Falcon Alarms.com : Intelligibility Testing

Intelligibility Testing

Falcon Alarms is proud to announce that we can now do voice intelligibility testing. This testing is required per N.F.P.A. 72 Chapter 4-3.1.5 for final testing of voice evacuation systems and also for yearly maintenance per Chapter 7. The newly developed instrumentation is a technological breakthrough in that many instruments that were needed to perform this test before have been combined into 2 highly portable instruments.

Concern for intelligibility will focus on the specifications for amplifiers and speakers and, as importantly, on individual, job specific system design. Factors such as sound reflections and reverberation will need to be considered in system designs. This will alter the required skill set, not only for system designers and installers, but also for the fire officials who will inspect these installations.

Speech intelligibility is not a physical quantity like Amperes, Volts, or BTU's. It is the degree to which we understand spoken language. Speech is not necessarily intelligible simply because it is audible. Everyone has experienced speech signals that are loud enough but overly reverberant, suffer from echoes or distortion and therefore are not understandable. Announcements in airports, train stations and places of worship often suffer from this problem.

The basics of speech intelligibility, including the factors that affect intelligibility in typical situations are reviewed in a white paper presented at the National Fire Protection Association Congress by Bose® Professional Systems. In addition, the various methods for measuring speech intelligibility are discussed, together with techniques for predicting intelligibility in advance of building construction or equipment installation. Finally, many of the practical considerations fire alarm professionals will face in managing the intelligibility requirement are presented.