What must the loudness of audible public warning signals be?

• A. At least 15 dB above average ambient sound level
• B. At most 5 dB below ambient
• C. Equal to ambient level
• D. No standard required

Answer: (A)

Audible public warning signals must stand out from background noise. Requiring the signal to be at least 15 dB above the average ambient sound level ensures the warning is reliably heard over typical street and environment noise during emergencies. A smaller margin, or being equal to or below ambient, risks the signal being masked by background sounds and going unheard. A standard is needed to guarantee public safety, so the rule is to exceed average ambient noise by 15 dB.