> How have others dealt with this frustration? How have you worked
around it? Anybody have an airplane noise canceling microphone?!
Should we be hoping the price of oil goes through the roof?
John,
When I was a Film Recordist, engine noise was the worst single
problem. The Production team seemed to send out deaf folk
to choose period locations. A favourite for Victorian dramas was Syon
House which is beautiful with sweeping parkland and in the
London area. Unfortunately it is also in line with one of the Heathrow
runways and they alternated these on a two hourly basis. You could
just cope with the other runway but not with an easterly wind and
planes taking off over you once a minute.
The problem is that engine noise is simply part of out environment and
we can only minimise it, not eliminate it. Minimising noise was part
of my job description, but it was never explained how this should be
done so it was up to us to work that one out.
Directional mics are important and also knowing where their side lobes
are. That's why I use MKH-416's and 816's. M-S rigs give an excellent
front stereo image, but are essentially omni so you need quiet
locations for them. Cardioid mics have a very active pickup
vertically, so don't help with overhead noise or ground reflections.
All types of mic will often benefit by being used low, especially if a
bank or rise blocks off a source off engine noise as from a road. Look
for any feature which could blank off a noise source and listen as you
move the mics around.
This won't help with overhead aircraft, but they will be too loud
anyway, but putting a hill between you and a distant flight lane can
help. While you are listening for noise sources, don't forget surfaces
which can produce echoes, like buldings.
However, the main method is simply to wait for quiet periods, or
record long and select later. It's a matter of living on your wits and
being inventive. By experienc you can judge what noises can be reduced
by filtering or masked by wind or other natural noises.
Filtering:
I use a bass roll-off on my SQN mixer as standard, but I have an
"antidote" equalisation if I want to put the full bass back in. This
avoids LF modulation and "blocking off" on the original recording.
With much birdsong, you don't really need the bass background noises
and I use a gently curved high pass filter at 6dB per octave. It
starts rolling off at 800 Hz, but is inaudible at 400 Hz, and
increasingly sloping below that.
As a warning about filter curves, any change in slope greater than 6dB
per octave will cause ringing at the turnover frequency which can
produce messy artefacts. A sharp kink produces ringing at about the
turnover frequency, but with a gentle curve, even a steep filter will
produce less audible artifacts. In any case, a steep bass cutoff
filter will make a recording sound very thin and nasty. Much better is
to use a smooth filter more than once.
I've got Audacity scripts for EQ curves on:
http://www.stowford.org/sounds/eqcurvesadd.txt
There is a graim mill about a mile away from here which produces a
single frequency whine around 770Hz which the wind sometimes blows in.
I've got a fine exactly tuned notch filter which reduces this by about
6dB without affecting the wildlife sounds.
I also sometimes use the Audacity noise reduction routine on HF noise
from the quietist parts of a recording. All noise reduction produces
artifacts, but if you keep to high frequencies only, these are
inaudible. Again I check that this is not affecting the wanted sounds,
but a 6dB reduction in HF white noise makes the recording more
pleasant. Any equalisation reducing the higher frequencies usually
sounds bad, especially with birds going up to the limit of hearing.
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
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