sirch:
cr0sh - I didn't post it because there is nothing to it, 7 ultrasonic transducers in parallel with a 1mH inductor in series. The size of the inductor depends on the capacitance of the particular transducers you ar using.
My apologies; upon re-reading that section, I can see now that you set it up for "fixed" beam-forming. I'd be really curious about the electronic steering part; changing the amplitude of the output pulses electronically would be an interesting expansion - I wonder if changing the timing of the pulses would have any useful effect (or just result in a garbled reception). Lot's of room for experimentation, I suppose.