Values of SLL obtained with the two algorithms (SA and KOGAN) using the two element beam patterns f_iso (left) and f_dip (right). Each circular point is the mean and σ over N_init = 10 runs. Values for the initial random distributions are plotted with the open circles. Values for the optimised distributions are shown by black filled circles for the KOGAN algorithm and light grey filled circles for the SA algorithm. The dotted line is the best fit of SLL values of the initial random distributions. The stars represent the best solutions obtained over the results of the two algorithms. The arrows indicate out-of-scale values (i.e. cancellation of side lobes). The hollow square represents the maximum SLL of −11.3 dB (with f_iso) and of −14.4 dB (with f_dip) in the case of a 4 × 4 tile with an element spacing of λ/2.