wbie)
Not sure if this is relevant, but we have sporadically encountered low cost=
dataloggers with defective crystal oscillators that emitted substantially i=
n
the upper audible or near ultrasonic. Enough to cause bats to not roost nea=
r the
supposedly passive logger.
Bill R.
--- In "John Hartog" <>=
wrote:
>
> When I look at spectrograms of recordings I made using NT1-A's with a
> PMD-670, I notice a narrow band about 200Hz wide between 16K and 21K.
> I'm pretty sure it's from the recorder not the mics because it is
> always stronger in the left channel. The band drifts over time, for
> instance it might start out at 16K and over an hour or so it gradually
> rises to 19K. My ears cannot hear it but frequency analysis shows a
> 5dB spike. The problem seems to disappear using the NT1-A's with a
> Rolls PB224 and my new MZ-RH10, though I haven't had much time to test
> that thoroughly.
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