Specifications

The peak power filter is used to reject detections that don’t reach a re-
quired peak sound pressure level during the duration of the call. Like
the trigger level , this setting is referenced to the current value of the
noise floor. It should be higher than the trigger level by at least 3 dB
(default is set 6dB greater).
The minimum duration filter is used to reject detections that don’t last
long enough. Many of the false detections due to insects can be consid-
ered “pop” noise. They are very short duration bursts that last only frac-
tions of a millisecond. In comparison, even short bat calls last longer
than a millisecond, and echolocation calls are normally even longer.
The minimum duration is defaulted to half a millisecond. This value has
proven to work well against most bug interference.
The fit restriction filter is used to reject detections that don’t meet the
selected curve fit restrictions. If the fit restriction is set to high, all de-
tections are required to closely match the internal curvature model. If
the fit restriction is set to standard (or medium), all detections are re-
quired to match the internal curve model, but with more tolerance for
error. Finally, if the fit restriction is set to low, the fit tolerance is set
low enough that most detections will pass except those that no creature
could possibly create.
The pop filter is used to reject pop noise like static discharging, which
is common in electrostatic or capacitive sensors, especially when oper-
ated in high humidity. It is also useful, for filtering out other false detec-
tions like rain drops hitting the detector.
Finally, the filter bank provides a selectable set of filters that are based
on the scanned parameter measurements. These are primarily intended
to allow SCAN’R to be operated to search for a particular call type, be-
cause they are very selective. Please see sections 3.8.1 and 3.8.2 for a
description of the parameters.