IHC response in comparison to track distances. as function of place. The left vertical axis represents IHC response while the right vertical axis represents time difference between the tracks (in milliseconds). The line in blue, red, and black represents mean track distance, standard deviation of the track distances and the average IHC response over time. It may be observed that the track distance rises in discrete steps, with small steps corresponding to high IHC response, and high steps corresponding to low IHC response and high standard deviation. Three regions labelled as "1", "2", and "3" between dotted vertical lines, have been identified as Perceptually Relevant Regions (PRR). The plot corresponds to the same response in 5 averaged over time and with an extended range in place.