For many applications it is important to know the frequency response of the measurement microphone. There are a number of methods available for determination of the frequency response of a microphone. Some of the methods are described in IEC standards, namely, 1094-2 and 1094-3. For the special laboratory standard microphones, as described in LS1P and LS2P (IEC 1094-1), it is possible to have a primary calibration at a national calibration laboratory. Most of the other measurement microphones are normally calibrated using the electrostatic actuator calibration method. The actuator response is measured, and the free-field corrections supplied by the microphone manufacturer are added. From most manufacturers no information about the uncertainty on the determination of the actuator response and the free-field corrections has been available. A complete set of uncertainty values for actuator responses and free-field corrections for the new Bruel & Kj(ae ligature)r Falcon Range microphones will be presented and discussed.