

Noise reduction treatment is carried out along the noise transmission path to reduce external radiation from the source. For generator rooms with stringent noise control requirements, high-efficiency sound-absorbing materials should also be applied to the interior, so that noise can be effectively attenuated and the room's overall noise reduction performance can be improved.

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