An air filter is a device that filters the air entering the engine. The resonator is an empty container installed in parallel next to the air filter to stabilize the intake air flow and reduce the noise of the air flow. The design idea of the resonator is to refer to the lake in the river and play the role of stabilizing the river water. But there is still insufficient evidence to see whether the resonator is useful or not, so most cars still do not have the extra part of the resonator installed. Cars with resonators are generally designed to improve the grade of the vehicle without much effort, so these vehicles often have more superfluous designs and actions in addition to the dispensable resonator.