Noisemaker Arrows
From The DarkMod Wiki
Noisemaker arrows are used as distractions, to get guards to go somewhere else. A guard that hears a noise arrow will immediately go alert (but not enough to be certain of an intruder), and start heading towards the arrow location.
In-game description
Noisemaker arrow: These noisy clockwork devices are used by thieves and assassins to create a temporary diversion.