G.R.A.S. 42AB Sound Calibrator, Class 1

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

Typical applications and use

  • Microphone calibration
  • Microphone comparisons


The G.R.A.S. 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 G.R.A.S. 42AB is supplied with a leather protection case and an individual calibration certificate.

Frequency Hz 1000 (± 0.2 %)
Sound pressure level dB 114 (± 0.2 dB)
ANSI standard S1.40
IEC standard 60942
Temperature range, operation °C / °F -10 to 50 / 14 to 122
Battery type 9V 6LR61
Weight g / oz 220 / 7.76
G.R.A.S. Sound & Vibration reserves the right to change specifications and accessories without notice.


G.R.A.S. RA0297 Adapter (factory mounted) for calibrating 1/2" microphones. Remove this for calibrating 1" microphones.
G.R.A.S. RA0049 Adapter for 1/4" microphones
G.R.A.S. RA0069 Adapter for 1/8"" microphones
G.R.A.S. EL0003 9 V alkaline battery
G.R.A.S. Sound & Vibration reserves the right to change specifications and accessories without notice.