Typical applications and use
- Very Low Sound pressure measurements
- Lownoise product measurements
- Sound power measurements at low sound pressure levels
- Measurements on hard-disk drives, computerproducts, quiet rooms etc.
The Type 40HH comprises:
- a special high-sensitive ½″ (12.7 mm)
G.R.A.S. 40AH Condenser Microphone
- a special ½″ (12.7 mm)
G.R.A.S. 26HH Lownoise Preamplifier
The preamplifier and microphone are an individually-matched combination. To complete the system,a special single or 10-channel power module isrequired and is available, i.e. G.R.A.S. 12HF for single-channel measurements or G.R.A.S. 12HM for multi-channel (1 to 10) 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. 40AHMicrophone 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-fi eld. 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 ⅓ 13-octave bands for both the linear and A-weighted cases.
Frequency range (±1 dB) Hz TBD Frequency range (±2 dB) Hz TBD Frequency range (±3 dB) Hz TBD Dynamic range lower limit with G.R.A.S. preamplifier dB(A) TBD Resonance frequency kHz TBD IEC 61094 designation TBD Temperature range, operation °C / °F -30 to 70 / -22 to 158 Temperature range, storage °C / °F -40 to 85 / -40 to 185 Temperature coefficient @250 Hz dB/°C / dB/°F TBD / TBD Static pressure coefficient @250 Hz dB/kPa TBD Humidity range non condensing % RH TBD Humidity coefficient @250 Hz dB/% RH TBD Influence of magnetic field @80 A/m, 50 Hz dB re 20 µPa TBD Influence of axial vibration @1 m/s² dB re 20 µPa TBD CE/RoHS compliant/WEEE registered No/TBD Weight g / oz / TBD G.R.A.S. 12HF Power Module (1 ch.) G.R.A.S. 12HM Power Module (10 ch.) G.R.A.S. AM0069 Windscreens (set of 5) G.R.A.S. 42AA Pistonphone G.R.A.S. RA0090 Pistonphone Coupler (for 94 dB re. 20 μPa) G.R.A.S. AL0006 Tripod G.R.A.S. RA0093 Tripod Adapter G.R.A.S. AA0046 3 m Ext. cable G.R.A.S. AA0047 10 m Ext. cable G.R.A.S. AA0048 30 m Ext. cable
- a special ½″ (12.7 mm)