The 3-minute oscillations that dominate the solar chromosphere have been attributed to the natural response of the plasma to external disturbances by oscillating at a characteristic frequency equal to the acoustic cutoff at the temperature minimum. This is predicted to be true for continuous or impulsive bursts of energy. Here we study the spatial distribution of 3-minute power for three flares of GOES class C8.3, M7.3, and X2.2 during pre-flare, flare, and post-flare phases. Using intensity images in thermal ultraviolet (UV) emission centered on 1600 and 1700 Angstroms, we compute power maps by applying pixel-by-pixel Fourier transforms in the temporal direction covered by each time window. Non-thermal hard x-ray (HXR) data from RHESSI is used to examine the location of 3-minute oscillations relative to flare loop footpoints anchored in the lower atmosphere.