Sound: Ok, I didn't believe what I read that your brain can tell the direction of sound because one ear hears it first, I thought it was just volume. I mean detecting 2/3rds of a millisecond?! But I proved myself wrong - if you load your favourite piece of music into Audacity (a free sound editor), you can delay one channel (I delayed it by 0.68ms, the time taken for speed to travel the distance between my ears). Now listen through headphones. Although the same volume is in each ear (easily proved by pulling one earphone out), it sounds like it's entirely in one ear. Volume has the same effect, if I then made the other side 6dB louder, it went back to sounding like it was in the centre. I wonder why your brain uses both timing and volume?
Smell: This I can't believe though, and I don't know how to prove it except by experience. If you walk into a room, you have no idea which way a smell is coming from, yet I've read claims that you sense the smell through each nostril seperately and time it. A dog maybe, but surely not a human. I've never been able to work out where a smell is coming from without moving around the room and sampling different parts of it.