Abstract: Modal array signal processing technique, which is based on the principles of wave propagation and wave scattering, are presented in this paper. The derivations of modal array signal processing algorithms for both frequency- domain and time-domain broadband beamformer are discussed. Results of simulations show good performance of the modal array processing algorithms. Using the similar process technique, other modal array signal processing algo- rithms can also be derived. The modal beamforming approach is computationally more efficient compared to a classical element-space array processing because the number of signal processing channels is reduced and the look direction of the beamformer can be tactfully decoupled from its beampattern shape. However, the modal array processing technique can only be applicable to symmetrical arrays such as spherical arrays and cylindrical arrays.