U aught to give software AGC a try

Did indeed capture some Maxbotix output using ADC's at 1800Hz & the pings showed up nicely. U could use that for an AGC which defeated reflections, but we're done with sonar. Unfortunately the screenshots R lost, just like the memories of 7.25% sales tax, $1 gas, & $7.50 movies.

Also, before we give up sonar, the optimum frequency for the Maxbotix's was somewhere around 55khz, not the 40khz advertised. The transducers probably need manual tweeking, another reason 3D sonar would have problems.

Finally, tried capturing 10Hz sound with our best condensor microphone. Remember back when U actually bothered with decent microphones & watched home movies on giant screens instead of tiny Goo Tube windows?

Forget about 10Hz sonar. It would take kilowatts of power & ginormous transducers. With a few hundred watts & 30lbs of wood, U can get the condensor to pick up 30Hz.

There are delusions of audible sonar. It would drive people away from the blades. It would be omnidirectional & low powered. The main problem is interference, so what if instead of a sine wave, U spanned several frequencies. The output would be a fixed pink noise pattern U can sense the phase of & a real expensive filter to capture it.