The document discusses new requirements for voice communication systems in buildings according to the 2010 National Building Code of Canada (NBC). It requires a voice communication system be installed in buildings over 1000 occupants that have a 2-stage fire alarm system. The system must use loudspeakers to broadcast prerecorded, synthesized, or live messages with a Common Intelligibility Scale (CIS) of at least 0.70, corresponding to 80% word and 95% sentence intelligibility. Factors like signal-to-noise ratio, distortion, and reverberation can impact intelligibility. Proper speaker layout and coverage is important for design. The document provides an overview of measuring and testing intelligibility.