I know I'm looking for something big and heavy. I can guess how it puts its weight on the ground, or I can try listening for the vocalisations it makes.

[ He makes educated guesses. Clark has catalogued everything here. ]

I've had all my life to practice. For example, I've just met you but I could find you in the city from your voice.

[ He could track her heartbeat too but that's a little creepy for a first meeting. ]