It's a little difficult to explain this question .. but I'll try anyway.
To the best of my knowledge propagation models - audio, RF - are modelled as travelling in a sinusoidal form. Surely if a model was constructed based on observation, and then verified by experiment the experiment would more often yield the desired result than not.
Is the model for sinusoidal motion/waves deemed true because the equations are proved true by experiment? How do we know these waves are actually sinusoidal? How was this model developed?