08. Acoustic Calibration Services

The G.R.A.S. Accredited Calibration Laboratory is accredited by DANAK, the Danish Accreditation Fund. This accreditation is a quality label that proves that our calibration laboratory complies with the ISO 17025 standard for laboratories.



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If your quality assurance programs demand it, or if you for other reasons need the enhanced confidence that comes with an internationally recognized quality label, a G.R.A.S. Accredited Calibration is the right choice.


Laboratory Reference Microphones - G.R.A.S. 40EU & 40 AU 

Available in both 1” (G.R.A.S. 40EU) and 1/2” (G.R.A.S. 40AU) versions, G.R.A.S. laboratory reference microphones are designed and manufactured to the IEC 61094-2 reference standard and recognized by some of the world’s most prominent international metrology laboratories for their quality and performance. 

Both types are typically used to perform pressure calibration functions in acoustic couplers, such as reciprocity or traditional pistonphone calibration.


Patented Intelligent Pistonphone Calibrator - G.R.A.S. 42AP 

For the optimum performance of measurement microphones, G.R.A.S. recommends use of high-precision pistonphone calibrators. These portable handheld calibrators generate a 250 Hz tone, at which typical microphone response is flat, providing greater likelihood of accurate calibration results.

Traditional pistonphones require use of a separate barometer for applying static pressure corrections. The new patented G.R.A.S. 42AP Intelligent Pistonphone Calibrator has a built-in precision barometer, allowing for automatic in-situ correction of the static pressure and readout of actual corrected pressure level via its display or RS-232 interface. The G.R.A.S. 42AP pistonphone will also readout the exact static air pressure at its position and temperature (°C or °F), and corrects for possible A-weighting. It is IEC 60942 (2003) LS compliant. The unit is delivered with calibrated couplers and adapters for 1’’, 1/2’’, 1/4’’ and 1/8‘’ microphones and an interface cable.


Low- frequenct calibrator to 0.01 Hz - G.R.A.S. 42AE

Designed for use with both front and rear-vented G.R.A.S. measurement microphones, the two-port configuration of the G.R.A.S. 42AE permits simultaneous monitoring of actual sound pressure in the coupler by a reference microphone with the microphone under test. Sound pressure can alternatively be monitored using the voltage output proportional to the pressure in the coupler. The built-in, DC-coupled power amplifier enables the calibrator to be used for swept-sine, broadband and step function investigations. Various types of adapters, for calibration of 1/8’’ to 1’’ microphones and preamplifiers are included.



Microphone Calibration System - G.R.A.S. 90CA

The G.R.A.S. 90CA Microphone Calibration System offers level and frequency response calibrations of IEC 61094 standardized 1’’, 1/2’’ and 1/4’’ measurement microphones, preamplifiers and microphone sets. Designed to reduce the risk of operator error, the 90CA comes with ready-to-use hardware and software, allowing for automatic calibrations in four easy steps, including:

Microphone Registration

The user can enter test condition data and microphone parameters. For G.R.A.S. microphones, a built-in database of calibration parameters is pre-programmed and can be expanded to include other manufacturers’ models.

Level Calibration

Using the supplied pistonphone and insert-voltage preamplifier, open-circuit sensitivity is determined at 250 Hz, 114 dB.


Frequency Calibration

An electrostatic actuator determines microphone frequency response, with customizable range and steps.


Calibration Certificate

Complete calibration data is saved as a text file. The system auto-generates a calibration certificate as a PDF file, which is fully customizable and printable with logo, etc.


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