BRUEL & KJAER 2203 - Tripod Mounting Threads

Determination of K -factor
The 2203 along with other B & K instruments is calibrated for a
standard microphone sensitivity of 50 mV / Pa which equals -26 dB rel-
ative to 1 V / Pa ( 1 Pa = 1 N/ m
2
= 1 0 J.Lbar) .
Since differing microphone sensitivities and the attenuation caused by
various adaptors, extension rods, and input stages of sound level meters
result in a sensitivity other than this standard sensitivity, a correction
factor K must be added to the meter reading to give the actual sound
pressure level. K is determined by the formula :
K = K
0
-
input gain - adaptor gain
Thus, using a one-inch Microphone, for example, the open circuit cor-
rection factor K
0
of + 0, 6 dB is found on the microphone calibration
chart . On the back of the chart is found the input gain of the 2203
(- 1 ,2 dB). If the 2203 is used with Extension Rod UA 0196 which has
a gain of -0,1 dB (attenuation of + 0,1 dB) we can calculate K:
K = 0,6 - (-1 ,2) - (-0, 1)
= + 1,9 dB
For
half-inch Microphones, the input gain given on the calibration
chart includes the attenuation of certain adaptors and extension rods
which are listed.
3.3. SOUND MEASUREMENTS
3.3 . 1. General Considerations
1. Select a Microphone with appropriate dynamic range, frequency
range and directional characteristics. Also select appropriate accesso-
ries (See Chapter 6) for various environmental and measurement con-
ditions .
2. Whenever possible mount the 2203 on a tripod and use the flexible
extension rod to minimize interference from reflections from the me-
ter itself and the body of the observer. Stand at least one meter be-
hind the instrument to reduce interference when making readings.
Position the Microphone so it faces the sound source .
3.
When measuring sound fields other than normal incidence , use the
Random Incidence Corrector UA 0055 on the one-inch free field Mi -
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