Sound propagation refers to the movement of sound waves through various mediums. One important factor that affects sound propagation is the density of the medium. In general, sound travels faster through denser media. For example, sound travels faster through solids than through liquids, and faster through liquids than through gases.

When sound waves encounter a medium, they cause the particles in the medium to vibrate, which in turn transfers the sound energy. In solids, the particles are closely packed, allowing for efficient transfer of energy, resulting in faster sound propagation. In gases, however, the particles are further apart, leading to slower sound propagation.

Our brains are responsible for perceiving and interpreting sound. Sound waves enter our ears and cause the eardrum to vibrate. These vibrations are then transmitted through tiny bones in the middle ear, eventually reaching the cochlea in the inner ear. The cochlea is filled with fluid and contains thousands of tiny hair cells that convert the mechanical vibrations into electrical signals. These electrical signals travel through the auditory nerve to the brain, where they are interpreted as sound.