At 9:15 AM +0000 3/26/09, Greg Simmons wrote:
>--- In
><naturerecordists%40yahoogroups.com>=
m,
>Lou Judson <> wrote:
>>
>> So I always use a spectrum analyser to
>> see things I may not hear <snip>
>
>I'm with you on this, Lou.
>
>I moved out of the controlled sonic environment of the professional
>recording studio some years ago, and have since found that a good
>spectrum analyser is essential. Most audio software has some kind of
>analyser to show what I can't hear on smaller speakers.
>
>One thing I am fond of doing it is using a low pass filter to remove
>everything *but* that questionable low frequency energy, and then
>crank it up in my headphones and/or speakers to see if I can
>identify what it is. Very rarely can I relate it to the valuable
>information in the recording itself. So then I remove it using a
>good linear-phase high pass filter. And even if I can't really hear
>that low frequency stuff, removing it often seems to clean up the
>recording.
>
>Certainly, for my purposes there is usually nothing of value below
>40Hz. Apart from being mostly man-related rumble, most listeners
>can't reproduce it properly anyway and, even if they can, won't
>notice it missing. So I usually get rid of that stuff without a
>second thought... But I'll always use a linear-phase filter with a
>very steep slope, so there is no obvious LF roll-off.
>
Greg, Lou, Robin, Marc--
Interesting string. I think we are talking more about "mixing," than
"editing." I usually have a sonogram window open when I mix too. The
bandwidth of most field recordings is very wide and the dynamic
ranges are usually quite low. My sonogram plugs are pretty crude.
Sometimes I can "see" a subtlety I'm trying to address but usually I
would have to stop and tweak the settings.
A discussion about how to address the lowest octaves in field
recordings should probably be prefaced with mic and array
information. Some mics/arrays emphasize the lowest three octaves
while others radically attenuate them. These recordings would require
completely different mixing approaches. Also a factor is desired
outcome. Is one trying to represent acoustic space, or focusing on
the calls of an individual species? etc.
When using mics in an stereo array that captures the breadth of the
energies down to 15-30 Hz, I usually find that the representation of
acoustic space suffers dramatically when I use high pass or
"roll-off" filtering of any kind. As with any part of the frequency
spectrum, the excessive resonance is the result of individually
emphasized bandwidths that are better addressed one at a time to
preserve tonal balance, and upper harmonics. The liveliness of the
harmonics formed in the lower mid-range will be severely impacted
when a fundamental is axed. I think of the lower mid-range as where
the most accessible cues for spatiality are established. I wish it
was possible to "remove" a sound once its entered a space, but we
have to work with what is there.
When one uses high-pass filtering, one is also removing the
fundamentals of the "good," un-exaggerated bandwidths too. I find
its harder to establish the "body" of the recording--its substructure
when all of the lowest fundamentals have been "zapped." All of the
frequencies in a field recording have been "tuned" by physical
dimensions of the "enclosed" space. Less desirable sounds often fill
the space from afar and mask other, more desirable sound sources, but
they do so in specific bandwidths, not evenly across the lowest
octaves.
Instrument makers have argued for centuries about ideal volumes to
enhance resonance. Field recordists walk into a forest, bog or canyon
and work with the volume that is there. The microphones we use
deliver extremely intriguing approximations but they fall
considerably short of replicating human auditory experience. There
is ground to make-up for in mixing.
Equalization of this nature really challenges one's monitoring
facilities. "Flat" monitoring of the lowest octaves with both
headphones and speakers is pretty much mandatory and room peaks and
dips in the lowest octaves (where they most often occur) make the
practice futile. Rob D.
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