Posted by: "Rob Danielson"
> I've been monitoring my results in northern woodlands in this regard
> pretty carefully and I agree. If I set the background ambience at
> -15dB, its very rare for an natural event to over-modulate. I set
> both the side and the mid at this level.*
I'm surprised you can get away with setting the background ambiance that
high. I've measured the difference between callers and background at as
much as 60dB with a sound meter, occasionally more. I set 15dB of
headroom basically on the callers most of the time. Though if I don't
expect any of the real problem callers to start up I may go higher and
more closely set on the ambiance. It's a judgment call, but I always do
set some headroom. I guess you could say I set the headroom based on my
imagination of what might call and not just what is calling at the
moment I set it.
Of course really quiet ambiance sites it can sometimes be a problem even
getting to a setting of -15dB. That 3 AM in the Florida swamp I was flat
out getting to -40dB, even the callers did not make -15dB, they were not
close. As I've noted that was one of the quietest sites I've had recently.
> my "safe" level could be higher than some recordists want to risk.
I think this is the bottom line. You learn your equipment and your
recording subjects. Then you decide on just what level of risk you are
willing to take. There is probably no level thats absolutely safe 100
percent of the time. Risk depends on the purpose of your recording and
what amount of processing you are willing to do too. If you can just
cut out a occasional over, then it get's easier. Each recordist has to
make their own decision on this, there is no absolute right way.
> *At night, unless I'm close to a pond or other active spot, I'm at
> full pre gain anyway and the natural ambience is well under -15dB
> unless its windy, raining etc
However, that owl, coyote or whatever can suddenly start calling right
next to you, and you might want to record them well. The risk of such
things being damaging rises with each bit of pre gain we crank in.
However, my experience is like yours, in such quiet situations we are
more likely to be hunting more gain than looking for clipping. And
cursing the distant trucks, airplanes, barking dogs...
> ** Assuming a modest dynamic range of 15-25dB, shouldn't we be able
> to get adequate saturation and headroom with digital media?
We can, though it's easy to get too focused on it and think we can't.
The tricky part is what's adequate. Digital does far better than analog
tape, and there were excellent nature recordings done on analog tape.
> Isn't bit distribution/resolution linear up and down the scale? Rob D.
That is actually the problem, sound is exponential. Though in practice
we can go fairly far down the bits with little effect.
I'm not as worried about loss of definition by using 15dB of headroom as
you tend to be. But I do try to avoid any more loss than necessary for
safety. The easiest to process recordings are always those that make
good use of the full range of the recorder, particularly the top part.
It was essential with analog tape, but it did not go away with digital.
Walt
|