Good measurement practice can reduce the likelihood and severity of measurement errors, and thus reduce the risks defined in Risk Assessment.

For a description of good measurement practice, refer to the NPL guide on Performance Verification of Measurement Systems. Other sources of guidance can also be sought.

Key items relating to the calibration of acoustical systems are covered below:

Treat your Instruments Properly

Instrument accuracy can be adversely affected by:

• Dampness or humidity
• Temperature extremes
• Dirt, dust
• Shocks, impacts or vibration
• Rapid or significant pressure fluctuations

Avoid these factors when transporting or storing equipment. If an instrument is subjected to any of these factors, calibration and checks should be carried out on a more regular basis than that suggested in the UKAS Lab 23 document.

Use a Portable Calibrator

The use of a portable calibrator is recommended to check readings obtained using the whole measurement chain. Using a calibrator at more than one frequency and amplitude will also provide a basic check for the linearity and frequency response of the system.

A portable calibrator should generally be calibrated to a traceability of Level 1, ideally carried out in conjunction with the calibration of the microphones or sound level meters to be used with the calibrator.

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