We consider free vibrations of an infinite ideal homogeneous string, that described in the laboratory reference by the equation u_tt =a²u_xx. We propose a model in which the role of frames is performed by the standing waves. The concept of motion in the model is analyzed. It is shown that there exist an infinite number of equivalent frames of reference moving relative to each other. Distances, intervals of time, speeds obey the formulas of special theory of relativity, in which the role of invariant speed is performed by the constant a.

Key words: special relativity, frame, standing waves.