bat radar, making an echo-vision device for the blind

1)  They have a muscle in the ear connected to the stirrup bone to turn off the ear's hearing when sending out the loud pulses.  Up to 50 times a second.
2) They can increase pulse rate when needed
3) The pulses reduce in frequency over the duration of the pulse to identify how far away echos come from. 
4) The beginning of the pulse might be constant to determine how fast the target is moviing via doppler effect.
5) ears move rapidly for an unknown reason
6) can distinguish from other bat echos possibly simply by the brain filtering out any received "pictures" of the world that do not make sense

I've thought about making an ultrasound device for the blind.  Place emitter in the high the center of the chest.  Cut received frequencies down to hearing range.  Use 4 receiving microphones, 2 on each side of hips or shoulders and about 6 inches apart vertically.  Then 4 earphones, 2 in front of each ear, about 1 inch apart.  So vertical and horizontal triangulation is magnified thanks to greater separation of the microphones than the earphones.  Also use 1) and 3) above. I would make 3) follow notes on a keyboard.  A loud low frequency note would be something big, further away.  Maybe use 2 octaves, 24 notes.

Or make the emitter, recievers, and headphones all part of a hat.