Exploiting high-resolution observations made by the Solar Optical Telescope onboard
Hinode, we investigate the spatial distribution of power spectral density of oscillatory
signal in and around NOAA active region 10935. The G-band data show that in the umbra
the oscillatory power is suppressed in all frequency ranges. On the other hand, in
Ca II H intensity maps oscillations in the umbra, so-called umbral flashes, are clearly
seen with the power peaking around 5.5 mHz. The Ca II H power distribution shows the
enhanced elements with the spatial scale of the umbral flashes over most of the umbra
but there is a region with suppressed power at the center of the umbra. The origin
and property of this node-like feature remain unexplained.