Mechanical waves move through matter as a medium and as such many of the natural laws that pertain to motion and dynamics have special places in the study of mechanical waves. One type of wave is sound which most easily propagates through air however because of the laws of momentum one could expect that a mechanical wave is maintained through any matter. A solid barrier for example would be so rigid that it would absorb the impact of a wave and impede passage slightly beyond the barrier. This would produce a sound shadow where the sound loses its momentum in passage through the solid.
Anyways this is the last blog post. Thanks FizziksGuy, even in the darkest of nights, you were by my side all along, my true mentor,