G.R.A.S. 47BX 1/4" CCP Flush-mount Microphone Set

Freq range: 4 Hz to 70 kHz
Dyn range: 44 dB(A) to 166 dB
Sensitivity: 1.6 mV/Pa

Typical applications and use

  • Flush mounting in confined spaces
  • Flush mounting in clay models
  • Flush mounting in scale models for wind tunnel tests
  • Ground array measurements
  • General noise measurements


With a height (to the diaphragm) of only 8 mm, 47BX is suitably designed for flush mounting in plates in ground array applications and other applications with size constraints.

The microphone is a prepolarized pressure microphone with a dynamic range from 44 dB to 165 dB and a frequency range from 4 Hz to 70 kHz. The built-in preamplifier is a low noise constant current power (CCP) type, with a built-in TEDS circuit for automatic transducer identification. The set has an integrated 1.5 m cable (G.R.A.S. 47BX-CL with customized length optional) with Microdot connector plus an adapter for BNC cable.

Flush-mounting is ideal where holes can be made in the structure, such as a clay model, to accommodate the front-vented 47BX. A rear-vented version is also available, the 47BX-S1

The 47BX is based on the IEC 61094 standard for measurement microphones.

Frequency range (±1 dB) Hz 10 to 25 k
Frequency range (±2 dB) Hz 4 to 70 k
Dynamic range lower limit (microphone thermal noise) dB(A) 44
Dynamic range upper limit with G.R.A.S. CCP preamplifier dB 166
Set sensitivity @ 250 Hz (±2 dB) mV/Pa 1.6
Polarization voltage V 0
Power supply (Constant Current Power) mA 2 to 10
Microphone venting Front
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 0 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 Microdot 10/32
CE/RoHS compliant/WEEE registered Yes/Yes/Yes
Weight g / oz 7.5 / 0.265

Typical frequency response

All dimensions in mm.

Included items

G.R.A.S. AE0046

Microdot - BNC male adapter


Optional items

G.R.A.S. 12AL

 1-Channel CCP Power Module with A-weighting filter

G.R.A.S. 42AP

Intelligent pistonphone

G.R.A.S. RA0228

Pistonphone Calibration Adapter for 1/4" Flush-mount Microphone Sets

G.R.A.S. RA0302

Removal Tool for 1/2” & 1/4” Flush-mount Microphones

G.R.A.S. RA0502

Mounting Adapter for 1/4” Flush-mount Microphone Set

G.R.A.S. AE0074

BNC male to female adapter

G.R.A.S. AA0035

3 m BNC - BNC Cable

G.R.A.S. AA0037

10 m BNC - BNC Cable

G.R.A.S. AA0039-CL

Customized length BNC - BNC Cable