Both phonons diffraction and interference patterns are observed at the atomic scale in nanocomposite systems containing crystalline silicon and obstacles of nanometric voids or amorphous silicon inclusions with dimensions of the same order as the phonon wavelengths. The phonon diffraction and interference patterns due to these nano-architectured systems are similar to the ones predicted by a simple Fresnel- Kirchhoff integral. These findings give evidence of the wave nature of phonons, and they can increase the comprehension of the phonons interaction with nanoobjects and at long term they can be useful for intelligent thermal management strategies and devices as well as a phonon frequency filtering at the nanoscale.