Hi Richard--
Is your goal to document the space with the bats as best as you can?
If so, I think it has more promise than you suggest. Do you know what
those regular-spaced, 10-12 second long 5800K Hz tones are?
I assume some bat passes are so much closer/louder that they need to
be tamed before you can raise the playback level to hear softer
sounds in the distance with the acoustics of the cave. It might be
possible to address these transient peaks, adjust overall tonal
balance and stereo imaging in one step and avoid multiple steps and
normalization. If you'd like to post a 2 minute clip of the original
as a flac file, we can give it a look/listen.
As for your gear/array approach to the setting, an X-Y mic is not a
bad choice for a smaller space like this one. Mix placement can be
critical-- best to get away from the walls/ceiling/floor so the
reflections are balanced and chances of phasing are lessened. Might
be interesting to set-up the gear and leave for several hours. A
quieter mic might prove beneficial to focus on HF communications
after things settled down. (There are many ba experts who can address
these goals much better than I). As-is, the commotion of the wing
fluttering should be robust enough to get around an annoying amount
of self-noise. Rob D.
=3D =3D =3D
>
><http://soundcloud.com/user2340027/tmn-bat-wings-ear-cave-april-2010>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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