Estimates of transfer functions from measurements contain undesired information -- noise -- whose effect can partly be taken away by applying different smoothing techniques. One such smoothing technique suggests to remove the noise by gating the impulse response in the time domain, hence the name time-gating. This paper shows that time-gating is a special case of a more general smoothing technique. The paper further contains a discussion concerning a preferable choice of time-gating window. An example applied to longitudinal beam transfer functions reflects the necessary trade-off between bias and variance.