Measuring intelligibility for fire and emergency communications systems (ECSs) will become more commonplace as local jurisdictions adopt the 2010 version of NFPA 72. Taking proper measures can be complex, and most fire and life safety system designers have to work around existing building features that affect intelligibility.
“A lot of what is in the room itself affects intelligibility, such as what’s on the floor and walls, how big the space is, ceiling height and ambient noise conditions,” says Christa Poss, Marketing Manager for the Audible/Visible Business Unit at System Sensor.
“Speakers are a small part of the overall picture,” adds Poss. Yet, system designers can make the most of speaker choices to maximize sound impact. System Sensor offers a variety of indoor and outdoor speakers that are appropriate for different applications. The SpectrAlert® Advance SP Series speakers, for instance, are best for high fidelity sound output, whereas the SPV speakers are intended to deliver high volume sound output for use in high ambient noise applications.
Fire and life safety system designers can save time and money by installing only as many devices as necessary. To ensure proper coverage without under- or over-designing spaces, system designers can use EASE (Enhanced Acoustical Simulator for Engineers) software to plan their systems (visit www.systemsensor.com/ease). EASE 4.3 software models sound properties for specific environments and speaker configurations. Using the System Sensor speaker data, intelligibility scores and variables, such as room materials, ceiling height and speaker positioning, EASE analyzes the information so system designers can make appropriate decisions.
By plugging System Sensor speaker data into the commercially available EASE software, designers can add or delete speakers and suggest best placement and power tap settings of the speakers.
“System Sensor speakers have four different wattage settings, so the solution may be to add more speakers and tap them lower,” says Poss. Enabling users to run different scenarios with the EASE software to see how system changes impact the intelligibility score is invaluable in determining what is best for each application.
Once the speakers are installed, system designers can use intelligibility meters to read sound conditions and measure the effectiveness of the voice system at multiple locations within each commercial environment.
These handheld meters, says Poss, “take the unknowns away and demystify intelligibility” for building commissioning. During onsite demonstrations, “pink noise,” a type of sound with properties that make it a suitable reference signal for audio engineering, plays throughout the voice system, and the meter predicts the intelligibility score for each location.
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