Mechanical wave momentum from the first principles
  For steady-state and some other types of mechanical waves of an arbitrary form, intensity and nature, propagating in a free uniform waveguide, we present the following. Relations for the axial momentum as it directly follows from the conservation laws. The mass associated with the wave. The connection between the wave energy and momentum. The structure of a binary wave which possesses a self-equilibrated momentum, in particular, a transverse-longitudinal wave formed upon excitation of flexural waves. Conditions under which longitudinal sinusoidal waves can carry momentum and the physical meaning of the so-called "wave momentum". 
Leonid I. Slepyan
physics.gen-ph