IEC 60268-16: STI Reporting and Compliance Documentation
TL;DR
IEC 60268-16 Clause 7 specifies reporting requirements for STI measurements. Reports must include: measurement method (direct STI, STIPA, or IR-derived), test signal type and level, ambient noise conditions, PA system settings (gain, EQ, zones), measurement positions (plan/drawing), equipment used with calibration status, per-position STI values, spatial average and standard deviation, and the applicable quality threshold. For EN 54-16 compliance, a zone-by-zone pass/fail matrix is required. The report should state whether the masking model was applied and which edition of the standard was used.
Minimum Reporting Requirements (Clause 7)
A compliant STI measurement report must document:
- Method: Direct STI, STIPA, or STI from impulse response
- Test signal: Type, level at the PA system input, and playback configuration
- PA system state: Gain settings, EQ, zone configuration, AGC/limiter status
- Ambient noise: LAeq during measurement, description of noise sources, whether HVAC was running
- Equipment: Microphone model, analyzer model/software, calibration date
- Positions: Plan drawing showing source and receiver locations with coordinates
- Results: STI per position, spatial mean, standard deviation
- Standard edition: IEC 60268-16 Ed.5 (2020) — results from different editions may not be comparable
EN 54-16 Compliance Format
For emergency voice alarm systems, the commissioning report typically includes:
| Zone | Positions measured | STI min | STI max | STI avg | Pass/Fail |
|---|---|---|---|---|---|
| Zone A - Lobby | 8 | 0.52 | 0.67 | 0.59 | PASS |
| Zone B - Corridor | 12 | 0.48 | 0.61 | 0.54 | PASS |
| Zone C - Car park | 6 | 0.41 | 0.53 | 0.47 | FAIL |
Each zone is assessed independently. The minimum STI at any measurement position in the zone must meet the threshold (0.50 for EN 54-16), not just the average.
Common Reporting Mistakes
- Reporting only the average: The worst-case position often matters more than the mean. Always report minimum, maximum, and mean.
- Unrepresentative noise conditions: Measuring during quiet periods overstates real-world performance. Document the noise conditions clearly.
- Wrong test signal level: If the PA gain was adjusted for measurement, the STI does not represent actual use conditions.
- Missing masking correction: IR-derived STI without masking correction may overestimate intelligibility in noisy environments.
- Mixing standard editions: Ed.4 and Ed.5 can differ by up to 0.05 STI due to the updated masking model.
Post-Measurement Actions
When positions fail to meet the target STI threshold:
- Add speakers to improve coverage and direct-to-reverberant ratio
- Add acoustic treatment to reduce reverberation time
- Adjust speaker EQ to improve speech band energy (500 Hz – 4 kHz)
- Add delay speakers to improve MTF at distant positions
SonaVyx Report Generation
The report generator creates STI measurement reports including per-position results, zone summaries, floor plan position mapping, and pass/fail assessment against your selected standard. Reports can be exported for client delivery. See measurement procedures for the workflow leading to the report.
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Last updated: March 19, 2026