Question

What is the most important property of a wave motion (of sound wave) and why?

Answer 1

The most important property for the sound wave is to have a medium for propagation, the medium should possess elasticity, as the sound wave is a mechanical wave

Answer 2

Sound is one of the most important physical substances,more accurately it is one of the most important physical frequencies present in our planet earth.

The most basic and most important feature of any sound wave is that,these waves need a physical medium of propagation to vibrate and produce the sound.

That's why we cannot hear anything in the outer space ,as there is no air which is the most common medium of the sound wave propagation.