Please lower your voice.
la PREH-goh dee ab-bas-SA-reh la VOH-cheh.
When a fellow audience member is talking too loudly during the performance. Italian theatre etiquette is strict — the formal register here signals seriousness.
La prego is the very polite formal 'I beg you' or 'please', using the formal lei form. Di abbassare means to lower. La voce means the voice. This phrase is polite but firm — more forceful than just saying 'shhh'.
Silenzio, per favore.
Silence, please.
Direct and clear, less formal but effective.
Per cortesia, si può stare in silenzio?
Please, could you be quiet?
Polite question form.
Sta disturbando gli altri spettatori.
You are disturbing the other audience members.
More assertive — states the effect of the behaviour.
Italian opera audiences are generally knowledgeable and respectful, but they can also be very vocal in their enthusiasm. Talking during the music is considered very rude (maleducato). The loggionisti, however, famously shout 'bravo' during and after arias — a traditional form of audience participation.