There are a lot of factors that need to be considered when designing an emergency communications system. But above all, these systems need to be designed with one goal in mind: getting the message across. No matter what the layout of the facility or the nature of the message, the message needs to be understood by the facility’s occupants. Otherwise, they may not get vital information, or may not be able to take the necessary action in response to the current situation in the facility. In this week’s blog, we’ll talk about the basics of designing an emergency communications system that gets the message across.
The Basics of Designing an Emergency Communications System
Live Speech vs. Prerecorded Speech
Emergency communications systems can utilize either a live speaker or a prerecorded speaker. Generally, prerecorded messages are preferable for a number of reasons. Live speakers can be unpredictable and may unintentionally garble the message. Prerecorded messages can be tested for quality control to ensure that when the time comes, the message will be intelligible.
The acoustics of a room are influenced by a number of factors. In addition to the room’s dimensions, this includes any coverings on the walls, floor, or ceiling, furniture in the room, number of people in the room, and temperature and humidity in the room. Placement of speakers in a room will also affect intelligibility. All of these have the potential to positively or negatively affect the ability of a message to be heard in a space. NFPA 72 standards give guidelines as to designing a space for optimal message transmission, also known as the speech transmission index (STI)
Speech Transmission Index
The STI is on a scale from 0.0 to 1.0. NFPA 72 requires an STI of at least 0.7, in which 95-96% of sentences spoken from an emergency communications system will be understood. Software is available that allows you to input the parameters of your space and generate the potential STI. However, these should only be used if you have a solid understanding of acoustics.
Spaces that may not Require Intelligibility
Spaces that may not require message intelligibility from an emergency communications system include private bathrooms, storage rooms, closets, individual offices, equipment rooms, elevator cars, kitchens, or rooms where intelligibility cannot reasonably be predicted.
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