G.R.A.S. 40EN 1" Ext. Polarized Pressure Microphone

Freq range: 2.6 Hz to 8 kHz
Dyn range: 9.6 dBA to 146 dB
Sensitivity: 50 mV/Pa


The 40EN is an IEC 61094 WS1P 1" externally polarized pressure microphone.

It is a 1" pressure microphone that is ideal for measurements in couplers used for testing earphones. When flush-mounted, it can measure sound pressures at boundaries. It is highly suited as a laboratory-standard microphone.

The 40EN can be vented in three different ways to suit your application requirements.

40EN 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 40EN has a flexible design for venting. It is delivered as front-vented from the factory due to a special O-ring included in the microphone assembly. Using a special G.R.A.S. tool, you can replace this O-ring with a different O-ring (included) that makes the microphone rear-vented. Using both O–rings makes the microphone non-vented.

40EN is included in

  • 43AF 1" 6cc Coupler Kit according to IEC 60318-3


The 40EN requires a standardized ½" 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 (±2 dB) Hz 2.6 to 8 k
Dynamic range lower limit (microphone thermal noise) dB(A) 9.6
Dynamic range lower limit with G.R.A.S. preamplifier dB(A) 14
Dynamic range upper limit dB 146
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 146
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 8
Microphone cartridge capacitance, typ. pF 56
Microphone venting Rear
IEC 61094-4 Compliance WS1P
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 -0.0016
Humidity range non condensing % RH 0 to 100
Humidity coefficient @250 Hz dB/% RH -0.0013
Influence of axial vibration @1 m/s² dB re 20 µPa 67
CE/RoHS compliant/WEEE registered Yes / Yes, Yes
Weight g / oz 32 / 1.129

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

Typical frequency response

Free-field corrections for various angles of incidence

Optional items

G.R.A.S. RA0017

½” Preamplifier to 1” Microphone Adapter

G.R.A.S. RA0073

½” Preamplifier to 1” Microphone Adapter

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.