BRUEL & KJAER 2209 - Relative Humidity; Electrostatic Fields; Magnetic Fields

In these records, curve I is the reading of the complete meter and micro-
phone. Curve
II is the noise at the microphone position measured by a
stationary sound level meter. Curve Ill is the complete meter, but with the
microphone replaced by a dummy with the same capacitance as the one
inch microphone, but with negligible acoustic or vibration sensitivity. As is
to be expected the microphone is most affected when the vibration is
perpendicular to the diaphragm. The noise from 1 g RMS can then amount
to an equivalent SPL of about 88 dB.
5.9. RELATIVE HUMIDITY
The microphone is unaffected by relative humidity as long as no
condensation occurs inside it. For the meter as a whole, the effect of
humidity is negligible (less than 0.5 dB) up to 90% RH.
5.10. ELECTROSTATIC FIELDS
The sensitivity of the microphone to an electrostatic field is negligible as
long as the protection grid is kept on. For the rest of the meter, electrostatic
fields have negligible influence.
5.11. MAGNETIC FIELDS
The effect of a magnetic field on the microphone and input stage is
negligible. A magnetic field of 1 0rsted (80 A/m) and 50 Hz produces an
equivalent S.P.L. of 36 dB (Lin) on the meter and input stage.
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