It has recently been discovered how to vary the electron temperature in a simple discharge‐tube plasma over large ranges in a controlled manner. Subsequent use of this technique to study the propagation characteristics of ion acoustic waves in the plasma, as a function of electron temperature, has made it possible to measure properties of both the waves and the plasma: (1) the theoretically predicted dependence of wave velocity on electron temperature has been verified; (2) good agreement was found between a strong damping of the waves occurring at low electron temperatures and a theoretically predicted Landau damping; and (3) an accurate means for measuring the plasma ion temperature has been found.