First, check the engine belt. If there are multiple belts in the car and you can't judge which belt is the problem, you can start the car first, and then pour some water on the belt. If the abnormal noise disappears, it means that there is a problem with the belt. You can see if it is loose or of poor quality.
The engine belt makes abnormal noise. Pouring with water is to increase its stickiness. In fact, it improves the stickiness of the belt. But after the water is dry, the belt will return to its original state, which is the principle of belt watering.