Emergency Evacuation PA Testing: STI Compliance

Regulatory Requirements

Standard	Requirement	Test Method
EN 54-16	STI ≥ 0.50 all positions	STIPA per IEC 60268-16
BS 5839-8	STI ≥ 0.50 (0.45 under balconies with additional visual alert)	STIPA
NFPA 72	Intelligible throughout (no specific STI value in code)	Audibility: 15 dBA above ambient or 5 dBA above max ambient

Test Procedure

1. Plan measurement positions. Test at: the farthest point from any speaker, under balconies and mezzanines, in corridors and stairwells, at emergency exits, and in areas with high ambient noise (plant rooms, kitchens, loading bays). EN 54-16 specifies testing at the most acoustically challenging positions.
2. Measure ambient noise first. At each position, record the LAeq for 1 minute with the emergency PA off. This documents the noise condition during testing. Ambient noise correction is applied per IEC 60268-16.
3. Generate STIPA signal. Use SonaVyx STI tool to generate the IEC 60268-16 compliant STIPA test signal. Route this into the emergency PA system's voice message input (replacing the normal voice message with the test signal).
4. Set PA level. The emergency PA should operate at its designed level — do not increase or decrease from the as-installed setting. The test measures the system as occupants will experience it.
5. Capture STIPA at each position. Use Pro mode (3 averaged measurements) for compliance testing. Record the STI value, the measurement position, ambient noise level, and any notes about conditions.
6. Document results. Generate a Technical Commissioning report showing: system description, measurement positions (marked on floor plan), ambient noise levels, STI results per position, pass/fail assessment per EN 54-16, and engineer's signature.

Common Reasons for STI Failure

• Excessive reverberation. RT60 above 2.0 seconds degrades STI below 0.50 regardless of speaker quality. Treatment or directional speakers are needed.
• Insufficient speaker coverage. Dead zones between speakers or behind structural columns receive inadequate direct sound. Additional speakers needed.
• High ambient noise. Plant rooms and kitchens often exceed 70 dBA ambient. The PA must overcome this noise at the critical 1-4 kHz speech range.
• Speaker placement too high. Ceiling-mounted speakers at 6+ meters create long reverberant paths. Closer, more numerous speakers at lower height improve STI.

Tool Bridge

Run STIPA testing with the SonaVyx STI Tool. Document ambient noise with SPL Meter. Generate compliance reports with Report Generator.