What should the loudness of audible public warnings be according to NFPA 72?

• A. 12 dB above ambient
• B. 18 dB above ambient
• C. 15 dB above the average ambient sound level
• D. 25 dB above ambient

Answer: (C)

NFPA 72 requires audible public warning signals to be clearly audible above typical background noise. The standard specifies that the warning signal level must be at least 15 dB above the average ambient sound level at occupant locations. This margin helps ensure the message is both audible and intelligible in spaces with varying noise, without being unnecessarily loud. If the level were only 12 dB above ambient, it could be masked by background noise; higher margins like 18 dB or 25 dB are not required and can be overly disruptive. So the correct requirement is 15 dB above the average ambient sound level.