SVC on Twitter    SVC on Facebook    SVC on LinkedIn


Say What? Intelligibility in the Spotlight

Mass notification systems are part security, part fire safety, and (increasingly) part AV. And while life safety and AV systems don't typically interoperate, forthcoming code changes by the National Fire Protection Association may change that, creating opportunities for AV professionals and security contractors to collaborate and follow new guidelines that could eventually save lives.

A suspected gunman is on campus–stay in the classroom. A tornado is coming–proceed to the nearest shelter. When such warnings reflect actual emergencies, they must reach as many ears as possible to guide people to safety. Mass notification, a term coined by the U.S. government in a 1997 report, has become a crucial means for doing so. But until recently, such systems were underscrutinized and little attention was paid to a fundamental characteristic that should define their effectiveness–intelligibility.

Feature-Inteligibility-Main(300)Mass notification systems are part security, part fire safety, and–increasingly–part audiovisual. And while life safety and AV systems don't typically interoperate, forthcoming code changes by the National Fire Protection Association (NFPA) may change that, creating opportunities for AV professionals and security contractors to collaborate and follow new guidelines that could eventually save lives.

The 2010 version of the NFPA 72 code, also known as the National Fire Alarm and Signaling Code, adds new provisions for mass notification systems, plus important requirements for achieving and testing voice intelligibility. In other words, the code now requires that people be able to not only hear verbal instructions in an emergency (audibility), but also to understand them (intelligibility).

"Much of the driving force for NFPA 72 code changes are from the military. In 2002, it was mandated that every Department of Defense facility have mass notification by 2008," says Bill Sako, chairman of Sako & Associates, a security and AV technology consultancy based in Chicago. "After catastrophic events like 9/11, Hurricane Katrina, and the Tube attacks in London, there was even more of a need for mass notification systems in public spaces that were both audible and intelligible."

Audio professionals have spent years trying to influence the NFPA code to benefit their clients, which often run public address solutions that AV contractors install in addition to the life safety notification systems they're required to have. In fact, the National Systems Contractors Association (NSCA) was involved in the original code-making panel on intelligibility.

"From 1995 to 2002, we sponsored three subject matter experts to work on intelligibility standards on the NFPA Technical Correlating Committee on Signaling Systems," says NSCA executive director Chuck Wilson. "In the 2010 changes, intelligibility is in the body of the code, not a footnote. There's also a chapter on circuits and pathways and a revised intelligibility-testing chapter. The audio influence on the NFPA 72 code is coming to fruition and reflects our work over the past 10 to 15 years."

Morris Stoops, global product leader for notification and computer-based solutions for GE Security, says, "It is the biggest life safety change in decades. NFPA 72 is like the Bible to life safety professionals. In 2010, the title is changed to add 'signaling' as part of the code. Now mass notification is allowed to override the fire alarm system, which used to be top dog. No one was ever allowed to override the fire alarm in the past."

AV and Life Safety Intersect

Though the code's impact is significant, its effects won't be felt immediately. The 2010 NFPA 72 code is final and available for people to download and study, but it won't be enforceable until October 2010, and even then only in jurisdictions where it will be adopted. There is no law or mandate that requires a jurisdiction to use the most current year's code. A town or city can use a code from as far back as 2000, so it is important to verify code versions when starting a project that touches life safety and emergency notification systems. Still, experts have already begun discussions with contractors and building owners to prepare for possible code changes.

Under NFPA 72 version 2010, a notification system can pass intelligibility testing in one of two ways–objective or subjective testing. For objective testing, the system must score a 0.5 or better reading on the speech transmission index for PA systems (STIPA) index. Objective testing is the preferred method for testing under NFPA 72 and the criteria for setting up the test is outlined in Appendix D of the 2010 code.

Subjective testing is based on the ANSI S3.2-1989 standard, which outlines how a five-person panel listens to a library of phonetically balanced (PB) word lists read by five speakers (chosen for their good pronunciation). The number and selection of PB words is determined by the tester. Listeners respond to each word by writing down the word they hear. Once a percentage of understanding is established by the listener panel, the subjective result is then statistically adjusted for biases in the environment, such as background noise. Pass/fail criteria is determined by the tester, which is to say there is no universal threshold of understanding that applies to all systems tested under NFPA 72-2010.

"This is a forward-looking code that is not retroactive to older buildings, but building owners may want to renovate to the new code," says Wilson. "We are at the start of the compliance aspect of the process. It may take one to two years to have it fully understood and implemented."

NSCA is cooperating with NFPA and other related industry associations to promote awareness of the code revisions. NSCA is also developing training for architects, engineers, and integrators. For AV professionals, the new NFPA code represents an opportunity to meet with business partners and clients to educate them about code changes and develop solutions, but because the newest provisions require the expertise of multiple contractors, adoption of the 2010 code could take time.

"Everyone is used to working in silos rather than on a collaborative design basis," says Sako. "There are lots of revelations in the 2010 code in terms of intelligibility. We expect pace-setters will adopt the 2010 code and there will be a domino effect."

In venues such as airports, which already have good intelligibility built into their PA systems, the bulk of new integration work will be in establishing pathways to and from the PA and emergency systems. "The goal is code-compliant interoperability between life safety and PA systems," explains Wilson. "Today, you may only hear the alarm and vocal instruction through the 4-inch speaker installed next to the flashing strobe. After these code changes, the PA system becomes part of the emergency system for notification and instruction."


Intelligibility requirements should help bridge the interoperability gap between a building's life safety alert systems and its overhead public address systems (pictured)

Sako says that for audio designers, the integration means adding another input for digital signal processing, but also for an interface that can handle overrides. Ultimately, the NFPA 72-2010 code may prove a revelation to life safety contractors as they realize intelligibility requires people who understand audio.

"Pro audio quality is much better than that of fire voice evacuation systems," says Sako. "Because of the new fire safety standards that require intelligibility, fire safety designers will now understand why for years pro audio integrators have been using three to five times the number of loudspeakers in similar spaces. The new code change is recognition of higher quality design skill and means that audio pros could be asked to get into areas of a building they haven't touched before."

Already, life safety manufacturers like GE Security are adopting sound modeling programs such as EASE and Bose Modeler, which is new technology to life safety contractors. Stoops says GE Security is in the process of gathering modeling data for its products to make it easier for integrators to design mass notification systems with GE Security gear. "The change in life safety is that audio systems are engineered up front, which is a new way of thinking for us," says Ted Milburn, fire product marketing manager for the Americas for GE Security. "Audio pros understand the perception and intricacies of sound and how to install systems that are intelligible with even coverage."

Another way in which AV integrators will exercise more leverage in design and installing mass notification systems is in collaboration with building architects. The new NFPA code will inevitably affect the number and placement of speakers, limiting an architect's ability to hide them. Audio pros are most likely to help develop solutions that balance aesthetics and intelligibility. "Life safety systems need to pass inspection to get the certificate of occupancy," says Stoops. "If the speaker is hidden and it affects intelligibility, then it won't pass. Life safety was always a back-of-the-house system, but mass notification now means a truly integrated building."

Stoops, who is also chairman of the UL 2572 Interfaces Subcommittee, says the group is in the process of defining multiple interface standards so that fire safety systems can interoperate with paging and other notification systems. Currently, the de facto standard for fire safety systems are a UL 1480-listed speaker, a UL 1971 clear strobe, and a UL 1638 amber strobe.

"The UL interface standard will remove any concern that connectivity to other systems will not damage a component. Paging speakers, for example, will have to conform to NFPA 72 and a UL 2572 interface listing," explains Milburn, who has been traveling the country with Stoops educating contractors about the changes.

Testing for Intelligibility

While NFPA authors the code, it doesn't enforce it. Code enforcement is handled by so-called authorities having jurisdiction (AHJ), which can be the fire marshal, fire chief, or other fire safety official in a given city or town. As it is, the life safety market is extremely regulated, with pre-testing and testing documentation required for approval. Life safety system testing is done at a minimum of once a year.

With the new code AHJs are also in charge of testing the system for intelligibility and audibility, though an AV integrator with expertise in audio may also run the intelligibility tests under the supervision of an AHJ. According to Wilson, there is an 83-page intelligibility testing protocol outlining indoor and outdoor methods. A speech intelligibility meter is also required for testing.

NSCA, GE Security, Bose, Gold Line, and Simplex were among several organizations that were integral to establishing the testing protocol. "We went to real-world sites for testing, such as an office building, a commercial manufacturer, and a large shopping mall," says Stoops. "The mall was very reverberant and had three systems–fire alarm, commercial paging, and sound reinforcement. We connected the audio sources with a talk box that produces the STIPA signal (a composite frequency of the human voice) and tested for intelligibility."

In large and acoustically challenging places, the 2010 NFPA 72 code allows the sound designer to designate acoustically definable spaces (ADS) whose boundaries must be documented for the AHJ prior to testing. Typically each ADS is defined by where people travel through the space, and each is tested for intelligibility.

This model could apply to spaces like a grand lobby that is mostly marble and glass–a very reverberant environment where one might not expect good intelligibility. Such a lobby might not pass code under the 2010 version, but in theory, if a sound designer can break up the lobby into multiple ADSes, the building has a better chance to pass.

Overall, life safety may end up looking more like an AV installation, and the expertise that an AV integrator brings to the project could mean the difference between a building that passes fire code and one that doesn't. A 2008 report by the Fire Protection Research Foundation stated, "The fire alarm community has traditionally had a different design focus than acoustic systems designers (i.e., public address or music systems), and the advent of a test protocol may require a transformation of the industry to a higher quality in terms of how these systems are designed."

"If that mall failed to pass the new code, the facility manager is responsible for a plan to update the systems," say Stoops. And that would require pro audio experience. "There is a big realization in our industry that grandfathering is no longer an excuse to shield against a code update."

Especially now that life safety has taken a page out of sound design principles.

Linda Seid Frembes is a freelance AV writer and contributing editor to Pro AV.

Browse Back Issues
  January 2015 Sound & Video Contractor Cover December 2014 Sound & Video Contractor Cover November 2014 Sound & Video Contractor Cover October 2014 Sound & Video Contractor Cover September 2014 Sound & Video Contractor Cover August 2014 Sound & Video Contractor Cover  
January 2015 December 2014 November 2014 October 2014 September 2014 August 2014