Field Story
The Dome That Made the Imam Speak Twice
A mosque with a 14-meter dome created a strong acoustic focus point 8 meters from the mihrab, causing worshippers to hear the imam twice with a 120 ms delay. Impulse response measurement clearly showed the focused reflection. Applying diffusive panels to the lower dome surface and a thin absorptive layer at the focus zone reduced the reflection by 14 dB, restoring clarity.
MosquePhase Analysis per ISO 3382-1
TL;DR
Phase analysis provides additional insight into room acoustic behavior alongside the standard ISO 3382-1 parameters derived from the impulse response. The phase response of the room transfer function reveals modal behavior below the Schroeder frequency, where each room mode has a characteristic phase signature. By analyzing phase at different positions, you can identify degenerate modes, modal coupling, and the transition from modal to statistical room behavior. SonaVyx phase display in the transfer function view complements the standard ISO 3382-1 impulse response analysis with frequency-domain phase information.
Phase in Room Acoustics
Room modes are resonances with specific phase relationships. Below the Schroeder frequency, the room response is dominated by individual modes, each with a 180-degree phase shift through resonance.
Modal Phase Signatures
- Each room mode appears as a magnitude peak with a corresponding 180-degree phase rotation
- The rate of phase change through the mode relates to its Q factor and decay time
- Overlapping modes create complex phase patterns that indicate modal coupling
- Above the Schroeder frequency, phase becomes pseudo-random (statistical region)
Spatial Phase Variation
- Phase varies significantly with position below the Schroeder frequency
- At nodal positions, phase flips 180 degrees compared to adjacent antinodes
- This spatial variation explains why RT60 can differ between positions at low frequencies
- Phase data at multiple positions maps the modal structure of the room
Source Verification
ISO 3382-1 requires an omnidirectional source. Phase should be consistent across different measurement angles. Large phase variations between angles indicate directional source behavior.
Common Mistakes
- Interpreting random phase variations above the Schroeder frequency as meaningful
- Not recognizing modal phase patterns at low frequencies
- Comparing phase between positions without accounting for propagation delay
SonaVyx Workflow
View phase in the SonaVyx transfer function. Capture IRs with the IR tool. Measure RT60 with the RT60 tool. Check levels with the SPL meter. Predict room behavior at AcousPlan. See our learning modules for room acoustics theory.
Standard Reference
ISO 3382-1:
Try It Now
Open this measurement tool in your browser — free, no download required.
Last updated: March 19, 2026