1. A method of accumulating data for use in determining the signature of an array of n interacting seismic sources, comprising the steps of: actuating the array of n interacting seismic sources; measuring the emitted pressure wave in the near field of the array by means of n transducers of known sensitivity located at n respective independent points whose positions are known with respect to the n interacting seismic sources so as to obtain data from each of the n transducers; storing the data from each of the n transducers for subsequent processing to obtain the signature of the array; providing an array of n marine seismic sources as the array of n seismic sources; providing n hydrophones for measuring the emitted pressure wave; subsequently processing the data by: forming n simultaneous equations ##EQU6## where h.sub.i (t) is the signal provided by the ith hydrophone, S.sub.i is the sensitivity of the ith hydrophone, a.sub.ij is the distance between the ith hydrophone and the jth seismic source, c is the speed of sound in water, t is time, and P'.sub.j (t) is the equivalent signature of the jth seismic source; and solving the n simultaneous equations for P'.sub.j (t) where j=1, 2,. .. , n.