Sound waves are longitudinal.

Explanation:

What are sound waves?
Sound waves are a type of mechanical wave that can be heard by the human ear. They are created by vibrations that travel through a medium, such as air, water, or solids.

Types of waves:
There are two main types of waves: longitudinal waves and transverse waves.

Longitudinal waves:
- In a longitudinal wave, the particles of the medium vibrate parallel to the direction of wave propagation.
- The particles move back and forth in the same direction that the wave is traveling.
- The wave is characterized by compressions (where the particles are closer together) and rarefactions (where the particles are spread apart).
- Examples of longitudinal waves include sound waves and seismic waves.

Transverse waves:
- In a transverse wave, the particles of the medium vibrate perpendicular to the direction of wave propagation.
- The particles move up and down or side to side, while the wave moves forward.
- The wave is characterized by crests (high points) and troughs (low points).
- Examples of transverse waves include light waves and water waves.

Sound waves:
Sound waves are longitudinal waves because:
- The particles of the medium (such as air molecules) vibrate parallel to the direction of wave propagation.
- As the sound wave travels through the medium, it causes the particles to compress and rarefy.
- When a sound wave is produced, it creates areas of high pressure (compressions) and areas of low pressure (rarefactions) in the medium.
- These compressions and rarefactions are what our ears detect as sound.

Conclusion:
In summary, sound waves are classified as longitudinal waves because they involve the parallel vibrations of the particles in the medium. This is in contrast to transverse waves, where the particles vibrate perpendicular to the direction of wave propagation.