The only way to know for a given sample of indeterminate composition is to ping it, measure time delay of propagation, and find out. Are they dispersive media for propagation vs. frequency? Does amplitude matter? Look at the densities of liquid and solid paraffin. A highly compressible medium will have its properties depend on temperature and depth.

Are the media inhomogeneous over the distance of a wavelength or more? Are there particulates to cause scattering? Is there composition stratification?

Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz3.pdf