I have a friend who is blind. He can walk through a room full of furniture and miss most of it. He says he can hear where the furniture is. Well, he describes it as he can hear where the furniture is not because of the echos. He has best success in a house with hardwood floors. He still taps around with his cane until he knows the layout of the room in his mind, but he gets around pretty good in a room that is strange to him.
And think about it, the Falmer have been living in Dwarven ruins for ages upon ages. Generations have grown up in them, they know them like the back of their hands, couple that with their hyper sensitive hearing and they could easily fire an arrow in the general direction you're in.
If you try it yourself for a while, you get a small taste of what it would be like to rely on other senses, I can quite easily tell the general direction of a sound without actually opening my eyes, think what a creature with hyper sensitive hearing could tell from a sound.