Answer:
Vacuum
Step-by-step explanation:
Sound waves are usually defined as longitudinal waves that are characterized by the motion of the particles parallel to the direction of wave propagation. This sound wave can travel only through the medium such as air and water. But they cannot travel through a vacuum. It is because there is no particular medium in space through which sound could propagate and the pressure in the vacuum is extremely low, much lower than the normal atmospheric pressure, due to which any type of particles present in space are not being affected by any type of processes.