Hi Rob,
Thanks for suggestion, but from the recordings, bat activity at least seems=
highly sensitive
to temperature (warmer night in a cold interval =3D> a lot more bat calls).=
This is also
reasonable since insect availability (assessed by light traps) ramps up whe=
n it is warmer.
The important issue Klas's observation raised is that low detection of bat =
acoustic activity
at low temperatures might result in part from lowered microphone sensitivit=
y and a
resulting decrease in detection volume. So how much is biological response =
and how
much is instrument effect?
There are a couple of detailed papers from a few decades ago that measured =
attenuation
with distance for acoustic signals over a wide frequency range at biologica=
lly relevant
temperatures and humidities (though not very cold if I recall correctly). T=
he results are
surprisingly complicated in the ultrasound.
Bill
> >Hi Klas,
> >The idea of response changes with low temperature seems entirely
> >reasonable. Can you
> >suggest from tests or speculate on what would happen to sensitivity
> >and frequency
> >response?
>
> Hi Bill--
> As you are running long takes, perhaps you could extract and compare
> some samples from bitter cold and warmer nights a few days apart with
> the mics in the exact same spot. While you're at it, it would be
> interesting to ponder potential air density differences! :-) Rob D.
>
>
> --
>
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