Coherent averaging technique: a tutorial review. Part 1: Noise reduction and the equivalent filter.

Coherent averaging is used to recover the response to repetitively applied stimuli when that response is embedded in random noise, and when the signal/noise ratio is fractional. In this paper the improvement in s/n ratio due to averaging is calculated; it is also shown that averaging acts as a filter which attenuates periodic interference when it is not time-locked to the stimulus; the characteristics of this filter are derived.