Please lower your voice.
Stress 'ab-BAS-si'. 'Si abbassi' is the formal imperative of 'abbassarsi'.
A librarian or another user might say this to you. You might also need to say it politely to someone speaking too loudly near your study area.
'Si abbassi la voce' = lower your voice (formal imperative, Lei form). 'La voce' = the voice. More directly: 'Silenzio, per favore' (Silence, please). Italian libraries post rules ('regolamento') that typically prohibit loud talking, mobile phone calls, and food.
Qui è zona silenzio.
This is a silent zone.
Pointing out the rule.
È vietato parlare a voce alta.
Loud talking is prohibited.
Stating the prohibition.
Per favore, non usi il telefono qui.
Please don't use your phone here.
Requesting phone silence.
Italian library silence rules are taken seriously in institutional settings but enforcement can vary. In university libraries, a culture of peer-enforced silence ('rispetto reciproco') is generally strong. Italian library signs often use 'Zona silenzio' or 'Rispetta il silenzio' rather than a simple 'No talking' sign.