Deterioration of average evoked potential waveform due to asynchronous averaging and its compensation

In order to improve the signal-to-noise ratio of evoked potentials, the responses to repetitive stimuli are usually recorded, and the averaging method is applied to them. If each starting point of the averaging varies with respect to the response because of asynchronous sampling of the measurement data, the average waveform of the evoked potential signal is distorted by the averaging. We analyzed the asynchronous averaging in the frequency domain and derived a relationship between the fluctuating time and the degree of the deterioration. By using this relationship, a required sampling rate was derived to ensure the accuracy of the averaging. Furthermore, we also deduced a compensation procedure for the asynchronous averaging in case of coarse sampling.