The first known animation to use synchronized sound was Dinner Time (1928) by Paul Terry.
It has been called the most significant cartoon in animation history that no one has ever seen. It was one of the few synchronized sound cartoons produced before (though released after) Walt Disney’s Steamboat Willie. It played a small but pivotal part in Walt Disney’s creation of his first Mickey Mouse sound cartoon. It was this film, shown to Walt in New York on the cusp of recording his track for Steamboat Willie, that gave him the confidence to press on with his plans.
Dinner Time (1928)