Some recent column source designs incorporate ‘beam steering', where the phase of each element in the column is varied in order to change the angle at which the major lobe appears. This technique may be used to improve speech intelligibility by boosting the ‘direct-reverberant ratio' of energies received by a segment of an audience within a built environment - a technique which will be explored further in the Module ‘Room Acoustics'.
Investigate beam steering by incorporating a phase difference between the velocities of your pistons in the column model. (In the first instance it is probably best to use a fixed incremental time delay between each successive source - you should experiment). Note the behaviour of the major lobe as the phase difference is varied, and also any changes taking place in the sidelobes. Hint - Kinsler and Frey have something to say regarding beam steering.