A method and apparatus for providing an average signal characteristic profile derived from signals obtained from different cycles of a cyclically recurring physiological phenomenon. A signal produced from first and second cycles of the physiological phenomenon is sampled at a series of data points to obtain second physiological property values at the data points. The change in the second physiological property values for the first cycle signal between a pair of successive data points and the change in the second physiological property values for the second cycle signal between the same pair of successive data points are determined and averaged. The average change amount is applied to a value of the average signal characteristic profile at one of the pair of successive data points to produce a new second physiological property value for the average signal characteristic profile at the other of the data points of the pair.