Calibration of sound level meters

Purpose

The national laboratories are responsible for maintaining the national reference standards for each measurement quantity and spreading metrological competence and traceability to industry and society at large. The national reference standards are the highest level of traceability in Sweden.

A calibration performed at a national laboratory fulfils all typical traceability and accreditation requirements that commonly exist in industry and society at large. 

Method

The characteristics of sound level meters are specified in the international standard IEC 61672, or for older instruments IEC 60651 and IEC 60804. Measurement procedures and tolerances to verify that the characteristics of the sound level meter are correct are also stated in these standards. Examples of characteristics which are tested: frequency response of microphone and filter, the different time weightings (Fast, Slow etc.), level linearity, overrange indication etc.

Sound level meters are divided into different classes of accuracy, where class 1 is normal for precision measurements and class 2 for simpler measurements. Approximate accuracy for a sound level meter of class 1 is 1 dB and 2 dB for class 2. However, the accuracy is dependent on the character of the sound.

Sound level meters have often an octave band analysis feature. Characteristics for this is specified in a separate standard, IEC 61260.

Deliveries

The calibration results are reported in a digital calibration certificate in Swedish or English which states that the calibration was performed at a national laboratory.