and the blind shall see.......

I have a musician friend, David. He's blind. The interesting thing is although he can't see he is very aware of his surroundings, we were walking down the road and HE says to ME "Mind that bush."
"What? How the hell did you know that?"
"I could see it."
"David! Hello! You're blind."
"Yeah but this is a different way of seeing....." and he explained to me how he sees. It goes like this..............

Imagine you've been blindfolded and taken into a room, if the room is completely empty you will hear the echo of your footsteps. From that echo you can just about imagine how big the room is. If it's a fully furnished room the echo will be seriously muffled and you can judge by that too. So without even realising it you've already got some sort of blindfolded vision. Now take that a few stages further. You are outside and you've got traffic noise and your own footsteps and voices all echoing around you, by moving your head you can zone in on various sounds. David tells me he can tell the difference between a bush and a Mail box by it's sound.
Completely bleedin amazing.
The only thing that worries me about his claim is that in the pub he can't tell which way the bar is when it's his round...... Hmmmmm!