A friend sent me this article on blind persons using echolocation. I found it an amazing account of mental composure/creativity, concentration and the sense faculties: http://www.telegraph.co.uk/news/worldnews/asia/china/11481496/Chinese-barefoot-lawyer-escaped-house-arrest-using-bat-like-echolocation.html?WT.mc_id=e_DM7009&WT.tsrc=email&etype=Edi_Wor_New&utm_source=email&utm_medium=Edi_Wor_New_2015_03_20&utm_campaign=DM7009 

Several people are mentioned in the article, so the article can lead to more examples of human echolocation if one is interested.

Very cool. Made me think of this documentary I watched a few months ago, the boy who sees without eyes: https://www.youtube.com/watch?v=AiBeLoB6CKE

This kind of thing reminds me of a sound that I find easy to hear.
It's a sound that comes from most walls.
It's not echolocation, because I can only tell if I have walls or something at my sides or not, and don't need to make a sound like blind people do.

There is a trick to hearing it.
To identify this sound, go with one ear next to a wall in a quiet place, and then slowly move your ear farther and closer to the wall.
You will hear a subtle sound (but not subtler than sounds from your own body), which is a bit high-pitched (but not as much as a tinnitus sound).

My friend grew up with someone who had become blind at a young age and also taught himself to do the echolocation.  He was even able to ride a bike in the street.  Apparently there were only a few kinds of objects that did not bounce sound well so occasionally he would crash into one of those but most things like cars bounced sound well.  Makes you wonder if nocturnal animals might do this to some extent as well.  Probably it's only in the blind animals like bats that we have thought to look. 

It makes me, again, see how little I've studied/observed others and own being. It encourages me. Thanks, Eva.