The Ejs Simultaneity model displays the effect of relative motion on the relative ordering of the detection of events.  The wave source and two equidistant detectors are at rest in reference frame S', which moves with constant velocity, v, in frame S.  The initial relative velocity as well as whether the wave source emits sound waves or light can be changed.  You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu item.  

Ejs Simultaneity model was created using the Easy Java Simulations (Ejs) modeling tool.  It is distributed as a ready-to-run (compiled) Java archive.  Double clicking the ejs_ehu_sr_simultaneity.jar file will run the program if Java is installed.  Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models.  Additional Ejs models for special relativity are available.  They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Please note that this resource requires at least version 1.5 of Java (JRE).