CESVA DC112 - Verification in Units of Equivalent Sound (Leq)

DC112d/DC112
User’s manual
39
8.1.2 Verification in units of equivalent sound (Leq)
A) ABSOLUTE ACOUSTICAL SENSITIVITY
a) Switch the DC112 to the menu “SENSITIVITY ADJUST”.
b) Apply a level of 94,0 dB to the microphone of the DC112 with the sound calibrator,
and wait 10 seconds.
c) Adjust the sensitivity of the meter so that the L
AT
indicated is equal to the level of the
last calibration of the calibrator minus the free-field pressure correction of the
microphone at 1 kHz (0,1 dB), rounded to the nearest tenth of a dB resolution.
d) Select L
A1”
and note the value measured.
e) Obtain the reading in reference conditions:
L
CR
= L
A1”
+ Cpcl
1kHz
– L
C
+ 94dB
where:
L
CR
- Reading in reference conditions
L
A1”
- Measured value of L
A1”
Cpcl
1kHz
- Free-field pressure correction at 1 kHz (0,1 dB)
L
C
- Level of calibrator in reference environmental conditions
B) FREQUENCY WEIGHTING
a) Insert the microphone into the multifunction acoustic calibrator.
b) Generate a sinusoidal signal of 1 kHz with a level of 94,0 dB.
c) Select L
A1”
and note the value measured.
d) Change the frequency to 63,1 Hz, 125,9 Hz, 251,2 Hz, 501,2 Hz, 1995 Hz, 3981 Hz
and 7943 Hz. Note the values measured.
e) Obtain the free-field response: add the free-field correction to this response.
Rcl
f
= L
A1”f
+ Ccl
f
– 84dB
Rcl
f
- Free -field response to frequency f
L
A1”f
- Measured value of L
A1”
at frequency f
Ccl
f
- Free-field correction at frequency f
C) LINEARITY
a) Substitute the microphone with the electrical signal adaptor and connect it to the
function generator output.
b) Select L
A1”.
c) Adjust the level of a reference sinusoidal signal of 1 kHz for an indication de 94,0 dB.
Increase the level of the signal in increments of 5 dB, up to 140,0 dB.
Return to the level of 94,0 dB and reduce the level of the signal in decrements of 5
dB, down to 50,0 dB.
Note the measured value and calculate the linearity error for each level.
EL = L
A1”
– L
EL - Linearity error
LA1” - Measured value of LA1”
L - Theoretical level
d) Repeat with a sinusoidal signal of 63 Hz. Upper limit: 114,0 dB.
e) Repeat with a sinusoidal signal of 8 kHz. Upper limit: 139,0 dB
.