How can I find out if a medium is dispersive or not

[Fourier mn]

Homework Statement

How can I find out if a medium is dispersive or not, only with its wave equation?

Homework Equations

The Attempt at a Solution

 

[gabbagabbahey]

Well, what physical quantities are affected by whether or not a medium is dispersive? What is the wave equation in a general medium?

 

[turin]

What is the wave equation in a general medium?

I am eagerly awaiting the answer to this question, and I would be satisfied to find out what is the wave equation in a generally dispersive medium (and frequency domain equation doesn't count).