The crackling noise due to scratching superhard nanocomposite coatings was investigated by using a simple stick-slip model. The optimum information extracted from statistical analysis, in terms of the Akaike information criterion, is in good agreement with real tests. As a nanocomposite coating approaches an optimal performance, the acoustic emission energy follows a power-law distribution and its behavior is likely to be independent of microscopic and macroscopic details. The results imply that a peculiar deformation behavior, due to the competition between different deformation mechanisms such as dislocation pile-ups in nanocrystalline grains and grain sliding-grain rotation within amorphous boundaries, plays a vital role in the nanostructure with superhardness.