(a) MDI intensity, (b) line‐of‐sight magnetogram, and (c–h) sample maps of the mean travel‐time perturbation covering a portion of the region studied and showing sunspot group AR 9885. Panels c and d show travel‐time maps for filter C at 3 and 4 mHz, respectively (see Table 1). Panels e–h show the travel‐time maps for filter E at 2, 3, 4, and 5 mHz, respectively.