Billboard:
For context, sound trademarks are extremely rare. According to [a law review article], there are more than 2.6 million active trademark registrations in the United States. Of those, there are only about 250 active sensory trademark registrations. Of those, about 234 are sound trademarks, and of those, about 36 are "familiar sounds," or sounds without words, yet associated with a particular good or service.Miami Herald:
To obtain Pitbull’s grito trademark, his legal team had to persuade the USPTO that his yell is so closely associated with the artist, that even if his name is not uttered, or he isn't present, people automatically think it's him.
...
At least part of the motivation behind trademarking “EEEEEEEYOOOOOO” stems from a similar grito heard in J Balvin and Willy William’s hit “Mi Gente.”
The article defines a grito as “a loud shout of joy or excitement that is commonly associated with Mexican culture,” one Pitbull started using as early as 2002 in Miami clubs (to alert his friends that trouble might be escalating).