Related Clues:

• 'Not so loud!'
• 'Keep it down'
• "Keep it down!"
• Piece of pi?
• Usher's admonition
• 'This is a library!'
• Library admonition
• Finger-on-lips sound
• 'Keep it down!'
• Sound necessary to get 'high'?
• Sound necessary to get "high"?
• Admonition to a cell phone user in a theater
• "Stop talking!"
• 'Silence!'
• Request for quiet