We can justify sound wave as a longitudinal wave with the help of following notions:
1 The vibration of the particles of the medium is parallel to the movement of wave.
2.While performing polarization of sound waves it gives no output.The result of analyzer is negative.This confirms sound as a longitudibal wave.
3.When sound propagates through air , it creates variation of pressure.Pressure rises at compression and falls at rarefaction.
Kamal Dhungel Answered question 2 January 2022