G.R.A.S. 40HH 1/2'' Lownoise Microphone System

Freq range: 10 Hz to 16 kHz
Dyn range: 6.5 dB(A) to 113 dB
Sensitivity: 800 mV/Pa

Typical applications and use

  • Very Low Sound pressure measurements
  • Low noise product measurements
  • Sound power measurements at low sound pressure levels
  • Measurements on hard-disk drives, computerproducts, quiet rooms etc.

The 40HH comprises:

The preamplifier and microphone are an individually matched combination. To complete the system, a special single or 10-channel power module is required and is available, i.e. G.R.A.S. 12HF for single-channel measurements or G.R.A.S. 12HM for multi-channel measurements.

The chosen power module provides all necessary voltages for powering the preamplifier(s) as well as polarizing the microphone(s).


The G.R.A.S. 26HH Preamplifier has a built-in overload indicator (which is repeated on the chosen power supply) and a frequency correction facility for both pressure-microphone operation as well as free field microphone operation.


The G.R.A.S. 40AH Microphone is an externally polarized microphone with a specially reduced inherent noise floor in order to achieve a high dynamic range and wide frequency range. Its diaphragm is specially tuned to yield high sensitivity coupled with low internal-noise generation.

Frequency Response and Noise Floor

The chosen power supply has a two-position switch for selecting which microphone operation to use, i.e.pressure or free-field. A typical free-field response for an angle of incidence of 0° is shown in the data sheet when G.R.A.S. 40HH is switched to free-field operation. Also shown is a complete low-noise measuring system, a typical noise floor in 1/3-octave bands for both the linear and A-weighted cases.

Frequency range (±1 dB) Hz 12.5 to 10k
Frequency range (±2 dB) Hz 10 to 16k
Frequency range (±3 dB) Hz 6 to 20k
Dynamic range lower limit (microphone thermal noise) dB(A) 6.5
Dynamic range upper limit dB 113
Set sensitivity @ 250 Hz (±2 dB) mV/Pa 800
Polarization voltage V 200 V / Traditional
Microphone venting Rear
Output impedance Ω 47
Temperature range, operation °C / °F –20 to 60 / -4 to 140
Temperature range, storage °C / °F -40 to 85 / -40 to 185
CE/RoHS compliant/WEEE registered Yes/Yes/Yes

Typical frequency response

Typical noise floor shown in 1/3-octave bands - linear and A-weighted cases


G.R.A.S. 40AH

High sensitive 1/2" microphone

G.R.A.S. 26HH

Lownoise 1/2" preamplifier

Optional items

G.R.A.S. 12HF

1-Channel Power Module for Lownoise Systems

G.R.A.S. 12HM

10-Channel Power Module for Lownoise Systems

G.R.A.S. AM0363

Windscreen for 1" Microphones

G.R.A.S. 42AA

Pistonphone, Class 1

G.R.A.S. RA0090

Pistonphone Coupler

G.R.A.S. AL0006


G.R.A.S. RA0093

Adjustable, high quality, stainless steel tripod adapter

G.R.A.S. RA0095

Dehumidifier for 1” microphones

G.R.A.S. AA0046

3 m LEMO 7-pin - LEMO 7-pin Cable for Low-noise measuring system

G.R.A.S. AA0047

10 m LEMO 7-pin - LEMO 7-pin Cable for Low-noise measuring system

G.R.A.S. AA0053-CL

Customized length LEMO 7-pin - LEMO 7-pin Cable for Low-noise measuring system