Field Story

Failing BB93: The Auditorium That Could Not Graduate

A new school auditorium failed its BB93 acoustic assessment with RT60 of 1.9 seconds at 500 Hz against the 1.0-second requirement. The building could not receive its occupancy certificate. Impulse response measurements across 6 receiver positions confirmed the issue. Installing Class A absorbers on 35% of the rear wall and ceiling clouds above the seating brought RT60 to 0.95 seconds, passing the standard.

School Auditorium

Polarity Checker per ISO 3382-2

TL;DR

Polarity verification supports ISO 3382-2 measurements in ordinary rooms by ensuring consistent impulse response convention across all source-receiver combinations. When multiple measurement positions are compared, an inadvertent polarity inversion at one position can create apparent spatial variation that does not actually exist. SonaVyx polarity checker validates your measurement chain at the start of each session and can be re-run after any cable or equipment changes. This simple pre-check prevents subtle data quality issues that might not be obvious until the analysis stage.

Polarity Consistency in Multi-Position Measurements

ISO 3382-2 requires measurements at multiple source and receiver positions. Consistent polarity across all positions is essential for comparable results.

Why Polarity Matters

  • RT60 magnitude is not affected by polarity inversion
  • However, time-domain analysis (ITDG, early reflection patterns) depends on correct polarity
  • Averaging impulse responses across positions requires consistent polarity
  • Polarity errors create apparent discrepancies between measurement positions

Verification Protocol

  1. Check polarity at the start of the measurement session
  2. Re-check after any cable, microphone, or interface changes
  3. Use the same polarity reference method (positive pressure test) each time
  4. Document the polarity status in the measurement log

Common Equipment Issues

In ordinary room measurements, portable equipment setups are common. Quick connections and cable swaps increase the risk of polarity errors. A systematic polarity check protocol prevents these issues.

Common Mistakes

  • Assuming polarity is correct without verification
  • Not re-checking after equipment changes during a session
  • Comparing measurements from sessions with different polarity conventions

SonaVyx Workflow

Verify with the SonaVyx polarity checker. Measure RT60 with the RT60 tool. Capture IRs with the IR tool. Check levels with the SPL meter. Predict room behavior at AcousPlan. Follow the room analysis workflow.

Standard Reference

ISO 3382-2:

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Last updated: March 19, 2026