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

Freq range: 3.15 Hz to 20 kHz
Dyn range: 20 dB(A) to 164 dB
Sensitivity: 12.5 mV/Pa
  • 40AU 1/2

Introduction

The 40AU is an IEC 61094 LS2aP ½" externally polarized reference microphone that is rear-vented.

It is a ½" laboratory-standard pressure microphone that is ideal for precision sound pressure measurements. It has a front cavity as specified in IEC 61094-2 and is supplied with a protective dust cap.

40AU 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 40AU can be used for precision sound pressure measurements, calibrations at high frequencies, laboratory reference measurements, and measurements in couplers and ear simulators.

The 40AU can be used in couplers, ear simulators, enclosures, and at boundaries.

Compatibility

The 40AU 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 42AB

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

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.

Service

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.

Calibration 

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.

TYPE (Microphone features) P
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 (±2 dB) mV/Pa 12.5
Open-circuit sensitivity @ 250 Hz (±2 dB) dB re 1V/Pa -38
Resonance frequency kHz 32
Microphone cartridge capacitance, typ. pF 20
Microphone venting Rear
IEC 61094-4 Compliance LS2aP
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 -0.007
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

Typical frequency response

Free-field corrections for different angles of incidence

AF0008

Adapter for ¼” preamplifier and ½” microphone

GR0010

Adapter for ¼” preamplifier and ½” microphone

RA0001

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

RA0003

Adapter for ¼” preamplifier and ½” microphone

RA0016

20 dB Attenuator for externally polarized ½” microphones