Sound waves are primarily longitudinal waves , where the particles of the medium vibrate parallel to the direction of the wave's travel. They are also classified as mechanical waves because they require a medium (such as air, water, or solids) to propagate through the mechanical vibration of particles. Additionally, sound waves are considered pressure waves because they consist of compressions (high-pressure regions) and rarefactions (low-pressure regions) as they travel. In summary:

• Sound waves are longitudinal waves.
• They are mechanical waves , needing a medium to travel.
• They are also pressure waves due to the compression and rarefaction pattern.

Sound waves are not transverse waves in air or fluids, though in solids sound can also exhibit transverse wave properties under special conditions.