A siren tells people something is wrong. A voice evacuation system can also tell them what to do and where to go. That is valuable in hospitals, malls, schools and large offices, where people may not know the building or may need to leave in stages.
Intelligibility comes first
A loud message is not automatically a clear one. Hard surfaces, long reverberation and background noise can make speech difficult to understand.
Designers commonly measure this with the Speech Transmission Index, or STI, defined in IEC 60268-16. Many specifications set a target of about 0.50, but the required value depends on the applicable standard and the authority having jurisdiction. Check it for your project and verify it on site after installation.
What separates it from ordinary paging
- Priority: emergency messages override music and routine announcements.
- Monitoring: the system reports faults in amplifiers, lines and key components.
- Backup power: batteries keep it running for the required period.
- Survivable wiring: cable routes and types are designed to keep working for the required time during a fire.
- Fire alarm link: an alarm can trigger the correct message in the correct zone.
Standards often used in specifications include the EN 54 series for equipment and BS 5839-8 for system design, among others. Your fire consultant should confirm which apply.
Plan the evacuation before the speakers
The zone plan should follow the building's evacuation strategy. Will everyone leave together, or will floors leave in phases? Who may make live announcements? Which pre-recorded messages are needed, and in which languages?
Keep testing it
Evacuation systems need routine checks, recorded maintenance and repeat testing after renovations, because new finishes and layouts change how speech carries. Our article on acoustic design explains why rooms affect clarity so much.
