Translation:The youth like to listen to loud music.
As far as I know, if treated as a collective noun, it's plural. "the youth" can also be one young person.
I think there is a difference between American and British English in this sense. At least for team, group and police, American English treats them as singular, and British English as plural. I don't know about the noun youth. It may or may not be the same.
Funny. I know the word gromki only from two phrases: „gromkie brawa” - loud applause and „gromki śmiech” - loud laughter. Of course there is „grom” itself which means „thunder”.