The sound emitted by a diesel engine is a smooth, rhythmic and coordinated sound in the normal working condition. If the engine is in operation, accompanied by other sound, such as intermittent or continuous metal knocking, continuous metal friction, that is, the engine operation is not normal, this sound is called the diesel engine noise. Abnormal noise of diesel engine is an important form of engine failure, and is an important basis for judging and analyzing faults. Once the abnormal sound appears, it shows that the technical condition of a certain diesel engine has changed. The abnormal noise of diesel engine has certain regularity. If we can grasp the fault characteristics of diesel engine abnormal sound, it will be very helpful for diagnosing and eliminating diesel engine faults. Most of the abnormal noise of diesel engine depends on the speed of diesel engine. When the diesel engine speed changes, the motion speed of each moving machine will also change. Especially in rapid acceleration or rapid deceleration, the motion parts will produce a certain acceleration or speed reduction. On the one hand, the inertia effect may lead to the new abnormal noise, on the other hand, it will make the original not obvious difference become clear. Therefore, most of the abnormal noise faults of diesel engines depend largely on the rotational speed of diesel engines.