An acoustic calibrator is as important as the noise meter that it accompanies. Careful verification of the sensitivity of the the noise meter and particularly the microphone capsule ensures that the meter is reading correctly before any measurements are undertaken. Although it is considered to be good practice to calibrate a noise meter before making a measurement many protocols specifically mandate that the instrument is calibrated by an independent device before taking serious readings. The use of personal dosimeters for workplace personal noise exposure measurements is one such case where the regulatory body (OSHA, etc.) requires that the dosimeter is checked before (and preferably afterwards too) to ensure it has not drifted during the day.

There are two grades of accuracy specified in the standards for acoustic calibrators classified by their careful adherence to the Class 1 or Class 2 performance standards. A Type 1, or precision, sound level meter should be calibrated by a Class 1 calibrator while a noise dosimeter or a general purpose type 2 sound level meter may be calibrated by a Class 2 calibrator. Tolerances are narrower for the Class 1 devices to ensure the utmost confidence in the measurements. CEL-120/1 or CEL-120/2 calibrators are available for use with relevant sound level meters. The CEL-120/1 Class 1 calibrator has the added advantage of being a dual level, single frequency device for added flexibility.