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)
- a special ½″ (12.7 mm)
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 (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. 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 ⅓ 13-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|
|Temperature range, operation||°C / °F||-20 to 60 / -4 to 140|
|CE/RoHS compliant/WEEE registered||Yes/Yes/Yes|
Typical frequency response
|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. RA0090||Pistonphone Coupler (for 94 dB re. 20 μPa)|
|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|