With a DC 5 Perform (wind instruments) check you can use a whistle to signal the same sorts of situations as signal horns. A whistle's piercing report can be clearly heard (Perception DC 0) up to a quarter-mile away. For each quarter-mile beyond, Perception checks to hear a whistle suffer a –2 penalty.
Silent whistles that only animals and other creatures with keen hearing can hear also exist.
- Advanced Player's Guide
- Adventurer's Armory
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