Microphone Cartridges

4940 1/2-Inch Free Field Microphone

4940 1/2-Inch Free Field Microphone

Prepolarized Free-field ½-inch Microphone Type 4940 offers significant benefits when used with portable instruments. It is particularly suitable for both outdoor and industrial environment measurements. It is also suitable for IEC 60651 Type 1 measurements and frequency analysis measurements.


  • Sound level meters
  • Noise measurements according to IEC and ANSI standards
  • Transport noise measurements


  • Wide dynamic range from 14.6 dB(A) – 146 dB (3% distortion limit)
  • Low ambient temperature coefficient
  • IEC 60651 Type 1 approved with Modular Precision Sound Level Meter Type 2231


The microphone is capable of withstanding the IEC 68 232 1 metre drop test.


The sensitivity can be calibrated at 250 Hz using Pistonphone Type 4228 with ½-inch Adaptor DP 0776. The actuator response can be measured using Actuator UA 0033. The free-field response can be obtained by adding the type-specific, free-field corrections to the actuator response.


Capacitance: 14 pF
Diameter: ½
Dynamic range: 14.6 – 146 dB
Frequency range: 6.3 – 20000 Hz
Inherent noise: 14.6 dB A
Lower limiting frequency -3dB: 4 Hz
Optimised: Free field
Polarization: Prepolarized
Polarization voltages: V
Pressure coefficient: -0.01 dB/kPa
Sensitivity: 50 mV/Pa
Temperature coefficient: -0.001 db/ºC
Temperature range: -30 – 150 C
Venting: Rear
Weight: gram
Sound field: Free-field
Microphone type: Free field