One of the causes of the deviation of the signal‐to‐noise array gain from its ideal value is the existence of random amplitude and phase fluctuations of the signal and noise waveforms arriving at the elements of the array. The effect of normally distributed fluctuations on both the signal and noise gains is examined in this paper. An equation is developed which gives the gain, when there are fluctuations, as a function of the ideal gain for both the signal and noise. The expressions for the signal and noise gains used in this paper are valid for all single‐frequency fluctuations arising between the source and the point in the array where the output is measured. It is shown that under certain conditions the total signal gain degradation due to fluctuations can be approximated by the sum of the degradation due to fluctuations in the medium and the degradation due to fluctuations in the equipment.