It cannot travel through vacuum because sound travels by producing a vibration in the molecules of the medium surrounding it. And there are virtually no molecules in vacuum.
When a body produces sound it produces vibrations. These vibrations cause the medium molecules (air, water or solid) to vibrate.
As the sound wave propagates, the molecules themselves do not move from one point to another, they only vibrate at the mean position. It is the effect that propagates and reaches our ears.
The ear can be broadly classified into three parts: the outer ear, the middle ear, and the inner ear.
Outer ear:
The part of the outer eat that is visible to us is called pinna. The pinna collects sounds waves and directs them to the ear tube. At the end of the ear tube is the ear drum.
When the ear drum vibrates sound waves are transmitted to the middle ear.
Middle ear:
The middle ear is a cavity with three important ear bones. Vibration of these bones transmits the vibration to the inner ear.
