Mechanical engineering/industrial maintenance and line control

Environmental noise is picked up by the electret microphone* and processed by the instrument. This instrument can be used for quantitative or qualitative analysis of environmental noise in factories, workplaces etc.

* An electret microphone is a microphone with a component called an electret, which can be likened to a capacitor. The latter has the particularity of being permanently polarised at the time of manufacture.
Permanent in theory, because in practice, the polarisation decreases over time, which causes a slow but progressive decrease in the microphone's sensitivity.