Meaning of let out

(verb) express audibly; utter sounds (not necessarily words); "She let out a big heavy sigh"; "He uttered strange sounds that nobody could understand"

make known to the public information that was previously known only to a few people or that was meant to be kept a secret; "The auction house would not disclose the price at which the van Gogh had sold"; "The actress won't reveal how old she is"; "bring out the truth"; "he broke the news to her"; "unwrap the evidence in the murder case"; "The newspaper uncovered the President's illegal dealings"

bring out of a specific state

make (clothes) larger; "Let out that dress--I gained a lot of weight"