A teacher strikes a tuning fork and holds it close to the open end of a hollow tube. A student at the far end of the tube hears a clear musical note. Explain how sound travels from the tuning fork to the student's ear, referring to compressions and rarefactions.

The vibrating tuning fork sets the surrounding air particles into oscillatory motion.

These oscillations produce alternating regions of compression, where the particles are pushed closer together, and rarefaction, where they are spread further apart.

The compressions and rarefactions travel along the tube as a longitudinal wave, with the particle displacements parallel to the direction of wave propagation.

Thus energy is carried from the tuning fork to the student’s ear by the wave, while the air particles themselves only oscillate about their equilibrium positions and do not undergo a net transfer of matter.