Calibration

Calibration in acoustic measurement is the process of adjusting a sound level meter or microphone system to ensure that its readings accurately correspond to known sound pressure levels. A pistonphone or acoustic calibrator generates a known level (typically 94 dB or 114 dB at 1 kHz) that is applied to the microphone before and after measurements. IEC 61672-1 and IEC 61672-3 specify calibration requirements for sound level meters, including periodic laboratory calibration (typically annually) and field checks before each measurement session. Calibration is essential for absolute level measurements (SPL, background noise levels) but less critical for relative measurements (reverberation time, clarity) where only the decay shape matters. The calibration correction should not drift by more than 0.5 dB during a measurement session. Maintaining traceable calibration records is required for measurements submitted as evidence of compliance with building regulations.