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40AO 1/2" Prepolarized Pressure Microphone
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40AO 1/2" Prepolarized Pressure Microphone
The 40AO is an IEC 61094 WS2P ½" prepolarized pressure microphone with rear-venting. Read about the externally polarized equivalent [40AG]. 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 in the range of 3.15 Hz to 20 kHz. 40AO is individually factory-calibrated and delivered with a calibration chart stating its specific open-circuit sensitivity and pressure frequency response.
The broad working range and reliability has made 40AO the preferred prepolarized microphone for coupler and ear simulator setups and is the natural supplement or replacement of existing solutions. The 40AO is especially suited for audiometer calibration when using a sound level meter / analyzer without a 200 V polarization feature.
It is used for production line testing in coupler setups for test of hearing aids, earphones, headphones, and headsets.
Key Specifications
| Polarization/Connection | 0 V / CCP |
| Frequency range (±1 dB) | 5 Hz to 12.5 kHz |
| Frequency range (±2 dB) | 3.15 Hz to 20 kHz |
| Dynamic range lower limit (microphone thermal noise) | 20 dB(A) |
| Dynamic range lower limit with GRAS preamplifier | 25 dB(A) |
| Dynamic range upper limit | 163 dB |
| Dynamic range upper limit with GRAS preamplifier @ +28 V / ±14 V power supply | 153 dB |
| Dynamic range upper limit with GRAS preamplifier @ +120 V / ±60 V power supply | 163 dB |
| Dynamic range upper limit with GRAS preamplifier | 150 dB |
| Open-circuit sensitivity @ 250 Hz (±3 dB) | 12.5 mV/Pa |
| Open-circuit sensitivity @ 250 Hz (±3 dB) | -38 dB re 1V/Pa |
| Resonance frequency | 32 kHz |
| Microphone cartridge capacitance, typ. | 20 pF |
| Microphone venting | Rear |
| Temperature range, operation | -40 to 120 °C / -40 to 248 °F |
| IEC 61094-4 Designation | WS2P |
| Temperature range, storage | -40 to 85 °C / -40 to 185 °F |
| Temperature coefficient @250 Hz | -0.01 dB/°C / -0.006 dB/°F |
| Humidity range non condensing | 0 to 90 % RH |
| Static pressure coefficient @250 Hz | -0.007 dB/kPa |
| Humidity coefficient @250 Hz | -0.001 dB/% RH |
| Influence of axial vibration @1 m/s² | 66 dB re 20 µPa |
| Weight | 6.5 g / 0.229 oz |
Specifications from the official GRAS product sheet. Please refer to the attached datasheet for full details.
