1. A method for processing seismic signal data comprising: inputting seismic signal data in at least one groups of related trace signals; summing and determining average signals for a selected number of successive traces in each of said at least one groups; determining the correlation matrix for the at least one groups and constructing plural orthonormal basis waveforms; estimating the common signals of said at least one groups of a linear combination of selected ones of said orthonormal basis waveforms; and outputting the common signals as a noise reduced representation of said at least one groups of seismic signal data.