mstrong82 wrote:
This is a fit for something I want to make.
I want to make a mic for tracking wildlife. I want to make it so you can hear the
faintest, furthest away sounds. Anotherwords, I want to crank the gain up to
infinity and beyond and I DON'T want to hear transistor hiss.
Ah, but therein lies the rub. From looking at noise specs
for various size mics, from the experiments of one of our
members, and according to:
it seems that self noise has a large component that is
molecular shot noise from thermally agitated air molecules
impinging on the diaphragm which can only be reduced by
increasing the diaphragm diameter. A fairly simple argument
shows that increasing the diameter has the effect of
averaging that noise down relative to the signal.
A definitive experiment would be to compare the self noise
of a small electret at various air pressures, including a
near vacuum, which wouldn't be all that difficult if anyone
had a bell jar and a hand vacuum pump.
Bob
--
"Things should be described as simply as possible, but no
simpler."
A. Einstein
