  Context. The height structure of 3-min oscillations over sunspots is studied
in the context of the recently discovered effect of height inversion: over the
umbra, the spatial location of the maximum of chromospheric 3-min oscillation
power corresponds to the relative decrease in the power of photospheric
oscillations. Aims. We investigate whether the height inversion of the power of
3-min oscillations is a common feature of the spatial structure of the
oscillations for the majority of sunspots. Methods. Spectrogram sequences of
H-alpha 6563{\AA} and FeI 6569{\AA} over sunspots, acquired with very high
cadency (about 2 s or better) are obtained. The distribution of the oscillation
power of the line-of-sight velocity signal is studied by using methods of
wavelet frequency filtration and Fourier analysis. Results. The effect of the
height inversion is found in 9 of 11 analyzed active regions. The
interpretation of this effect is possibly connected to both the decrease in the
level of photosphere in sunspot umbrae and the magnetic field topology.
