When the air conditioner is running, some products will occasionally produce "Hua Hua" sound, is it normal?

During the operation of the air conditioner, the internal refrigerant state changes constantly, from liquid state to gas state, and then from gas state to liquid state. This normal physical phenomenon flows at a certain speed in the refrigeration system. Due to certain resistance, it will produce a kind of "Hua Hua" sound of flowing water, which is a normal phenomenon, especially in the dead of night.