http://soundcloud.com/user2340027/tmn-bat-wings-ear-cave-april-2010
I'm sharing this not because I think it is good, but because I think it
was an interesting idea that fails for a number of reasons, which
probably are worth sharing.
The recording is of the flight of bats in the Ear Cave, Taman Negara,
Malaysia. Conditions inside the cave were hot and humid (unfortunately I
do not have numbers, but I had a fairly dry shirt when I went in, and a
completely sodden one when I came out less than an hour later).
Obviously the sound of bats wings is not loud (though when they flew
close they could produce "wind noise" from the microphone, even though I
was using a windshield!). The microphone (AT 8022) does not have a
published floor noise level in the AT data sheet, so I can only assume
it is something they are not particularly proud of. To get the
recording to normal listening levels I used the following method (with
Audacity):
- identify any obvious sound peaks, zoom in a lot and reduce the volume
of the peak (generally by -3 or -6 dB)
- normalize
- repeat until the floor noise started to become objectionable when
listened to with headphones
I am assuming that the white noise audible in the background is due to
microphone self-noise. In the cave there was no running water, and the
nearest running water outside is some distance away.
- is this noise typical of microphone self-noise?
Water dropping from the cave roof is audible throughout. However some
of the sounds both sound and look different from those that are clearly
water drops. For example in the section 3m 42.023 s to 3m 50.395 there
are three short duration louder sounds. The first is clearly a water
drop, the second two sound much harsher, and have a very sharp attack.
- could these sounds be humidity-induced microphone noise, or are they
just different sounding water-drops?
On the problem of recordist noise, for this kind of recording I would
consider in the future using a long cable run between the microphone and
recorder, though even in this small cave several tens of metres of cable
would be needed. (Otherwise learn how to keep completely still, and
learn sign-language :-)).
For improving the microphone, I am considering a pair of Rode NT1As, set
up in some sort of boundary array. Obviously a different recorder would
be needed (and/or a pre-amp providing the phantom power). One thing I
learned from this trip is that being able to carry all the kit in a
small bag is really useful, as is having a reasonably short set-up time.
The AT8022 in the Rycote windshield + tripod went into a sports bag OK,
and could go through the narrow access to the cave (would use a better
small rucksack in the future).
I would appreciate any suggestions for better microphone + recorder
combinations that would meet the portability requirement (ideally with
schematics if any DIY is involved :-)).
Thanks,
Richard
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