Measuring velocity of sound with nuclear resonant inelastic x-ray   scattering
  Nuclear resonant inelastic x-ray scattering is used to measure the projected partial phonon density of states of materials. A relationship is derived between the low-energy part of this frequency distribution function and the sound velocity of materials. Our derivation is valid for harmonic solids with Debye-like low-frequency dynamics. This method of sound velocity determination is applied to elemental, composite, and impurity samples which are representative of a wide variety of both crystalline and noncrystalline materials. Advantages and limitations of this method are elucidated. 
Michael Y. Hu, Wolfgang Sturhahn, Thomas S. Toellner, Philip D.   Mannheim, Dennis E. Brown, Jiyong Zhao, E. Ercan Alp