Sound wave are longitudinal wave because particles of the medium through which the sound is transported vibrate parallel to the direction that the sound wave moves.

Understanding Sound Waves
Sound waves are categorized into different types based on how the particles in the medium vibrate in relation to the direction of wave propagation. One of the primary types is the longitudinal wave.
Definition of Longitudinal Waves
- Longitudinal waves are characterized by particle displacement parallel to the direction of wave travel.
- In these waves, the medium's particles compress and rarefy, creating areas of high and low pressure.
How Sound Waves Fit This Definition
- Vibration Direction: In sound waves, particles in the medium (like air, water, or solids) vibrate back and forth along the same direction as the wave travels.
- Compression and Rarefaction: Sound waves consist of alternating compressions (where particles are close together) and rarefactions (where particles are spread apart).
Examples of Longitudinal Waves
- Sound in Air: When a person speaks, vocal cords create compressions and rarefactions in the air, transmitting sound to the listener's ears.
- Ultrasound: Medical imaging techniques utilize high-frequency sound waves, which are also longitudinal, to visualize internal structures in the body.
Conclusion
Understanding that sound waves are longitudinal helps in grasping their behavior and propagation through various media. The parallel movement of particles not only defines their nature but also explains various acoustic phenomena we experience daily.