be quiet
A command to stop talking or making any noise. Often (but not exclusively) said as a harried imperative. Be quiet! Do you want them to hear us? Kids, please be quiet—your mother has a headache.
Be quiet!
Stop talking or making noise. (Regarded as a bit harsh or overbearing, but made polite with please.) Bill (entering the room): Hey, Tom! Tom: Please be quiet! I'm on the phone. Tom: Hey, Bill! Bill: Be quiet! You're too loud. Tom: Sorry.