Why cannot mechanical wave travel in vacuum?​

Because mechanical waves rely on particle interaction in order to transport their energy, they cannot travel through regions of space that are void of particles. That is, mechanical waves cannot travel through a vacuum.

Explanation:

Since mechanical waves depend on molecule cooperation to move their energy, they can't go through areas of room that are drained of particles. That is, mechanical waves can't go through a vacuum.

Explanation:

it would be a gas formation