Internal combustion engine silencer and internal combustion engine

The utility model discloses an internal combustion engine silencer and an internal combustion engine. The internal combustion engine exhaust silencer comprises a cylinder body, a gas inlet pipe, and a gas outlet pipe. An expansion cavity is formed in the cylinder body. The gas inlet pipe and the gas outlet pipe are communicated with the expansion cavity. A resonant cavity is formed in the cylinder body. A resonant cavity separating plate for separating the expansion cavity and the resonant cavity is further arranged in the cylinder body. A connecting pipe for communicating the expansion cavity and the resonant cavity is arranged on the resonant cavity separating plate. The gas inlet pipe and the gas outlet pipe are communicated with the expansion cavity. When gas penetrates through the internal combustion engine silencer, the gas penetrates through the gas inlet pipe into the expansion cavity, intermediate-frequency noise can be eliminated. In addition, part of the gas into the expansion cavity can enter the resonant cavity through the connecting pipe on the resonant cavity separating plate, a standing wave is formed in the resonant cavity, and thus low-frequency noise is eliminated. Therefore, noise of the gas exhausted by the expansion cavity and the resonant cavity can be effectively reduced.