BRUEL & KJAER 2204 - 5 Accuracy of Measurements; Condenser Microphone

5. Accuracy of Measurements
The Condenser Microphone.
The sensitivity of the 1" Condenser Mncrophone Type 4131 which is normally
supplied with the Sound Level Meter is approximately 5 mV/,ubar and it ha,
a linear frequency response from 20 Hz to 18 kHz to within ± 2 dB at 0°
incidence . From 20 Hz to 15 kHz the response is linear to within ± 1 dB.
Each microphone is supplied with a calibration chart giving a complete
~ , t::.,O~_'eo"""H I , O "III-2 00 11
M eot ui'M UU. • ovtputof o oaU!oct...toll-..tU.
b".'~':r.~:!!.!. ~~ ; n;~~· . ;o;,j ; • <Ill IS 4 K
~ .• 4. 68 ... .. •. .,y ,ll bOr .••• :-" 46 .6 db,. , '1 / JIIHlr
Co o1riQ t o,.... ol rc ui, H Pieltlwltl' l
• .... 5.37 ....... ,.V / I' IIor •.. .' ':"'4 5.4 .n.,. , V/ l'b &r
c;m.=:.::- - ~~~=·.~ , .=.,~~· · "
... .. +0.6 ....... _ .. 111 11 .
~~Ui k .... •II.I< I I OO V~I o riu\l on '
. 67.1 ....
, ......... - ..... 26 ... .... . .c
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"-' • UMH........._. ..... 56 .. ... . "ft
o. "' .. 7::3.- 62 a~
1
.,
0
tu ,. ..... R.S.
~ - ((((( 1 ~
$u,..,..erlaM Sp.c lflcri CMU
o..w.......,, •. oa e l noto l 2a.n- ).
o.:.'~ l:s. .r: ... ~ ;:os~ .
......,.,..._., , . ,....._,y _ e~ .
..... . ._. ..., ,. .._.UI UMI ... pt'N. 0. 2o .....
T L == ~~~II-IO aM + WC I
~ ::::::: =~"' ' ~"-- · I Afo,
~ ~:.:'.'::'=~ ~ U.... o. llllb , lft
100 1 000
Hz
10000
M%311
Fig. 5.1. Typical calibration chart as supplied with the microphone cartridges.
The automatic plotting process used in production has an accuracy of o.2 dB
up to 10kHz and o.5 dB up to 20kH z.
-1
0 100
20 15
200
10
300
400
5 4
500
3
600
2
700 SOOmmHg
O.S 0 Km Above Sea Level
,-----~----------~------~-----,------r----
90000 40000 20000
10000
5000
0 Feet (standard atmosphere)
I ll .II~
Fig. 5.2. Microphone sensitivity at 400 Hz as· a function of the static ambient ·
pressure. The corresponding altitudes are also given on the curve.
27