Here's why:

* Needs a medium: Sound waves require a medium (like air, water, or solids) to travel. They cannot travel through a vacuum.

* Vibration and displacement: Sound waves are created by vibrations that cause particles in the medium to move back and forth, creating areas of compression (higher density) and rarefaction (lower density).

* Energy transfer: The wave itself doesn't travel, but the energy from the vibrations does, allowing us to hear the sound.

Other examples of mechanical waves include:

* Water waves: These are caused by disturbances on the surface of water, creating crests and troughs.

* Seismic waves: These are waves that travel through the Earth's crust, caused by earthquakes or volcanic eruptions.

* Waves on a rope: If you shake one end of a rope, you create a wave that travels down the rope.

Key takeaway: Mechanical waves are waves that need a physical medium to travel, and they transmit energy through the vibration and displacement of particles within that medium.