Two methods for estimating the pressure wavefield generated by a marine air-gun array are tested. Data have been acquired at a ministreamer located below the source array. Effective source signatures for each air gun are estimated. In the first method a nonlinear inversion algorithm is used, where the forward modeling scheme is based upon a physical modeling of the air bubble generated by each air gun. In the second method a linear inversion method is used, with the assumption that the physics in the problem can be described by the acoustic wave equation with explosive point sources as the driving term. From the estimated effective source signatures, far-field signatures have been calculated for both methods and compared with measured far-field signatures. The error energy between the measured and estimated far-field signatures was approximately 8 percent for both methods.