Microphone Polarisation; Microphone Sensitivity - Castle group dBAir Operating Manual

Microphone Polarisation

Microphones require a polarisation voltage to operate and are manufactured in two
ways.
Externally Polarised
These microphones require an external charge for the microphone to operate which is
generally 200V and supplied by the sound level meter.
Pre-Polarised
These microphones generate the polarisation voltage internally and do not require the
externally generated 200V polarisation charge.
All microphones supplied with dBAir sound level meters are Pre-Polarised.

Microphone Sensitivity

The sensitivity of a microphone is determined by the output voltage it produces for a
defined sound source.
Microphones are manufactured with numerous sensitivity levels and operate within a
specified tolerance. Different microphones of the same model may therefore give slight
differences in readings when used on the same sound meter. To allow for this all dBAir
sound level meters have been designed to accommodate any variations in the tolerance
of the supplied microphone up to ±3dB.
All models of the dBAir sound level meter with Class 1 approval have been designed for
microphones with a sensitivity of 50mV/Pa.
All models of the dBAir sound level meter with Class 2 approval have been designed for
microphones with a sensitivity of 25mV/Pa.
Great care must be taken to ensure the microphone and sound meter sensitivities
match otherwise incorrect readings will occur.
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