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NFPA 72 Increases Emphasis on Intelligible Voice-Evacuation Systems

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Since the early 90’s, I’ve been helping architects create large spaces with good acoustical environments. What is a good acoustical environment… and why has NFPA 72-2010 changed things?

A good acoustical environment is, quite simply, an environment that supports the function of the space. One consideration when determining the appropriate acoustical environment is sound reinforcement/reproduction system performance. I think that it is obvious to most people that the acoustical environment in a church or auditorium must accommodate quality sound reinforcement and sound reproduction over the house audio system. It may be less obvious to some that the acoustical environment is equally important in a large space that has an overhead paging system. Airports may be the most obvious example. Airports and other transportation terminals often have large spaces and their overhead paging systems convey critical information. It is imperative that speech from these systems be intelligible to passengers. For many years, I and other acoustical engineers have been helping to ensure that HVAC systems were sufficiently quiet, that reverberant noise buildup caused by passenger activity was limited, that intruding noise from aircraft was acceptable, and that sound reverberation times were not too long. We used computer software to model the acoustical environment and the paging system. We carefully selected paging system loudspeakers, using, where necessary, more directive overhead models, columns, or, more recently, phase array speakers. Methods for predicting and measuring paging system speech intelligibility have been in use for many years. For the most part, all of this analysis and careful design has not been applied to emergency evacuation systems, systems which simply sounded an alarm. The only tie to the overhead paging system was for silencing the paging system when the alarm sounded. With the 2010 publication of NFPA 72, this is bound to change.

For the first time, the Agent Having Jurisdiction (AHJ), or local fire marshal, may require that an intelligible voice-evacuation system be installed in public gathering spaces that accommodate more than 300 people and may require system commissioning to confirm that the CIS 0.70 speech intelligibility requirement is achieved. Acoustical engineers will now be able to bring their skills to the design of these voice-evacuation systems and the spaces that they serve. In fact, it would be unthinkable to design one of these systems for a large gathering space without the assistance of an acoustical consultant.

There will be another result of these changes to NFPA 72. There have in the past been a limited number of loudspeakers and paging system components which met the NRTL life safety (formerly UL) requirements. The limited number of approved loudspeakers and components available to designers meant that it was difficult to design intelligible emergency voice communication systems for large spaces. It should now become easier as more manufacturers start offeringt products meeting the NRTL life safety requirements.

If you need assistance with design, modeling, or commissioning one these systems, you can contact me at Soundscape Engineering LLC (