Longitudinal waves include sound waves and certain seismic waves. We explored the parameters that determine the pitch of a vibrated string or a plucked piece of metal. We spun a tube of corrugated plastic; the faster you spun the tube, the higher the pitch of the sound produced.
If the seismic waves from an earthquake are detected at three different locations, you can figure out where the epicenter of that earthquake was. We located the epicenter of several "earthquakes" in the "Land of Oz".