G.R.A.S. 40HL 1/2'' LEMO Lownoise 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" lownoise 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.

Frequency Response and Noise Floor

A typical free-field response of G.R.A.S. 40HL at 0° is shown in the data sheet where also the typical noise floor in 1/3-octavebands for both linear and A-weighted cases is shown.

Operating Type 40HL

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

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


High sensitive 1/2" microphone

Lownoise 1/2" preamplifier with built-in TEDS and LEMO connector

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

Pistonphone Coupler

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