G.R.A.S. 40BE-FV 1/4" Prepolarized Free-Field Microphone, Front Vented

Freq range: 4 Hz to 80 kHz
Dyn range: 30 dB(A) to 168 dB
Sensitivity: 4 mV/Pa


It is a high-precision condenser microphone made according to IEC 61094-4 requirements. Its dynamic range makes it suitable for high-frequency or high-level measurements, as well as acoustic transient measurements. It is extremely robust and reliable and can measure sound pressure levels up to 168 dB in the range of 4 Hz to 100 kHz.

40BE-FV is individually factory-calibrated and delivered with a calibration chart stating its specific open-circuit sensitivity and pressure frequency response. 

Typical applications and use

The 40BE-FV is ideal for sound measurements at very high frequencies and levels, as well as acoustic transient measurements. It is suitable for general purpose measurements in open acoustic fields. 


The 40BE-FV requires a standardized 1/2" or 1/4" CCP preamplifier and an input module that supports this technology with a BNC, SMB, or Microdot connector.

System verification

For daily verification and check of your measurement setup, we recommend using a calibrator like G.R.A.S. 42AG Sound Level Calibrator. 

For proper sensitivity calibration, we recommend using a pistonphone like G.R.A.S. 42AP Intelligent Pistonphone. 

Quality and warranty

All G.R.A.S. microphones are made of high-quality materials that will ensure life-long stability and robustness. The microphones are all assembled in verified clean-room environments by skilled and dedicated operators with many years of expertise in this field.

The microphone diaphragm, body, and improved protection grid are made of high-grade stainless steel, which makes the microphone resistant to physical damage, as well as corrosion caused by aggressive air or gasses.

This, combined with the reinforced gold-plated microphone terminal which guarantees a highly reliable connection, enables G.R.A.S. to offer 5 years warranty against defective materials and workmanship.


If you accidentally damage the diaphragm on a G.R.A.S. microphone, we can—in most cases—replace it at a very reasonable cost and with a short turn-around time. This not only protects your investment, but also pleases your quality assurance department because you don’t have to worry about new serial numbers, etc.


Before leaving the factory, all G.R.A.S. microphones are calibrated in a controlled laboratory environment using traceable calibration equipment.

Depending on the use, measurement environment, and internal quality control programs, we recommend recalibrating the microphone at least once a year.

Frequency range (±1 dB) Hz 10 to 40 k
Frequency range (±2 dB) Hz 4 to 80 k
Frequency range (±3 dB) Hz 4 to 100 k
Dynamic range lower limit (microphone thermal noise) dB(A) 30
Dynamic range lower limit with G.R.A.S. preamplifier dB(A) 35
Dynamic range upper limit dB 168
Dynamic range upper limit with G.R.A.S. preamplifier @ +28 V / ±14 V power supply dB 164
Dynamic range upper limit with G.R.A.S. preamplifier @ +120 V / ±60 V power supply dB 168
Dynamic range upper limit with G.R.A.S. CCP preamplifier dB 160
Open-circuit sensitivity @ 250 Hz (±3 dB) mV/Pa 4
Open-circuit sensitivity @ 250 Hz (±3 dB) dB re 1V/Pa -48
Resonance frequency kHz 100
Microphone cartridge capacitance, typ. pF 5
Microphone venting Front
IEC 61094-4 Compliance WS3F
Temperature range, operation °C / °F -40 to 120 / -40 to 248
Temperature range, storage °C / °F -40 to 85 / -40 to 185
Temperature coefficient @250 Hz dB/°C / dB/°F -0.01 / -0.006
Static pressure coefficient @250 Hz dB/kPa -0.013
Humidity range non condensing % RH 0 to 100
Humidity coefficient @250 Hz dB/% RH -0.001
Influence of axial vibration @1 m/s² dB re 20 µPa 60
CE/RoHS compliant/WEEE registered Yes / Yes, Yes
Weight g / oz 1.75 / 0.062

Typical frequency response (without protection grid). Upper curve shows free-field response for 0°, lower curve shows pressure response.

G.R.A.S. Sound & Vibration reserves the right to change specifications and accessories without notice.