G.R.A.S. 40AG 1/2" Ext. Polarized Pressure Microphone

Freq range: 3.15 Hz to 20 kHz
Dyn range: 20 dBA to 164 dB
Sensitivity: 12.5 mV/Pa
  • 40AG 1/2


The 40AG is an IEC 61094 WS2P ½" externally polarized pressure microphone with rear-venting. Read about the prepolarized equivalent [40AO]

It is a high-precision condenser microphone made according to IEC 61094-4 requirements and is ideal for coupler measurements in both laboratory and production environments. It is extremely robust and reliable and can measure sound pressure levels up to 160 dB within 3.15 Hz to 20 kHz.

40AG 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 broad working range and reliability has made 40AG the preferred externally polarized microphone for coupler and ear simulator setups and is the natural supplement to or replacement of existing solutions. The 40AG is especially suited for audiometer calibration when using a sound level meter / analyzer with a 200 V polarization feature.

It is used for production line testing in coupler setups for test of hearing aids, earphones, headphones, and headsets.

The KEMAR Manikin can also be configured with 40AG for wide-band binaural sound quality recordings.

40AG can be used in

  • RA0039 Ear Simulator according to IEC 60318-1
  • RA0038 ½" 2cc Coupler according to IEC 60318-5
  • KEMAR Manikin (Sound Quality recording)

40AG is included in

  • 46AG ½" Pressure Set
  • RA0045 Externally Polarized Ear Simulator according to IEC 60318-4
  • RA0039 Ear Simulator according to IEC 60318-1
  • 43AA Ear Simulator Kit according to IEC 60318-1 & -2
  • 43AB ½" 2cc Coupler Kit according to IEC 60318-5
  • 43AC Ear Simulator Kit according to IEC 60318-4
  • 43AD Ear Simulator Kit according to ITU-T Rec. P57 Type 1
  • 43AE Ear Simulator Kit according to ITU-T Rec. P57 Type 3.2

 Other coupler systems can be configured with 40AG and a G.R.A.S. LEMO preamplifier on request.


The 40AG requires a standardized ½" or ¼" LEMO preamplifier and an input module that supports this technology with a 7-pin LEMO connector.

System verification

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

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


When leaving the factory, all G.R.A.S. microphones have been calibrated in a controlled laboratory environment using traceable calibration equipment. Depending on the use, measurement environment and internal quality control programs we recommend that the microphone is recalibrated at least once a year.

We offer two kinds of calibration as an optional after-sales service: G.R.A.S. Traceable Calibration and G.R.A.S. Accredited Calibration.

G.R.A.S. Traceable Calibration is a traceable calibration performed by trained personnel under controlled conditions according to established procedures and standards. This is identical to the rigorous calibration that all G.R.A.S. microphones are subjected to as an integral part of our quality assurance.

G.R.A.S. Accredited Calibration is performed by the G.R.A.S. Accredited Calibration Laboratory that has been accredited in accordance with ISO 17025 by DANAK, the Danish Accreditation Fund.

If you want a new microphone set delivered with an accredited calibration in stead of the default factory calibration, specify this when ordering.

Learn more at gras/calib.

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.

Frequency range (±1 dB) Hz 5 to 12.5 k
Frequency range (±2 dB) Hz 3.15 to 20 k
Dynamic range lower limit (microphone thermal noise) dB(A) 20
Dynamic range lower limit with G.R.A.S. preamplifier dB(A) 25
Dynamic range upper limit dB 164
Dynamic range upper limit with G.R.A.S. preamplifier @ +28 V / ±14 V power supply dB 153
Dynamic range upper limit with G.R.A.S. preamplifier @ +120 V / ±60 V power supply dB 164
Open-circuit sensitivity @ 250 Hz (±1 dB) mV/Pa 12.5
Open-circuit sensitivity @ 250 Hz (±1 dB) dB re 1V/Pa -38
Resonance frequency kHz 32
Microphone cartridge capacitance, typ. pF 20
Microphone venting Rear
IEC 61094-4 Compliance WS2P
Temperature range, operation °C / °F -40 to 150 / -40 to 302
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 -0.011
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 66
CE/RoHS compliant/WEEE registered Yes / Yes, Yes
Weight g / oz 7 / 0.247
G.R.A.S. Sound & Vibration reserves the right to change specifications without notice.

Typical frequency response.

Free-field corrections for different angles of incidence

Optional items

G.R.A.S. AF0008

Adapter for ¼” preamplifier and ½” microphone

G.R.A.S. GR0010

Adapter for ¼” preamplifier and ½” microphone

G.R.A.S. RA0001

Right-angled (90°) adapter for ½” microphone and ¼” preamplifier

G.R.A.S. RA0003

Adapter for ¼” preamplifier and ½” microphone

G.R.A.S. RA0016

20 dB Attenuator for externally polarized ½” microphones

G.R.A.S. CA0001

Traceable Calibration of Microphone

G.R.A.S. CA2001

Accredited Calibration of Microphone

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