To ensure the safe operation of roads, periodic monitoring of the condition of the road surface is necessary. Recently, such studies are widely used methods of shallow geophysics. The article presents the results of full-scale experiments, demonstrating the possibility of detecting cavities under a hard road surface by bending standing waves. To isolate standing waves from the acoustic noise recorded on the surface of the coating, we used the accumulation of amplitude spectra of a large number of noise records. The fact that under the influence of acoustic noise bending standing waves are formed in the coating, which are absent in other places, indicates the absence of hard contact at its lower boundary. Thus, by the size of the area on which bending standing waves are formed, it is possible to estimate the horizontal dimensions of the cavity. In addition, the article shows that the analysis of standing waves of vertical compression-tension arising in the coating under the influence of noise makes it possible to control the thickness of the coating.