Forced drainage configurations are often employed to control the liquid fraction in a foam column. In that, a constant flow of liquid is added at the top of the column, draining down through the foam, yielding a steady liquid fraction distribution. When the injected flow rate is subjected to pulsations, the liquid fraction pulsates as well. We performed time-resolved neutron radiography measurements to investigate the spatial and temporal distribution of these pulsations throughout the foam column. For high pulsation frequencies or low drainage flow rates, the pulsations are damped within a few millimeters from the injection point. Pulsation of lower frequencies or higher flow rates might spread several centimeters through the column. The results allow to estimate the influence of pulsating feed pumps on the liquid fraction distribution under forced drainage.