G.R.A.S. 40AR 1/2" Ext. Polarized Random Incidence Microphone

Freq range: 3.15 Hz to 12.5 kHz
Dyn range: 14 dB(A) to 149 dB
Sensitivity: 50 mV/Pa


The 40AR is an IEC 61094 WS2P/D ½" externally polarized random-incidence microphone with rear-venting. Read about the prepolarized equivalent [40AQ]

The 40AR is a high-precision condenser microphone made according to IEC 61094-4 requirements. It also fulfills the requirements of ANSI S1.4.

This extremely robust and reliable microphone is ideal for random, diffuse, and reverberant sound fields. For a random-incidence microphone, it has a very wide frequency response ranging from3.15 Hz to 16 kHz.

40AR 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 40AR is optimized to measure sound levels correctly in random (diffuse) sound fields e.g. caused by multiple sound sources or hard reverberant surfaces. Random incidence microphones are used e.g. inside vehicles.

The 40AR is included in the G.R.A.S. 46AR 1/2" LEMO Random Incidence Standard Microphone Set.


The 40AR requires a standardized 1/2" or 1/4" 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 42AB

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 12.5 to 8 k
Frequency range (±2 dB) Hz 3.15 to 12.5 k
Dynamic range lower limit (microphone thermal noise) dB(A) 15
Dynamic range lower limit with G.R.A.S. preamplifier dB(A) 19
Dynamic range upper limit dB 149
Dynamic range upper limit with G.R.A.S. preamplifier @ +28 V / ±14 V power supply dB 142
Dynamic range upper limit with G.R.A.S. preamplifier @ +120 V / ±60 V power supply dB 149
Open-circuit sensitivity @ 250 Hz (±1 dB) mV/Pa 50
Open-circuit sensitivity @ 250 Hz (±1 dB) dB re 1V/Pa -26
Resonance frequency kHz 14
Microphone cartridge capacitance, typ. pF 17.5
Microphone venting Rear
IEC 61094-4 Compliance WS2P/D
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 -0.014
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 62
CE/RoHS compliant/WEEE registered Yes / Yes/ Yes
Weight g / oz 6.5 / 0.229

Typical frequency response. Upper curve shows response in a diffuse sound field (random incidence), lower curve shows pressure 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