Timeline area
From OpenPSTD
The Timeline area in Blender is a part of the interface that can be used to navigate chronologically. When a listener object is selected it will show the recorded impulse response for the selected object. It will display the range of simulated frames. The currently selected frame is reflected in a green vertical bar, which can be moved to the left and right with the mouse. Doing so will result in the visualisation of the pressure distribution in the 3D View area.