I think there are misunderstandings here:
<< I=B9m wondering how you=B9d do this ? Why wouldn=B9t you roll off the
bass post-recording instead?
Because the recorded signal is distorted because of input stage
clipping, just as Scott says.
I really don=B9t see how you could simply put back bass that was
Well, it "was" recorded, but at a lower level, not causing clipping.
Then it can (somewhat) be recovered.
Scott, with modern recorders it has all got twisted and uncertain.
1/ Using a certain recorder model "A" - where, in the chain, is the
internal base filter? Will wind amplitude distort the input stage,
even if the base filter is used? We don't know that, and it seems to
vary with models.
2/ How does recording level interact with noise? We don't know that
either, and it varies with recorder models. The Olympus LS makes much
more noise at 16bit than on 24bit, for example, regardless of the
recording wheel setting. And noise figures vary a lot, depending on
sensitivity setting "low" or "high", regardless of the recording
level showing on the meter, but depending on the sample rate.
"So, a long answer to your query, but the short version is that we
have to start with the best possible recording of the original event,
& not plan on fixing problems later, since many of the problems
relating to wind actually can't be fixed adequately in post."
The two Telinga models PRO8 and PRO8W has a on/off switchable
12db/octave base filter with it's -3bd point at 270 hz. If this is
not enough to prevent clipping, it is usually too windy to record
anyway, because of wind in bushes and trees etc.
Still, I have recorded flying common terns and black terns
simultaneously in full storm (with base filter!!) holding the Telinga
with both hands, otherwise it would fly away over the Atlantic.
It doesn't sound good, but for the person who wants to know the call
difference between the two species, the recording is good enough.
At 17:12 2012-09-21, you wrote:
><< I=B9m wondering how you=B9d do this ? Why wouldn=B9t you roll off the
>bass post-recording instead? I really don=B9t see how you could simply
>put back bass that was never recorded.>>
>To further elaborate on David's & Klas' responses, wind rumble on a
>mic is a very high amplitude signal. If you adjust the record gain
>so that the wind rumble doesn't distort, your desired sounds are
>recorded at a needlessly very low level, at a point where preamp &
>converter noise start interfering with the sound. If you don't
>adjust level for the rumble you get preamp overload & converter
>clipping which add upper harmonics throughout the spectrum,
>resulting in a ruined recording. I.e. it's not just bass which can
>be simply high pass filtered out at this point. So we use bass cuts
>(high pass filters) in order to preserve headroom in the original
>recording chain, headroom which can't be reconstituted in post production.
>Additionally, a high pass filter does not eliminate bass
>frequencies. It attenuates them. So bass is still recorded through a
>high pass filter, but at a lower level, & this is what David refers
>to by putting back bass in post. It's there & can boosted by the
>same amount as the bass cut on the mic/preamp/mixer in order to
>restore natural lows, if needed. Generally, nature has rather little
>energy in the lowest octave of human hearing most of the time,
>except for thunder, waterfalls, waves & a few other geologic events.
>So rolling off lows primarily serves to attenuate human vehicular
>noise. Wind rumble goes all the way down to DC & the gentle
>6dB/octave curve David mentions, even if at 50Hz is enough to
>eliminate the most pernicious effects of rumble while still allowing
>a reasonable sense of low frequency reality to be recorded.
>So, a long answer to your query, but the short version is that we
>have to start with the best possible recording of the original
>event, & not plan on fixing problems later, since many of the
>problems relating to wind actually can't be fixed adequately in post.
>"While a picture is worth a thousand words, a
>sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
>Yahoo! Groups Links
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S-748 96 Tobo, Sweden.
Phone & fax int + 295 310 01