Re: Carbon microphone amplitude

Rune D. Jørgensen wrote;
"I'm building a microphone amplifier and filter for a communication
system for my motorcycle. I'm filtering away frequencies below 1KHz to
suppress wind noise.
I have a microphone that has a resistance of 1.8K ohm, so I guess it's a
carbon. I have read somewhere that I should have approximately 1mA
running through it. Is that correct and what kind of amplitude should I
expect out of the microphone?"
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Re;
Assuming it is a carbon microphone and you don't have the make and model
#. There is no current/sound pressure thumb-rule, that I know of, that
would cover all carbon mikes. Although the characteristic resistance for
yours may be 1.8kohm, the voltage amplitude produced for a given sound
pressure with 1 mA excitation is highly dependent on the surface area
and frequency response of the diaphragm, the particular density response
of the carbon pack, and the characteristic input impedance of the
electrical load on the microphone and it's power supply. Without these
particulars you are just guessing, as are we, and you will probably need
an oscilloscope to determine the electrical response to voice in your
planned circuit.

Dan Akers

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