BRUEL & KJAER 4220 - Operation of the Pistonphone; General Operation Steps

Operation
General.
After the sound measuring equipment under test has been warmed up and
made ready for use in the 12()-130 dB range and with "linear" frequency
response, operation of the Pistonphone is as follows:-
(1) Fit the microphone of the equipment under test to the coupler
opening. The Piston phone can be held in one hand, in any position.*)
(2) Start the Pistonphone by pushing the gliding switch, and check the
batteries by pushing the switch forwards and backwards between the
"l\fcasure" and "Check" positions. A definite variation in frequency
indicates that the batteries are in good condition.
( 3) The Pistonphone's switch being in "Measure" position, adjust, with the
free hand, the sensitivity of the sound measuring equipment until the
db
+2
-2
-4
-6
-8
-10
-12
-14
-16
-18
-20
-22
8
I I I I I I
.....
Change
1
in
1
Sound Pr~s
1
s~r~
1
L~v
1
el-
-r-
r- ......
versus change in ambient pressure
......
for Pistonphone Type 4220 -;-----
......
:-....
:-....
............
......
......
r-...
i '-
-1 0
-r-
0,5
--
-~--
-1
,..._.._
1 \.
,.,._.. 760 750 740 730 720 710 700 690 680 670 mm~g
-- 0 100 200 300 400 500 600 700 800 900 tt- m Abo e Se L l
\
__ o tilt 1~0~
111
2
1
oo
1
o 1tt ~oo
1
o re~t v I eve
\
I I I
00
700
I
0,5 1
0.6
600
I
2
1,2
I I I II
3
1,9
5~0
I J
400
300
200
100 0 m
mHg
I
I
4 5 6 7 8 9 10 11 12 15 20 km Above
2,5 3,1 3,7 4,3 5,0 5,6 6,2 7,5 9,3 12.4 Miles Sea Level
160¥28
Fig. 11. Correction curve for operation at low pressures or high altitudes.
*)A slight variation in the noise produced by the motor can be noticed when holding the
pistonphone in diHerent positions. This has no relation to the frequency and the S.P.L.
produced.
14