The calibration of microphones using an electrostatic actuator is a widely applied laboratory method for the determination of frequency response characteristics of measurement microphones. The actuator produces an electrostatic force that simulates a sound pressure acting on the microphone diaphragm.

In comparison with sound-based methods, the actuator method has a great advantage; it provides a simpler means of producing a well-defined calibration pressure over a wide frequency range without the special facilities of an acoustics laboratory.

The actuatorís construction allows for the calibration of surface microphone Types 4948 and 4949, even when the microphone is mounted in Mounting Flange UA-1640.


  • Simple setup
  • Calibrate microphones with or without Mounting Flange UA-1640
  • Functions like other Brüel & Kjær electrostatic actuators


  • Frequency response calibration of Types 4948 and 4949

Pressure-field Corrections

Pressure-field correction (PFC) must be added to the result achieved with UA-1639 in order to establish the pressure-field response, which is shown on the original calibration chart. Performing repetitive measurements, including remounting, is recommended to detect possible random resonances. Any non-repeatable peak or dip in the frequency response is probably caused by such resonances and should be omitted from the test results.