Let the laboratory reference frame be based on a standing wave: its oscillations serve as a standard of simultaneity; period and wavelength are standards of time interval and length. Standing wave can be represented as a superposition of two counter harmonic waves having the same frequency and amplitude. Nodes are stationary in the standing wave, and the oscillations are in-phase. Nodes will begin to move with a difference in frequencies. The distance between nodes is reduced, and oscillations become slower. These effects are described by formulae of Lorentz effects. If we associate the new reference frame with this moving wave, the Lorentzian effects will prove to be relative. The cause of relativity lies in the fact that, besides the wave compression and slowing down of oscillations, the phase synchronism of oscillations is disrupted in terms of the laboratory reference frame. In the new frame, these oscillations are considered in-phase, and then phase synchronism of laboratory clocks is disrupted. Relativity of simultaneity arises with all the consequences known from the theory of relativity. This model is well suited to illustrate the essential relativistic laws and can be used in teaching. Furthermore, the wave approach is based on conception of space materiality and plays an ideological role. The first section is devoted to the calculation of the proper time of an observer moving with variable velocity.