Dr. Singh owned two measurement microphones: a Behringer ECM8000 and a UMIK-1. Each had its own calibration file — a list of frequency/correction pairs that compensated for the microphone's deviation from perfectly flat response. The ECM8000's file corrected for a 3 dB rise above 10 kHz. The UMIK-1's file corrected for a 5 dB dip at 8 kHz.

On Tuesday, Dr. Singh measured a concert hall with the ECM8000 but loaded the UMIK-1's calibration file. The measurement software dutifully applied the UMIK-1's corrections to the ECM8000's signal. This meant adding 5 dB at 8 kHz (to compensate for the UMIK-1's dip that didn't exist on the ECM8000) while not correcting the ECM8000's actual 3 dB rise above 10 kHz. The combined error above 8 kHz was approximately 8 dB.

The resulting measurement showed the concert hall's high-frequency reverberant field was 8 dB too bright. Dr. Singh recommended installing high-frequency absorptive treatment at a cost of forty thousand dollars. The treatment was installed. Dr. Singh returned to verify the results, this time with the correct calibration file. The room was now 8 dB too dead above 8 kHz.

The client asked how much it would cost to remove the treatment. Dr. Singh developed a careful system of labeling calibration files after this incident. The labels said 'ECM8000 — THIS ONE' and 'UMIK-1 — NOT THIS ONE.'

The Moral: The wrong calibration file is worse than no calibration file. SonaVyx's mic calibration system clearly displays the active correction curve so you can visually verify it matches your microphone — because a correction for the wrong device is just an error with documentation.