G.R.A.S. 41AL Environmental Microphone

Freq range:3.15 to 12.5
Dyn range: < 17 dB(A) to > 156 dB
Sensitivity: 50 mV/Pa

Typical applications and use

  • Outdoor-noise measurements
  • Traffic-noise monitoring
  • IEC 60651 Sound Level Meter measurements
  • Environmental surveillance


The G.R.A.S. 41AL Environmental Microphone is a precision microphone unit for outdoor measurements and can withstand continuous rain and operate over wide temperature ranges. They are for short-term outdoor acoustic measurements and noise monitoring covering periods from a few days to several weeks. They are a low-cost alternative to the G.R.A.S. Outdoor Microphone Systems 41AM and 41CN (see separate data sheets) which are for permanent outdoor use, e.g. in airport noise monitoring systems.

'The special ½″ condenser microphone in each 41AL is optimized to comply with IEC 651 Type 1 and ANSI S1.4 1983 Type 1 requirements with the foam windscreen, anti-bird-spikes and rain protection cap fitted; whereas standard microphones such as the G.R.A.S. 40AF are optimized for measurements with only the standard protection grid fitted.

In order for the rain protection cap and foam windscreen to protect the microphone properly, the microphone’s diaphragm must be kept horizontal; i.e., the orientation of the 41AL relative to the sound source cannot be adjusted. To meet the relevant standards, which prescribe both 0º incidence and 90º incidence, we therefore offer versions of both angles of incidence. The 0º-version is for aircraft fly-over noise measurements and other applications where the microphone’s reference direction points upwards. The 90º-version is for measuring community noise, traffic noise, vehicle pass-by noise etc., and other applications where the microphone’s reference direction points horizontally.

As a stand-alone unit, the 41AL fulfils theIEC 651 requirements for a Type 1 Sound Level Meter. This means that its specifications have to be better than the IEC 651 requirements so that when connected to an analyzer or sound level meter, also subject to similar stringent requirements, the measuring system as a whole still fulfils the IEC651 requirements. For example, IEC 651 specifies a frequency response within ±1 dB from 100 Hz to 4 kHz for a Type 1 Sound Level Meter. To allow for additional tolerances in the connected instrumentation, the 41AL is specified to be within ±0.7 dB from 100 Hz to 4 kHz.

A desiccator unit is available if the 41AL is to be placed outdoors for extended periods. The desiccators crews directly onto the base of the 41AL and removes moisture from the air entering the unit.

Frequency range (±1 dB) Hz 12.5 to 80
Frequency range (±2 dB) Hz 3.15 to 12.5
Dynamic range lower limit with G.R.A.S. preamplifier dB(A) < 17
Dynamic range upper limit dB > 156
Set sensitivity @ 250 Hz (±2 dB) mV/Pa 50
Polarization voltage V 200
Power supply, single V 28 to 120 (single) / ± 14 to ± 60 (dual)
Power consumption mA 0.7 at ±14 V / 2.3 at ±60 V
Output impedance Ω 75
Temperature range, operation °C / °F - 40 to 60 / -40 to 15.6
TEDS UTID (IEEE 1451.4 ) 27 v. 1.0
Connector type 3 m 7-pin LEMO
CE/RoHS compliant/WEEE registered Yes / Yes / Yes
Weight g / oz 200 / 7.055
Frequency response according to IEC 651 Type 1 and ANSI S1.4-1983 Type 1

Included items

G.R.A.S. AM0145 Complete windscreen
G.R.A.S. AL0004 Small light weight microphone tripod
G.R.A.S. AA0008 Preamplifier extension cable with 7 pin LEMO to 7 pin LEMO

Optional accessories

G.R.A.S. AM0029 Pole adapter
G.R.A.S. RA0010 Adapter for Pistonphone calibration
G.R.A.S. AL0001 Desiccator for Type 41AL
G.R.A.S. AM0009 Windscreen for 41AM/CN/AL/AO