Microphone Cartridges

4939 1/4-Inch Free Field Microphone

4939 1/4-Inch Free Field Microphone

Free-field ¼” microphone Type 4939 is specially designed for high-level and high-frequency measurements. By using stainless steel diaphragm and protection grid, the microphone is optimised to withstand rough environments and is capable of working at high temperatures up to 150°C (302°F).


  • High level measurements
  • High frequency measurements
  • Model work


The microphone is capable of withstanding the IEC 68-2-32 1 metre drop test.


The sensitivity can be calibrated at 250 Hz by using Pistonphone Type 4228 with ¼” Adaptor DP 0775. The actuator response can be measured using Actuator UA 0033 with Adaptor DB 0264. The free-field response can be obtained by adding the type-specific, free-field correction to the actuator response.

Capacitance: 6.1 pF
Diameter: 1/4
Dynamic range: 28 – 164 dB
Frequency range: 4 – 100000 Hz
Inherent noise: 28 dB A
Lower limiting frequency -3dB: 3 Hz
Optimised: Free field
Polarization: Ext polarized
Polarization voltages: 200 V
Pressure coefficient: -0.007 dB/kPa
Sensitivity: 4 mV/Pa
Standards: IEC 61094-4 WS3F
Temperature coefficient: 0.003 db/ºC
Temperature range: -40 – 150 C
Venting: Side
Weight: gram
Sound field: Free-field
Input type: Classic
Microphone type: Free field