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Fig.A.2
Nomogram for
determining the error
in a pressure-residual
intensity index
measurement due to
vent sensitivity
+12
+15
+18
+24
A.2
Effect of Ambient Conditions
Temperature and Atmospheric Pressure Changes
To determine the sound intensity level correctly, the air (gas) density should be entered into the
measurement system. The density varies with ambient temperature and pressure. For some
sound intensity analyzing systems the value of density is fixed to 1.205 kg/m
changed, so the displayed level has to be corrected depending on the actual calibration or
measurement conditions. The correction is 0 dB at the reference conditions 1013 hPa and 20 °C.
(L
- L
)
p
l
dB
0
+3
+6
+9
+21
20
40
Sensitivity to Sound Pressure at the Equalization Vent
Measurement Systems r: 12mm
S
[20 Hz]
v
Measurement Systems r: 50mm
S
[20 Hz]
v
160
80
Freq.Hz
891394
3
and cannot be
33
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