Can be done super early in the game (it was actually my second trophy overall). What you will want to do is use crouch (
) to limit your sound and sneak up behind a machine. You could also wait, while crouched, in some tall grass for a machine to approach you.
Once close enough, you will see a prompt at the bottom of the screen to press
to perform a silent takedown. Simply repeat this process on 10 machines throughout the game and you'll add another bronze trophy to your PSN ID.