Echolocation is the method of interpreting sound that reflects off of surrounding objects in order to distinguish where and what the objects are. Why shouldn't everyone know how to do this?
It's what dolphins, bats and whales use, but they use much higher frequencies than humans can hear. Human-audible frequencies act the same and with practice blind and seeing people have been able to use this skill to acquire a new set of data regarding their surroundings; in effect, another "sense".
This is my exploration of the learning process of echolocation. I'd encourage everyone to at least acknowledge this amazing sense that we have overlooked for many thousands of years, and give it a whirl.