In longitudinal waves, particles of the medium move in a direction parallel to the direction of propagation of the disturbance.

The regions where the coils become closer are called compressions (C).

The movement of vibrating objects creates pressure variations in the medium, leading to the propagation of sound waves.

Sound propagation can be visualized as the propagation of density or pressure variations in the medium.

Pressure is related to the density of particles in a medium. More density results in higher pressure, and vice versa.