leise refers to very little or no sound.

ruhig can mean that as well but it can also mean "calm".

'Ihr' means 'you' plural. The 'all' isn't really there.

The use of "you all" is a confusing choice that the Pearson editors made for sentences in their course when they expect the German second person plural pronoun. Unfortunately, Pearson course sentences are also visible to the general public.

The Pearson sentences will hopefully soon be separated and this confusing usage will be removed.

Until then, take "you all" as a clue that the sentence expects the German ihr as a subject (or euch as an object, etc.), and don't try to translate the word "all" separately.