AN INCREASING attention has been devoted in the recent years to the study of wall turbulence mainly because the succession of events which lead to the fully developed turbulence takes place near the wall. Unfortunately, only few experimental methods can be successfully used in that region. Among them, the electrochemical method appears as the most appropriate, enabling to measure the velocity gradient at the wall, over a distance from the wall not exceeding some micrometers [l-3]. The analysis of turbulent fluctuations can be done in the framework of a linear theory if the ergodicity and the stationarity of the time-dependent fluctuations can be assumed.