The correct answer is option 4: Polarisation.

1. Reflection: Sound waves can exhibit the phenomenon of reflection, which is when waves bounce off a surface. For example, when sound waves hit a wall, they are reflected back, allowing us to hear echoes.

2. Refraction: Sound waves can also exhibit refraction, which is the bending of waves as they pass through different mediums, such as air and water. This is why sound can appear to change direction when passing through different layers of the atmosphere.

3. Interference: Sound waves can demonstrate interference, which is the phenomenon when two or more waves overlap. This can result in constructive interference, where waves combine to create a louder sound, or destructive interference, where waves cancel each other out.

4. Polarisation: Sound waves, unlike light waves, cannot exhibit the phenomenon of polarisation. Polarisation is the process by which the direction of vibrations in a wave is restricted to a specific plane. This phenomenon is only observed in transverse waves, such as light waves, but not in longitudinal waves like sound waves.

Therefore, the correct answer is option 4: Polarisation.