 a hissing noise) somewhere between the points.The sound data is processed through a mathematical algorithm which compares or correlates the two recordings to determine the difference in the times it takes noise to travel from the site of the leak to each of the sensors.If the distance between the sensors is known in advance, this timing information can be used to determine the location of the leak.,

The cross correlation signal of one continuous function, f, with another, g, is defined as