The desire beampattern of a sound source at the far field can be synthesised by controlling the relative amplitudes and phases of each array element. However, when one or more elements in the array fail, the beampattern at the far field is severely distorted. The Goal Attain optimisation algorithm is used to adjust the relative gains of theremaining array elements so as to generate an optimised pattern closely resembles the original beam pattern. The quality of each optimised pattern is evaluated and compared based on a defined performance index. The effectiveness of the Goal method is tested in both the Uniform Planar and Linear Array sonar systems.