G.R.A.S. 50GI CCP Intensity Probe

Freq range: Ref. IEC 61043 Class 1
Dyn range: 27 dB(A) to 163
Sensitivity: 12.5 mV/Pa

Typical applications and use

  • Sound intensity measurements
  • Sound source location
  • Sound power measurements
  • IEC 61043 standard measurements
  • Sound source ranking
  • Sound intensity mapping


The probe set includes solid interchangeable spacers for microphone separations from 12 mm to 100 mm so that the probe can cover the frequency range from 50 Hz to 10 kHz.

All components are made specifically for sound intensity applications. Each small 1/4" diameter by 40 mm long microphone preamplifier is housed in a robust stainless steel casing, which enables novel probe designs for reducing disturbances to the soundfield otherwise brought about by the effects of shadows and diffraction, and a symmetry which enables reliable calibrations as described in the proposed standard (ISO/DIS 9614-2) for sound power measurements using sound intensity measurements.

The CCP Intensity Probe G.R.A.S. 50GI comprises 40GK sound Intensity Microphone Pair, two 26CB CCP Microphone Preamplifiers, four solid spacers of various lengths, windscreen, and probe handle.

The Type 50GI is delivered in a carrying case as a ready-to-use kit, complete with all the above accessories.

The microphones are 1/2/ free-field prepolarized microphones with a uniquely-designed pressure equalisation system which ensures extremely well defined phase characteristics.

The microphones and preamplifiers are mounted on a swivel head on the telescopic arm of the handle. To cover the full frequency range from 50 Hz to 10 kHz, the 50GI probe is delivered with four solid spacers for spacing the microphones at 12 mm, 25 mm, 50 mm and 100 mm. These spacers can be easily interchanged without dismantling the probe.

Frequency range (±2 dB) Hz Ref. IEC 61043 Class 1
Dynamic range lower limit (microphone thermal noise) dB(A) 27
Dynamic range upper limit dB 146
Set sensitivity @ 250 Hz (±2 dB) mV/Pa 12.5
Polarization voltage V 0
Microphone venting Rear
Temperature range, operation °C / °F 5 to 40 / 41 to 104
Temperature coefficient @250 Hz dB/°C / dB/°F -0.01
Humidity range non condensing % RH 0 - 100
Humidity coefficient @250 Hz dB/% RH -0.001
Influence of axial vibration @1 m/s² dB re 20 µPa 66
Connector type BNC
CE/RoHS compliant/WEEE registered Yes/Yes/Yes
Weight g / oz 300 / 10.582

Frequency ranges for different microphone spacers

G.R.A.S. Sound & Vibration reserves the right to change specifications and accessories without notice.

Included items

G.R.A.S. 40GK 1/2" Prepolarized Intensity Microphone Kit
G.R.A.S. 26CB Set 1/4" CCP Standard Preamplifier with Microdot connector
G.R.A.S. AA0070 3 m Microdot - BNC cable
G.R.A.S. AI0044 Probe handle
G.R.A.S. AI0001 Windscreen for Intensity Probes

Optional accessories

G.R.A.S. AA0046 Extension cables for Lownoise Measuring Systems Type 40HF/40HH
G.R.A.S. 12AQ 2-Channel Universal Power Module with signal conditioning and PC interface
G.R.A.S. 42AP Intelligent Pistonphone, Class 0
G.R.A.S. 51AB Phase Calibrator according to IEC 61043

G.R.A.S. Sound & Vibration reserves the right to change specifications and accessories without notice.