The Toolbox provides you with a function for plotting your simulated sound fields (plot_sound_field()) and adding loudspeaker symbols to the figure (draw_loudspeakers()). If you have gnuplot installed, you can use the functions gp_save_matrix() and gp_save_loudspeakers() to save your data in a way that it can be used with gnuplot. An example use case can be found at this plot of a plane wave which includes the Matlab/Octave code to generate the data and the gnuplot script for plotting it.