G.R.A.S. 40HL 1/2'' LEMO Low-noise Microphone System

Freq range: 10 Hz to 16 kHz
Dyn range: 6.5 dB(A) to 110 dB
Sensitivity: 850 mV/Pa

Typical applications and use

  • Measurements at very low sound pressurelevels
  • Measurements on hard-disk drives, computerproducts, anechoic rooms, quiet rooms, etc
  • Sound-power measurements at low levels


The 40HL comprises a special high-sensitive 1/2" free-field measurement microphone and an integrated 1/2" low-noise preamplifier. In combination, they connect to most high-quality input modules with LEMO 1B connector.


The preamplifier, a true 1/2" low-noise amplifIer with LEMO 1B connector, has a built-in compensation filter for free-field microphones.


The 1/2" microphone is an externally-polarized free field 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.

Operating Type 40HL

For holding the microphone, you can order tripods and for level calibration of you need a pistonphone and Calibration Adapter attenuating the pistonphone signal to 94 dB re. 20 µPa. See the tab Ordering info.

Frequency range (±1 dB) Hz 12.5 to 10k
Frequency range (±2 dB) Hz 10 to 16 k
Frequency range (±3 dB) Hz 6 to 20k
Dynamic range lower limit (microphone thermal noise) dB(A) 6.5
Dynamic range upper limit dB 110
Set sensitivity @ 250 Hz (±2 dB) mV/Pa 850
Polarization voltage V 200 V / Traditional
Microphone venting Rear
IEC 61094-4 Compliance WS2F
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
Temperature coefficient @250 Hz dB/°C / dB/°F -0,007 / -0,004
Static pressure coefficient @250 Hz dB/kPa -0.01
Humidity range non condensing % RH 0 to 95
Humidity coefficient @250 Hz dB/% RH 0,001
Influence of axial vibration @1 m/s² dB re 20 µPa 63
Connector type 7-pin LEMO (FGG.1B.307)
CE/RoHS compliant/WEEE registered Yes / Yes / Yes

Typical frequency response

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

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


Optional items

G.R.A.S. AA0008

3 m LEMO-to-LEMO cable

G.R.A.S. AA0009

10 m LEMO-to-LEMO cable

G.R.A.S. AA0020-CL

Customized length LEMO 7-pin - LEMO 7-pin Cable

G.R.A.S. 12AD

1-Channel Power Module

G.R.A.S. 12AR

2-Channel Power Module

G.R.A.S. 12AA

2-Channel LEMO Power Module with gain, filters and Syscheck generator

G.R.A.S. 12AK

1-Channel Power Module with gain, filters and SysCheck generator

G.R.A.S. 12AQ

2-Channel Universal Power Module with signal conditioning and PC interface

G.R.A.S. AL0006


G.R.A.S. RA0093

Adjustable, high quality, stainless steel tripod adapter

G.R.A.S. AM0069

Windscreen for 1/2" Microphones

G.R.A.S. 42AP

Intelligent Pistonphone, Class 0

G.R.A.S. 42AA

Pistonphone, Class 1

G.R.A.S. RA0090

94 dB Pistonphone Coupler

The cables also function as connection cables (to connect 40HL to a power module).

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