What are the sound level requirements for audible appliances in sleeping areas according to NFPA 72?

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Question​

What are the sound level requirements for audible appliances in sleeping areas according to NFPA 72?

Answer​

According to NFPA 72, audible appliances installed to provide signals in sleeping areas must meet specific sound level requirements to ensure they can effectively wake occupants. Here are the key requirements:

Requirements​

18.4.6.1When installing audible appliances in sleeping areas, they must produce a sound level that is either:

• At least 15 dB above the average ambient sound level, or
• 5 dB above the maximum sound level with a duration of at least 60 seconds, or
• At least 75 dBA, whichever is greater.

This sound level should be measured at pillow level using the A-weighted scale (dBA) to ensure it is loud enough to wake someone sleeping.

18.4.6.2If there is any barrier, such as a door, curtain, or retractable partition, between the notification appliance and the pillow, the sound pressure level must be measured with the barrier in place. This ensures the sound can still effectively reach the sleeping person despite any obstructions.

Additional Considerations​

Even though the requirement in 18.4.6.2 specifically applies to sleeping areas, it is good practice to use the worst-case conditions for all ambient and alarm sound level measurements. This means testing with barriers like doors both open and closed to ensure the required sound levels are met in both situations.

The sound reduction through a bedroom door can vary based on its construction and fit. In some cases, achieving the required 75 dBA sound level inside the bedroom with an appliance located outside the room may not be possible. In other cases, it might be achievable, but the sound level near the audible appliance could exceed the maximum permitted 110 dBA as per 18.4.1.2.

To ensure the effectiveness of audible alarms in sleeping areas, NFPA 72 requires that these alarms be significantly louder than the surrounding noise, taking into account any barriers that might affect sound transmission. This helps ensure that alarms can wake occupants even in less-than-ideal conditions.

 

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2021 IBC has additional requirements

[F] 907.5.2.1.3.1 Fire alarm system signal.​

In sleeping rooms of Group R-1 and R-2 occupancies, the audible alarm activated by a fire alarm system shall be a 520-Hz low-frequency signal complying with NFPA 72.
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[F] 907.5.2.1.3.2 Smoke alarm signal in sleeping rooms.​

In sleeping rooms of Group R-1 and R-2 occupancies that are required by Section 907.2.8 or 907.2.9 to have a fire alarm system, the audible alarm signal activated by single- or multiple-station smoke alarms in the dwelling unit or sleeping unit shall be a 520-Hz signal complying with NFPA 72. Where a sleeping room smoke alarm is unable to produce a 520-Hz signal, the 520-Hz alarm signal shall be provided by a listed notification appliance or a smoke detector with an integral 520-Hz sounder.