Amulet of Awakening

This gemstone amulet allows an animal wearing it to speak, even if it is not normally capable of doing so because of its low Intelligence score or lack of known languages. 

That's is possible because of the awakening spell stored inside the amulet, and so, it allows any animals under the amulet's magic to speak. 

However, by taking off the amulet, the animal loses all the effects of the spell.