Tunnel micro-pressure waves are one of the most important environmental issues associated with the aerodynamics of current high-speed trains in Japan. When a train enters a tunnel, compression waves are formed. This pressure waves then travel through the tunnel at the speed of sound, and finally, they radiate as pulsed pressure waves when they reach the tunnel exit; the larger the peak value, the louder the sound impact becomes near the tunnel mouth. In this study, an experimental work was conducted with a new reduced-size model of a train car and a tunnel model, and in this experiment, running experiments were performed to reproduce the formation of micro-pressure waves in the tunnel. The pressure inside the tunnel was measured, and finally, the data was analysed using a data acquisition software. Moreover, a three-dimensional numerical experiment replicating the experimental conditions was carried out to simulate the flow around a high-speed train running through a tunnel. The rhoPimpleFoam solver, which uses the flexible PIMPLE algorithm for time-resolved, pseudo-transient simulations, in OpenFOAM was used for simulating the flow field.