A vocalization was a sound made by a lifeform to communicate. Examples included barking (dogs), bird calls (birds), hissing, purring, and meowing (cats), and roaring (Klingon females).
Data was able to distinguish between three hundred different vocalizations. In 2370, he mentioned this when Jean-Luc Picard heard what sounded like an animal calls on the USS Enterprise-D. Picard noted that Worf, while suffering from Barclay's Protomorphosis Syndrome, was making angry, aggressive sounds, and speculated that the apparently devolved Klingon might be attempting to scare off other predators, mark his territory, or commence the mating process. (TNG: "Genesis")
Notable examples
Coo
A coo was a soft sound made by pigeons.
In 2374, a holographic Leonardo da Vinci remarked to Kathryn Janeway that he only heard the cooing of pigeons and the babbling of fools in Florence. (VOY: "Concerning Flight")
Screaming
In 2268, Captain James T. Kirk asked Odona about her homeworld, and she said she did not remember. She also said, "I was standing in a large auditorium crowded with people. Thousands pressed in against me. I could hardly breathe. I was fighting for oxygen, screaming to get out." (TOS: "The Mark of Gideon")
Squeal
In 2269, the squealing of rats was part of Flint's memories of Constantinople in 1334. (TOS: "Requiem for Methuselah")
In 2371, Neelix mentioned the agonized squeals of a two-tailed talchok after he had trapped it on Rinax. (VOY: "Jetrel")
In 2401, among the sounds Vadic recalled from the Project Proteus laboratory was "the squealing of wheels down a hall." (PIC: "Dominion")