Saw Daniel Kish give a lecture a few months ago, and this amazing ability is a lot more accessible than it sounds. Kish uses both passive and active sonar (base

Saw Daniel Kish give a lecture a few months ago, and this amazing ability is a lot more accessible than it sounds. Kish uses both passive and active sonar (based on dental clicks), but the passive sonar is a lot easier to wrap your head around. Even for people with sight, the difference between a large, echo-y room and a small room is immediately apparent. The differences between a voice spoken in front of a hard table and a soft pillow are also very distinct. And if you make an even tone in front of a wall and in front of a corner, the differences are quite apparent as well. Apparently corners are so acoustically distinct that you can hear them from quite a distance away. It's not a foolproof method; he uses a cane because it's difficult to hear objects below knee level. But he thinks many more people can learn to "hear the walls" (if we don't ridicule people for it).