You walk toward the odd sound. Something is moving through the forest nearby. You’re not sure if it’s friendly or hostile. You feel it’s best to sneak up and see what it is instead of announcing your presence.
To creep through the forest toward the sound, you’ll use the sneak skill. Like search, it’s a Perception skill. The dice score for your sneak is 3D. Roll 3 dice and add them up to see how good you are at slipping silently through the forest.