Larson Davis SoundExpert LxT, Руководство пользователя

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7-6
Acoustic Calibration LxT Manual
temperature (23° C) and near sea level (101.3 kPa) then no
other corrections need to be made. For example, if the
calibration sheet for the CAL200 indicates 113.98 dB for its
level when set to 114 dB then set the Cal Level in the LxT to
113.86 dB and 1000 Hz.
When the microphone and instrument are at a temperature
other than near room temperature or static pressures not near
sea level, then corrections need to be added for the ambient
temperature and the prevailing static pressure. Check the
calibration data shipped from Larson Davis with the
CAL200 to get these corrections. The corrections can be
added to the level obtained in the previous paragraph to get
the actual level of the CAL200.
The 377B02 microphone's sensitivity varies with static
pressure. If the instrument is calibrated in one environment
and moved to another, then the sensitivity changes (after
stabilization) depending on the change of temperature and
pressure. The coefficient of static pressure is -0.01 dB/kPa.
If the system is calibrated at 85 kPa for instance then it is
0.16 dB less sensitive at sea level (101.3 kPa). The
sensitivity of the 377B02 and LxT vary slightly with
temperature also. The coefficient of temperature is +0.009
dB/°C. If the system is calibrated at 18° C then it is 0.045 dB
more sensitive at 23° C.
The Larson Davis 3" Wind Screen has less than 0.05dB
effect on the system response at 1 kHz.
Set the CAL200 level switch to 94 or 114 dB.
Calibrating the LxT2 and 375B02 microphone
The CAL200 and CAL150 provide a nominal pressure level
of 94 dB or 114 dB. The exact levels are printed on the
Larson Davis calibration sheet that came with the calibrator.
When using a free-field microphone, the pressure level at the
microphone diaphragm is slightly different. Thus, a free
field correction of -0.12 dB (0.03 dB uncertainty at 95%
confidence level) should be applied to either of these levels.
If the calibrator and instrument are near room temperature
(23° C) and near sea level (101.3 kPa) then no other
corrections need to be made. For example, if the calibration
sheet for the CAL200 or CAL150 indicates 113.98 dB for
it's level when set to 114 dB, then set the Cal Level in the
LxT to 113.86 dB and 1000 Hz.