At 7:44 PM -0500 12/28/04, Lang Elliott wrote:
>the low end is often
>clogged with distant pulsating rumble caused by manmade machinery.
Semi-random "walking" oscillations seem to be inherent in the lowest
range ~16-48Hz -whether man-made or the result of low energies in a
natural acoustic setting. Sometimes, when the pulsation seems more
pronounced over speakers than it was to the naked ear, the
reproduction is getting "tuned"-- that is-- a specific frequency or
group of frequencies is dominating bass playback. One can notch
filter the over-expressed bands if the subwoofer range is smooth
enough to effectively reduce the pulsing without amplitude
compression. If the subwoofer range is not smooth, the signal itself
tends to disappear with notch filtering because the speaker is
reproducing the only frequencies it can.
>
>It occurs to me that it would be extremely useful to get a totally quiet
>ambient recording, perhaps in the far north in dead of winter, which is fr=
ee
>of animal sounds or other nature sounds, but that has a great spaciousness
>and a solid low end that is not contaminated by rumble. One could filter o=
ut
>the high end of the recording using a low pass set somewhere below 1 kHz.
>Then the resulting recording could be used to mix with soundscapes where t=
he
>low end had to be filtered because of rumble.
I have some middle of the night recordings from rural and urban
settings that I've used for this. Oddly enough, I can still recognize
the recordings I mix in even after they are heavily equalized and
only holding up a portion the bottom three octaves. Of course,
material from the same location/mic array mixes in much easier. Long
takes to capture passages with very minimal presence and 24 bits--
these help too.
A few other low hz smoothing tricks: lower the sample rate in the
header to one-half or even 1/8th and drop the whole harmonic
structure down (I use Soundhack). Natural location tones around 80hz
are inherently smoother and will play much more smoothly at 20Hz
than those originally picked up in that range. Mix in about 20-50%.
Another is to record when the air is really really cold and dense-- I
learned this from sight impaired friends who call hot summer air,
"flabby." Lastly, mild compression with in conjunction with EQ.
typically 5-20ms attack with about the same release time and 1.5:1 to
4:1 compression ratios. I also manually remove a lot of "out of
control" moments Rob D.
>
>While this is cheating, to a degree, it would add back that deep
>spaciousness that is lost when the low end is or reduced.
Cheating or just getting the cardboard flapping to make sounds more
like the ones I remember.
>
>Lang
--
Rob Danielson
Film Department
University of Wisconsin-Milwaukee
________________________________________________________________________
________________________________________________________________________
"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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