Question about Propagation of a Mechanical Wave

Someone asked :

What are the basic properties that a medium must possess to have the propagation of a mechanical wave? 

 

And Founder of APG ( FAPG ) was answering ?

The necessary condition is the elasticity of the medium. This means that for a wave to be produced in a medium, the medium must be elastic and continuous. After the wave is generated, we must examine the propagation conditions. What are the conditions for wave propagation?! Here, the Physics of scales helps us. we measure the parameters of the wave (note that the speed of the wave is determined by the coefficient of elasticity and density of the medium) and we compare them. If the amplitude is greater than the wavelength, the wave propagates easily, but if it is smaller, the wave stops (Absorbed by the medium). (M.Sh)