FIG. 16B is similar to FIG. 8 in that the differential amplifier is adapted to process a linear array of signals produced from microphones 900 to the nth microphone to an amplifier 910, with the output inputted to an summing circuit 914, where the output signal is transmitted to a final summing amplifier used in such circuits as described in FIGS. 7A to 13B. The output signal corresponds to substa