Which of the following is listed as an unusual sound type on walls or doors?

• A. Banging on walls/doors/tables
• B. Footsteps
• C. Laughter
• D. Whistling

Answer: (A)

Listen for signals that clearly indicate disruption or potential tampering. Banging on walls, doors, or tables is the unusual sound because it involves forceful, purposeful contact that draws attention and suggests someone trying to break through or alert others. The other sounds—footsteps, laughter, and whistling—are common in many environments and don’t inherently indicate an unusual disturbance on a wall or door. So, banging stands out as the unusual sound type to notice and respond to.