Phase Analysis per IEC 60268-16

TL;DR

Phase response of the PA system affects speech intelligibility by influencing how different frequency components arrive at the listener. While IEC 60268-16 STI primarily measures modulation preservation, severe phase distortion can indicate system problems that also degrade modulation transfer. Group delay variations cause temporal smearing of speech consonants, and phase cancellations between multiple speakers create frequency-dependent nulls that reduce per-band STI. SonaVyx phase analysis helps identify these system-level issues that standard STI measurement alone may not diagnose, providing actionable information for improving speech clarity.

Phase and Speech Clarity

Speech intelligibility depends on preserving the temporal structure of consonants and vowels. Phase distortion in the PA system can smear these temporal features, reducing the modulation depth measured by STI.

Group Delay and Consonant Clarity

Consonants are short, high-frequency transients that require minimal group delay variation
Group delay exceeding 20 ms in the 2-4 kHz range can smear consonant attacks
FIR-based crossovers can achieve linear phase (constant group delay)
IIR crossovers introduce frequency-dependent delay that varies through the crossover region

Multi-Speaker Phase Interaction

Where speaker coverage zones overlap, phase differences create interference patterns
These patterns cause frequency-dependent level variations that affect per-band STI
Phase alignment between zones is as important as level matching for STI uniformity
Measure phase at overlap zone positions to verify alignment

Phase and Reverberation

In reverberant spaces, the room adds energy with random phase. This decorrelated energy reduces coherence and MTF. Phase analysis of the direct sound versus total response helps distinguish system phase problems from room reverberation effects.

Common Mistakes

Ignoring phase when troubleshooting poor STI results
Not checking phase alignment in speaker overlap zones
Confusing phase problems with polarity inversion

SonaVyx Tools

Analyze phase with the SonaVyx transfer function. Measure STI with the STI tool. Check polarity with the problem detector. Verify levels with the SPL meter. Get AI recommendations from the diagnostic engine. Follow the PA tuning workflow.

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