While it was long understood to be of Celtic origin, the use of the instrument, made of what appeared to be tubes and a bronze leaf, had remained a mystery.
A similar but much better preserved relic recently found in France allowed archaeologists to realize that the Italian artifact was, in fact, a horn, Italy's ANSA news agency reported Wednesday.
The horns, called carnyxes, were part of a psychological warfare technique, archaeologists said; mixed with the cries of attacking Celtic warriors and the rumbling sounds of their war carts, they helped create a sense of panic in their enemies.
Carnyxes were a type of bronze trumpet, held vertically, with a bell styled in the shape of an animal's head.
Other similar instruments have been discovered in France, Switzerland, Germany and Romania.