The document discusses seismic data processing techniques in the frequency-wavenumber (f-k) domain. It defines the f-k domain as a two-dimensional Fourier transform over time and space. Noise like groundroll and multiples can be more readily separated and filtered in the f-k domain before inverse transforming. Spatial aliasing is also discussed, and the Nyquist criterion and proper trace sampling are important to avoid aliasing. Filtering techniques like pie-slice filters in the f-k domain can be used to remove noise like groundroll.