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TYPE 4964

1/2" INFRASOUND MICROPHONE, PREPOLARIZED

Infrasound microphone specifically designed for high-precision, acoustic measurements with high sensitivity in the frequency range of 0.02 Hz to 20 kHz.

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TYPE 4964

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Infrasound Microphone Cartridge Type 4964 is designed for high-precision, acoustic measurements where an infrasound microphone with high sensitivity is required. Being prepolarized, Type 4964 can be used with both CCLD and classical preamplifiers, and makes the microphone especially well-suited for battery operated equipment and operation in environments with high humidity.

  • General noise measurements
  • Wind turbine measurements
  • Sonic boom measurements
TYPE 4964
Standard IEC 61094
Sound field Free field
Polarization voltage 0V
Sensitivity 50 mV/Pa
Lower limiting frequency 0.02 Hz
Higher limiting frequency 20 kHz
Inherent noise 14.2 dB(A)
Upper limiting of dynamic range 146 dB
Diameter 1/2 inch
Venting Rear
Minimum Temperature -30 °C
Maximum Temperature 150 °C
Minimum Temperature -22 °F
Maximum Temperature 302 °F

INFRASOUND AND FREE-FIELD RESPONSE

At infrasound and frequencies below a few kHz, the pressure and free-field response are the same. At higher frequencies, reflections and diffractions cause pressure to increase in front of a microphone's diaphragm.

Type 4964 has been optimized for free-field, and designed for use with the protection grid in place. Type 4964 is also suited for use in class 1 sound level meters and for all high-precision acoustic measurements where a robust and stable free-field microphone with an upper frequency of 20 kHz is required.

BUILD AND STABILITY

A press-fitted, stainless-steel diaphragm ensures superior longterm stability and mechanical robustness – Type 4964 will withstand the 1 m drop test of IEC 60068–2–32.

INDIVIDUAL CALIBRATION

As all Brüel & Kjær microphones, each Type 4964 is provided with an individual calibration chart including information about the open-circuit sensitivity, the frequency response in a free field as well as the electrostatic actuator response. Using the calibration data and the REq-X feature of LAN-XI, a real-time correction for different measurement situations can increase accuracy.