Calibration Q&A

Below you will find some commonly asked questions relating to the calibration of sound level meters and noise measurement equipment.

If you would like more information, please contact us and we will be pleased to help.


Why is calibration of my noise measurement equipment important?

Noise measurement instruments are designed to measure very small changes in pressure and convert these into the information that we are familiar with.

They must meet detailed specifications and performance criteria and any damage to the microphone or measurement chain can affect the accuracy of any measurements that you make.

Regular servicing and calibration can help to identify and resolve any issues and can maintain the level of performance that your equipment had when it was new. Think of this as an MOT for your noise instruments.

Key benefits of a Cirrus service and calibration include:

  • Verification and assurance that the equipment is still accurate
  • A full check of all of the instrument functions with any necessary adjustments made
  • Fixed price service and calibration so you know what the cost will be
  • A full service of all of the parts with minor repairs included
  • A Certificate of Calibration for use in reports and traceability
  • Collection service available

It is also worth considering that if you are working within quality systems such as ISO 9001 and ISO 14001, these will require you to manage and maintain systematic, documented evidence of calibration.

Don't forget that when you have your equipment serviced and calibrated by Cirrus, we'll extend your warranty for a further 12 months, free of charge. (T&C's apply).


I am using an acoustic calibrator each time I make a measurement. Do I still need to have my equipment serviced and calibrated?

Your acoustic calibrator calibrates the sound level meter at one frequency and one level.

This does not check the other frequencies and levels that your equipment will deal with during a measurement and does not check the performance against other types of noise, e.g. impulse noise.

You should always check your equipment each time it is used to check that the overall calibration is still accurate but this does not replace regular servicing and calibration of the equipment.

When you have your equipment serviced and calibrated by Cirrus, we will check all of the functions and capabilities of the instrument against the original specifications and ensure that it continues to meet them.

To keep your measurements accurate you should always continue to calibrate before and after each measurement as well as having your instruments serviced and calibrated by Cirrus at regular intervals.

Our customer services department will be pleased to discuss any questions you have and to arrange for the service and calibration of your equipment.


What should you check before you send your instrument for calibration?

1. Are you sending your instrument to the original manufacturer?

If not, and you are using an independent test laboratory, do they have all of the test information from the manufacturer?

This includes freefield-to-pressure corrections for the microphone, calibration procedures for the specific instrument, how to make adjustments or corrections if these are required, any software required to communicate with and test the instrument.

2. Against what standards will your instrument be tested?

The standards to which the instrument was designed may specify the minimum set of tests that should be carried out. The Certificate of Calibration should state what tests have been carried out along with any standards to which these relate, ie IEC 61672-2002.

3. Will the calibration be sub-contracted to a third party?

If so, make sure that the third party can provide all of the above information.

4. Ensure that you provide paperwork with your instrument

Please make sure that your contact details and any comments are clearly stated.


What do I need to send back with my noise measurement equipment?

We get a large number of parcels and packages from all over the world arriving at Cirrus, some of which are sent without any information or instructions.

Before you send anything back to Cirrus, it's always a good idea to let us know that it is coming. That way we can let you know if anything happens on its way to us.

We would also recommend that you put our address clearly on the outside of the box.

Please also don't forget to include your contact details and any other important information such as a purchase order number or your dBAdvantage Card number.

To help you, we've produced an address label that you can download, print and stick to the box. You can download this label from our website here.


What to check after calibration

When you get your noise equipment back after calibration, check that the work has been done correctly. It is vital that the calibration work has been done in accordance with the standards to which the instrument was designed.

What this means is that it is not sufficient to just check the instrument using an Acoustic Calibrator. Follow this check list to make sure that the instrument has been calibrated correctly and that you have the information you need for your records.

1. Has the microphone capsule been checked for its sensitivity and frequency response?

Microphone capsules are very sensitive and fragile. Even if the microphone appears to be undamaged, it may have lost sensitivity or the frequency response may be compromised. Cirrus will check the sensitivity and frequency response of the microphone separately from the Sound Level Meter using an electrostatic calibration system.

2. Is there a calibration chart for the microphone capsule with this information?

Cirrus will provide a calibration chart for Class 1 microphone capsules which states the sensitivity and frequency response. This information is available on request for Class 2 microphones.

3. Is there a certificate of calibration for the Sound Level Meter showing the serial number and date of calibration?

4. Does the certificate state against which standards the instrument has been checked?

The Certificate of Calibration should state the standards against which the instrument has been tested, ie IEC 61672-2002, IEC 60942:2003, BS7580 Part 1 etc

5. Does the instrument have a calibration sticker showing the correct date and has the internal calibration due date been adjusted?

If the instrument is not calibrated by Cirrus, the internal calibration due date will not be changed and this will appear in any reports that you print.

More Information

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Contact Us

If you have any questions or if you would like any more information, please contact us and we will be pleased to help.

Please call us on
+44 1723 891655.

You can also contact us via our contact form.

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