Related Clues:

• "Be still!"
• 'Keep quiet!'
• Where work piles up ... with a hint to this puzzle's theme
• Theatregoer's reproof
• 'Lower your voice!'
• "Lower your voice!"
• Hospital reminder, perhaps
• Stereotypical librarian admonition
• 'I'm trying to work here'
• Vocal calmer
• Sound aptly hidden in "hush-hush"
• Movie theater reprimand
• Moviegoer’s reprimand
• “Quiet!”
• Fricative admonishment