GRAS 42AB Sound Calibrator, Class 1

Sound pressure level: 114 dB
Frequency: 1 kHz
ANSI: S1.40
IEC: 60942


As of July 2017, the 42AB Sound Calibrator is replaced with the 42AG Multifunction Sound Calibrator, and the 42AB will therefore no longer be available for normal purchase.

However, if you have specific needs that call for a 42AB - for example for reasons of standardization or as supplement to one or more 42ABs already in your possession -  42AB will be available on request. In this case you should contact GRAS when ordering. We still provide service for 42AB.

Typical applications and use

  • Microphone calibration
  • Microphone comparisons


The GRAS 42AB works at the reference frequency (1 kHz) of the internationally standardized weighting filters A, B, C, and D. This means that it can be used directly for calibrating sound level meters and other similar equipment with these weighting filters activated without having to make corrections.

The calibration level is 114 dB (re. 20 μPa) which corresponds to 10 Pa. This is enough to ensure immunity to background noise without overloading the equipment.

The 42AB consists of a sound source, a reference microphone, and an electronic control circuit. The special reference microphone is extremely stable and independent of variations in barometric pressure, temperature, and humidity. The reference microphone and control circuit together maintain a constant sound pressure level inside the calibration chamber and automatically adjust for changes in load volume, temperature, humidity, and barometric pressure.

Additionally, the calibrator will automatically switch off when the microphone under test is removed from the calibration chamber.

The output level of the 42AB, viz. 114 dB (re.20 μPa) at 1 kHz, meets the requirements of IEC Standard 60942 (2003-01) Class 1 and is therefore in accordance with international standards. It complies with ANSI S1.40 (1997).

The GRAS 42AB is supplied with a leather protection case and an individual calibration certificate.


1000 (± 0.2 %)
Sound pressure level
114 (± 0.2 dB)
ANSI standard
IEC standard
Temperature range, operation
°C / °F
-10 to 50 / 14 to 122
Battery type
9V 6LR61
g / oz
220 / 7.76

Ordering info


GRAS RA0297 Adapter (factory mounted) for calibrating 1/2" microphones. Remove this for calibrating 1" microphones.
GRAS RA0049 Adapter for 1/4" microphones
GRAS RA0069 Adapter for 1/8"" microphones
GRAS EL0003 9 V alkaline battery

GRAS Sound & Vibration reserves the right to change specifications and accessories without notice.

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