--- In Dan Dugan <> wrote:
> We did the five Muir Woods soundscape monitoring locations twice, in
> the night (midnight--2:00 AM) and sunrise (half-hour before
> sunrise--two hours after) time slots. On each pass we each did three
> locations, doubling up on the Ben Johnson Trail location, then
> splitting up to do two more each.
>
> That spot is about five minutes uphill from the end of the main trail
> that goes along Redwood Creek. It takes half an hour to walk there
> from the entrance. We were about twenty feet apart on the trail, both
> facing downhill towards Bridge 4 and the creek (not visible through
> the trees). It was an inky dark night, overcast with no moon, and the
> park was very, very quiet. On the way in we heard nothing but the
> creek.
Muir Woods has pretty diverse bat fauna. Several have most of their call
energy near the nominal upper bound for audio microphones (say 16-25 kHz).
Small condensers could have decent sensitivity above 20 kHz, but that
typically isn't shown in the factory specs for anything other than (expensive)
measurement microphones.
Larger bat detector condenser microphones are often optimized for 40 KHz and
above with sensitivity falling fairly steeply in the upper audio. They also
typically have subjectively high noise floors and may be quite humidity
sensitive.
Depending a number of things (notably antialiasing filters),
combining the high sampling rate A to Ds of the 722 (or other lesser digital
recorders) with a relatively inexpensive low noise floor broad band
microphone, could offer more recordists affordable access to numerous animal
sounds that formerly required expensive, bulky special purpose gear. There
are a lot of nocturnal insect signals in this range as well.
Any impression of the noise/sensitivity of the AT3032 above 20 kHz?
Bill R.
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