Chapter 2 — Prepolarized Free-field
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" Microphone Type 4188
Effect of Vibration
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2.14 Effect of Vibration
The effect of vibration is determined mainly by the mass of the diaphragm and is at
its maximum for vibrations applied normal to the diaphragm. A vibration signal of
1m/s
2
RMS normal to the diaphragm typically produces an equivalent Sound Pres-
sure Level of 63.5dB for a microphone fitted with Protection Grid DD0525.
2.15 Effect of Magnetic Field
The effect of a magnetic field is determined by the vector field strength and is
normally at its maximum when the field direction is normal to the diaphragm. A
magnetic field strength of 80A/m at 50Hz (the test level recommended by IEC and
ANSI) normal to the diaphragm produces a typical equivalent Sound Pressure Lev-
el of 7dB. Higher frequency components in the microphone output become domi-
nant at field strengths greater than 500 to 1000A/m.
2.16 Electromagnetic Compatibility
See Chapter 8.