Field Story
Echo Canyon: When Delay Towers Fight Each Other
A 15,000-seat sports arena installed delay towers at three distances from the stage. Audience members near the second tower heard a distinct echo because the delay was set 28 ms too short. Transfer function coherence dropped to 0.3 in the overlap zone. After measuring propagation delay with the delay finder tool and correcting each tower to within 1 ms, coherence improved to 0.85 and the echo disappeared.
Sports ArenaDelay Finder Measurement per ISO 3382-1
TL;DR
The delay finder supports ISO 3382-1 measurements by precisely identifying the direct sound arrival time at each receiver position. This information serves multiple purposes: verifying the source-receiver distance, calculating the speed of sound for temperature correction, and providing the reference time point for early reflection analysis. SonaVyx delay finder automatically detects the first arrival in the impulse response, which is the reference point for all time-domain ISO 3382-1 parameters including early decay time, clarity (C80), and definition (D50).
Delay in Room Acoustic Measurement
ISO 3382-1 time-domain parameters require an accurate reference point for the direct sound arrival. The delay finder provides this critical timing reference.
Direct Sound Arrival
- The delay finder identifies the first significant energy arrival in the impulse response
- This marks time zero for EDT, C80, D50, and Ts calculations
- Accurate detection requires adequate SNR in the impulse response
- The detection threshold is typically set at 20 dB below the peak
Distance Verification
- Measured delay multiplied by sound speed gives the source-receiver distance
- Compare against the physically measured distance for consistency check
- Discrepancies indicate either a measurement error or a strong early reflection arriving before the direct sound
- This verification catches setup errors before detailed analysis
Temperature Correction
By measuring both the physical distance and the propagation delay, you can calculate the actual speed of sound and infer the air temperature. This provides a cross-check for the measurement conditions.
Common Mistakes
- Using the impulse peak instead of the first arrival as the timing reference
- Not verifying that the detected arrival corresponds to the direct sound path
- Setting the detection threshold too low, triggering on noise
SonaVyx Workflow
Use the delay finder in the SonaVyx transfer function. Verify with the IR tool visual inspection. Measure RT60 with the RT60 tool. Check levels with the SPL meter. Predict room behavior at AcousPlan. Follow the room analysis workflow.
Standard Reference
ISO 3382-1:
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Last updated: March 19, 2026