An averaging method which eliminates periodic strays and which is usable in analog-digital computers performing an averaging procedure. Such a procedure which processes a set of signals picked up from an examined object elicits an averaged evoked response due to its capability of reducing internal noise and periodic strays originated in an environment comprising a mains supply network proportionally to the square root of N sweeps of the procedure, and in the case where the periodic strays and external stimuli are synchronous, the averaged periodic strays are not sufficiently reduced and distort the averaged evoked response making its right interpretation difficult. In order to overcome the latter problem, the averaging method eliminates the periodic strays from the set of signals during the averaging procedure in greater extend i.e. proportionally to the number of N sweeps of the averaging procedure resulting in their at least N-fold reduction thanks to introducing permanent desynchronization between the frequency ? of the external stimuli and the frequency ? of the periodic strays and thanks to introducing an odd number K of half-periods of the frequency ?, which number K determines the value of the period T according to the formula: T = ? t K, where K is a natural and odd integer.
AVERAGING METHOD FOR PERIODIC STRAYS ELIMINATION AND THE COUNTING CIRCUIT FOR EVOKED RESPONSES MEASURING SET-UP FOR APPLYING THE METHOD