TB 9-4931-413-50
(2) Turn function switch of sound-level calibrator (table 2) to 2000, 1000, 500, 250,
and 125 Hz, respectively. Record test instrument meter indication for each position of
function switch of sound level calibrator. Collectively, meter indication will not deviate
more than 3.5 db.
b. Adjustments. No adjustments can be made.
9. Weighting Network Response
a. Performance Check
NOTE
The following values shown in parenthesis apply to units with
11/8-inch microphones. Values not enclosed in parenthesis
apply to units with 15/16 inch microphones.
(1) Turn function switch of sound-level calibrator (table 2) to 125 Hz.
Test
instrument meter will indicate between 112.5 and 115.1, (112.3 and 115.3) db.
(2) Turn test instrument WEIGHTING switch to A.
Meter indication will be
between 96.5 and 99.1 (96.3 and 99.3) db.
(3) Turn WEIGHTING switch to B. Meter indication will be between 108.4 and
111.0 (108.2 and 111.2) db.
(4) Repeat technique of (1) through (3) above for frequencies and WEIGHTING
switch positions listed in table 3. Meter will indicate within limits specified. If not, record
actual deviation, and prepare chart of correction factors applicable to test instrument.
Table 3. Weighting Network Response Check
Sound-Level
Test Instrument
Calibrator Output
Weighting
Meter Indications (db)1
Frequency (Hz)
Switch Position
Min
Max
250
C
112.6(112.5)
115.2(115.5)
500
C
112.7(112.5)
115.3(115.5)
1000
C
112.6(112.3)
115.2(115.3)
2000
C
111.7(111.6)
115.3(115.6)
250
B
111.1(111.0)
113.7(114.0)
500
B
112.4(112.2)
115.0(115.2)
1000
B
112.6(112.3)
115.2(115.3)
2000
B
111.7(111.6)
115.3(115.6)
250
A
104.0(103.9)
106.6(106.9)
500
A
109.4(109.2)
112.0(112.2)
1000
A
112.6(112.3)
115.2(115.3)
2000
A
113.1(113.0)
116.7(117.0)
1Values
in parentheses are for test instruments using microphones 1 1/8 inches in diameter. Values not enclosed in parenthesis
are for test instruments using microphones 15/16 inch in diameter.
b. Adjustments. No adjustments can be made.
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