John,
The bottom line is what a recording sounds like to the recordist's ears and=
of course to other people listening to the recording.
My Sennheiser MKH416's have an HF noise level which is usually drowned by
natural hiss from wind on leaves and a distant stream, but the pile of
bedclothes test reveals an HF tip-up which is close to where the thermal
noise of air would be. One day I will prove this by putting it Into a
vacuum.
> Here is a wild guess, and I'm not an acoustics expert, but If there is a =
way to apply the sound level dampening over distance rule where we hear a s=
ound level drop of 6 dB per doubling of distance, maybe we could say that a=
6 dB decrease in self-noise would allow us to hear twice the distance for =
a given location. Of course that would be a gross generalization.
We've got such a rule, the sound level from a single source drops 6dB every=
time you double the distance, plus some other factors like HF sound
absorption. If you can get closer to a wildlife sound source, you can alway=
s
improve the signal to background-plus-mic noise ratio.
Whose definition of "self noise" would you use? To have any meaning, this
has to be an "equivalent self noise" in other words the acoustic noise leve=
l
in Phons which would give the same noise level as the mic itself, in other=
words a sound which would raise the total mic noise level by 3dB.
An "excess noise" figure means noise in excess of the fundamental noise of=
the air itself using a stated weighting. Or should do with a quality mic.
Anything goes to sell cheap mics. :-) "Self noise" is often what a
manufacture wants to define it. It's just noise.
Other specs relate the total mic noise to 0 Phons but perhaps not saying so=
,
or even give the noise of the mic preamp with the capsule disconnected. Thi=
s
is meaningless to anyone who wants to actually use the mic, but looks good=
on sales blurb.
A quality mic spec will sometimes look inferior to a hyped cheap mic becaus=
e
the base level has not been defined. The final verdict is of course - as I=
said - given by a pair of good ears.
David Brinicombe
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
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