I have made numerous recordings at altitudes up to 5400m with no
problems at all. I have done this in snow and ice, and at temperatures
below freezing (although I am not sure how much of that is due to wind
chill). I'm using a Nagra V and a Schoeps MS microphone rig in a
Rycote, with Mogami 2930 two-channel mic cable and Beyer DT250
headphones (the 250 ohm version for greater SPL). I've even made
recordings with the Nagra V 'floating' on the surfaces of frozen
lakes, but I have the optional aluminium handle on mine, which I fold
down so the machine is in its 'sit up and beg' position and has very
little contact with the surface it is sitting on.
There is a large black bird that exists at those altitudes in Tibet,
possibly some sort of crow or raven, and it has the most interesting
call - almost like an electronic beep or 'bloop'. The first time I
heard it was while recording the sound of Tibetan prayer flags blowing
in the wind on a high altitude mountain pass in November (Tibetan
winter), and it freaked me out, as if I was being pinged by a flying
submarine! I was wearing my headphones and, because the bird was
hovering above me, I found it very difficult to locate where the sound
was coming from; my headphones were telling me there was something to
my right side, reasonably close, but there was nothing to be seen at
ground level.
To keep warm, I usually crouch down low while the recording is taking
place, and I try not to move at all because the slightest physical
movement makes a lot of noise, primarily shoes crunching gravel as I
shift my centre of gravity to maintain balance, and the rustling of my
down jacket. So, I was trying to see what was making this sound purely
by moving my eyes around, rather than turning my head. I could hear
it, I knew it was getting closer, but I couldn't see anything at all.
I remember feeling scared, as if I was being stalked by something
quite alien, until the bird drifted into my peripheral vision and I
was finally able to associate the sound I was hearing with it.
BTW, it is hard to predict when those birds are around, but they tend
to spend a lot of time 'flying on the spot' in pairs, facing into the
wind but not really getting anywhere. The beep sound is their call to
each other.
Some interesting thoughts about recording at altitude:
As you know, it is very cold at those altitudes. I dress in layers;
for the types of recordings described above I normally wear Merino
wool thermals (top and bottom) followed by a Merino inner layer top, a
pair of lightweight trekking trousers (lighter and warmer than denim),
then a fleece jacket and a down jacket over the top of that. Also, a
thermal cap/beanie (that hopefully covers my ears but can be moved to
make room for headphones), gloves, and two layers of socks inside my
boots (one thick warm pair, one thermal liner).
This can keep me toasty warm for quite a while, but there are some problems.
Firstly, it is impossible to operate the equipment while wearing
appropriately warm gloves, so I take them off to make adjustments and
then put them back on again - in the places I am describing, if the
wind is blowing I can get by with my gloves off for about 10 seconds
before I have to plunge my hands into my pockets! Secondly, down
jackets are noisy; the slightest movement can make a lot of noise that
the microphone will capture, making hand-held operation a waste of
time. Thirdly, if you are at high altitudes it is often windy and the
air is thin and dry (very low humidity); combine this with all the
different layers of clothing necessary to keep warm and your general
moving around, and you become a huge static electricity generator! I
have often seen sparks leap about 5mm from my fingertips to the
chassis or knobs of my Nagra - fortunately, the Nagra has handled it
without any problems at all, although on some audio gear such sparks
will corrupt the RAM and cause strange software behaviour, making a
re-boot necessary. It might even do some damage, so make sure your
gear can handle this kind of thing, or else find a method to discharge
yourself before touching it.
Finally, one of the great things about the low humidity is that there
is less moisture in the air to absorb the high frequencies over
distance, and so you'll find that sound travels amazingly well. Sounds
from a considerable distance away are often captured with surprisingly
good HF detail and articulation.
I hope this is helpful...
- Greg Simmons
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