The Complete Thief's Handbook[]
Recommended: Bandit, Bounty Hunter, Smuggler.
A character with this proficiency is capable of imitating noises made by various animals. A successful proficiency check means that only magic can distinguish the noise from that of the actual animal being imitated. A failed die roll means that the sound varies from the correct noise in some slight way.
If the die roll fails, this does not mean that all creatures hearing the noise know that the sound is fake. While creatures and humanoids that are very familiar with the noise know this automatically, other creatures or characters in earshot may require Wisdom checks to determine if they detect the fake.
Bandits and Smugglers often use this ability for communication on the job, almost as a variant dialect of thieves' cant.
The Complete Book of Humanoids[]
A character with this proficiency can imitate the noises made by various animals. A successful check means the character's noise cannot be distinguished from that of the actual animal, except by magical means.
A failed check produces a sound that varies from the animal's in some slight way. Those who are very familiar with the animal will recognize the intended mimicry at once. Other characters must make successful Wisdom checks to determine if they also realize the animal noise is an imitation.