For public buildings (shopping malls, schools, train stations, airports, stadiums), voice alarm speech intelligibility must be verified by objective measurements per EN 50849 and IEC 60268-16.
Mandatory STI Thresholds in Acoustically Different Areas (ADA)
- Average STI: Across 90% of each ADA, average speech intelligibility must be STI ≥ 0.50 (equivalent to CIS ≥ 0.70).
- Minimum STI: No individual point may fall below STI = 0.45.
- Obsolete RASTI removed: RASTI is no longer permitted under Edition 4/5 of IEC 60268-16. Full 7-octave-band STIPA (125 Hz – 8 kHz) as implemented in the Bedrock SM50 / SM90 is required.