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BRUEL & KJAER 4220 - Calibration with B&K Equipment

BRUEL & KJAER 4220
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Calibration
of
Sound
Measuring
Equipment
Consisting
of
a
"8
&
K"
Condenser
Microphone Connected
to
one
of
the
Following
Instruments:
(a) l\licrophone Amplifier
Type
2603
or
2604 (Fig. 15a).
(b)
Frequency
Analyzer
Type
2107
(Fig.
15b).
(c) Audio
Frequency
Spectrometer
Type
2111
or
2112 (Fig. 15c).
1.
Case
of
the "one
inch"
microphones
(Cartridges
Type
4131 or 4132).
For
calibration
by
means
of
the
Pistonphone,
the
control
knobs
of
these
instruments
should
be
adjusted
as follows:
(1)
POWER
to
"On".
(2)
INPUT
SWITCH
to
"Condenser
Microphone".
(3)
METER
RANGE
to
"120
dB".
(4)
WEIGHTING
NETWORK
to
"Linear"
or
"Curve
C".
(5)
METER
SWITCH
to
"RMS-
Fast".
(6)
RANGE
MULTIPLIER
to
"x
o.3
-10
dB".
The
measured
S.P.L.
in
these
conditions
is
read
directly
in
dB re. 2 X 10-4
,ubar,
as
the
sum
of
the
"dB
SL"
setting
of
METER
RANGE
switch
+
the
dB
setting
of
RANGE
MULTIPLIER
+
the
meter
pointer
deflection
in
dB. Cali-
bration
(item
(3)
of
the
general
procedure
p.
14)
consists
of
adjusting
the
indication
of
the
instruments
to
the
S.P.L.
value
produced
by
the
Piston-
phone,
by
means
of
the
screwdriver
operated
potentiometer
marked
SENSI-
TIVITY CONDENSER MICROPHONE.
With,
for
example,
a
Pistonphone
producing
124.1
dB,
the
deflection
should
be
14.1 dB.
4220
4132
2613
a.
::
-.
::
. .
~
·
-..!._~
-
~.!.
.....
.
..
·"
i
·=
~
2604
b.
c.
4220
4220
2107
2112
Fig.
1.5.
The Pistonphone used for direct S.P.L. calibration
of:-
(a)
Microphone
Amplifier
2604.
(b)
Analyzer 2107.
(c)
Spectrometer 2112.
(6058+
2. Case
of
the "1/2-inch"
and
"114-inch"
microphones
(Cartridges
Types
4133,
4134, 4135, 4136).
Due
to
the
lower sensitivity
of
these
microphones,
a
correction
has
to
be
made
to
the
"dB
SL"
global
reading
obtained
from
the
indications
of
the
19

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