Here's why:

* Vibrations and Waves: A vibrating object disturbs the surrounding medium (like air, water, or solids). This disturbance travels outwards as a wave.

* Compression and Rarefaction: Sound waves are longitudinal waves, meaning the particles in the medium vibrate parallel to the direction of wave travel. When the vibrating object pushes outward, it compresses the molecules in front of it, creating an area of high pressure (compression). As the object moves back, it creates an area of low pressure (rarefaction) behind it.

* Propagation: This cycle of compression and rarefaction continues, creating a wave that propagates through the medium.

In simpler terms: Imagine a spring. When you push on it, the coils get closer together (compression). When you pull back, the coils spread out (rarefaction). This is similar to how a vibrating object creates sound waves.