Light waves are not considered mechanical waves because they don’t involve the motion of matter.
In longitudinal waves, the vibration or periodic disturbance takes place in the same direction as that of the propagation of the wave. The sound waves are called mechanical waves because they need a material medium( like solid, liquid or gas ) for their propagation. The sound wave involve the vibrations of the particles of the medium through which they travel . Water waves and sound waves are examples of mechanical waves. Compression Waves Sound waves are mechanical waves since they must travel through a medium such as air, water, or solids in order to be heard. Sound waves cannot move through a vacuum.

A sound wave is a mechanical wave that propagates along or through a medium by particle-to-particle interaction. As a mechanical wave, sound requires a medium in order to move from its source to a distant location. Receiving sound waves is the process by which sound travels in form of waves and is received by our eardrums to be heard.

Light waves are different from mechanical waves, however, because they can travel through a vacuum. That is the defining criterion for a mechanical wave, and the answer to your question. Light waves are just one type of electromagnetic … Sound cannot travel through a region of space that is void of matter (i.e., a vacuum). Most of the mathematics and properties of mechanical waves apply to light waves.
Mechanical waves are waves that require a medium in which to travel, i.e., a solid or fluid. Sound waves are mechanical waves because they need a material medium for propagation, like air or liquids like water, or metals like silver. As sound needs a medium to travel, sound is a mechanical wave. Mechanical waves can be classified into two categories based on the motion of the particles – longitudinal and transverse. In transverse waves, the vibration or periodic disturbance takes place in a direction perpendicular to that of the propagation of the wave.