Condenser microphones are extremely stable and sensitive transducers when used in their normal operating conditions. When used for long-term noise monitoring, they can be exposed to more extreme environments (e.g. high temperatures, high windspeeds, moisture, etc) which may cause a change in sensitivity, and even damage. The nature of this type of monitoring often precludes a site visit to calibrate the microphone in the normal way, such as using a sound level calibrator or pistonphone mounted directly on the microphone capsule.
We therefore need a method of checking that all is well at the microphone end, so this article describes three methods that can be used.