G.R.A.S. 67AX ø400 mm CCP Ground Array Microphone Kit

Freq range: 3.15 Hz to 20 kHz
Dyn range: 22 dB(A) to 150 dB
Sensitivity: 12.5 mV/Pa
  • 67AX ø400 mm CCP Ground Array Mic Kit

Typical applications and use

  • Ground array measurements
  • General noise measurements
  • Ideal for the aerospace industry


The 67AX is a ground array microphone kit designed for the aerospace industry, i.e. for measurement of noise from overhead aircraft.

The microphone set is designed to sit asymmetrically in the mounting to attain a more uniform frequency response for measurements.

The G.R.A.S. 47AX microphone is a IEC 61094 1/2'' CCP Flush-mount Microphone Set with a dynamic range from 22 dB to 150 dB and a frequency range from 3.15 Hz to 20 kHz. Its height of only 8 mm (to the diaphragm) is the ideal match for the design of the 67AX. The built-in preamplifier is a low noise constant current power (CCP) type, with a built-in TEDS circuit for automatic transducer identification.

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) 22
Dynamic range upper limit dB 150
Dynamic range upper limit with G.R.A.S. CCP preamplifier dB 149
Set sensitivity @ 250 Hz (±2 dB) mV/Pa 12.5
Polarization voltage V 0
Microphone venting Rear
Output impedance Ω <50
Temperature range, operation °C / °F -30 to 70 / -22 to 158
Temperature range, storage °C / °F -40 to 85 / -40 to 185
Static pressure coefficient @250 Hz dB/kPa -0.008
Humidity range non condensing % RH 1 to 100
Humidity coefficient @250 Hz dB/% RH < 0.1
Influence of axial vibration @1 m/s² dB re 20 µPa 66
TEDS UTID (IEEE 1451.4) 27 v. 1.0
Connector type BNC
CE/RoHS compliant/WEEE registered Yes/Yes/Yes
Weight g / oz 15 / 0.529

Placement of the microphone in the plate with the windscreen on top. The cutaway of section A to A shows how the microphone fits into the plate.

Included items

G.R.A.S. 47AX-S1 1/2'' CCP Flush-mounted Microphone Set
G.R.A.S. GR1425 Ground plate Ø400 mm
G.R.A.S. AM0375 Windscreen for 67AX
G.R.A.S. AA0069 3 m Microdot Angled - BNC cable

Optional accessories

G.R.A.S. 42AP Intelligent Pistonphone, Class 0
G.R.A.S. RA0216 Pistonphone field-verification adapter
G.R.A.S. RA0221 Pistonphone calibration adapter