Designing Analog and Digital Optimum Filters

Signal and noise can be separated by conventional frequency filters only if the two have different frequency contents. This is not normally the case for geophysical applications. In explosion seismology, for example, the spectrum of the noise covers the same frequency range as the seismic signals, while the signal-to-noise ratio differs for different frequencies. The purpose of a conventional frequency filter is to extract those frequency components for which the signal-to-noise ratio is large relative to other frequency ranges. The pass and reject bands are determined from the results of a spectral analysis and other information about the signal and noise spectra.