Using SM2BAT to monitor Bats
11
Song Meter SM2BAT
Copyright © 2009-2011
Post Processing
A .WAC file is created for each scheduled recording segment. In the
advanced program above, for example, a .WAC file would be created
every hour from sunset to sunrise.
The
Song Scope
software can open .WAC files natively. To quickly
locate and review potential bat echolocation calls in a long triggered
recording, you can set up
Song Scope
band-pass and detector
parameters and use the batch scan feature.
The
WAC2WAV
utility (available at no charge on our web site) can
convert the .WAC files into standard .WAV files for analysis by other
programs. Usually it is best when processing triggered ultrasonic
recordings to use the “Split Triggers” feature. This will take a mono or
stereo .WAC file containing possibly many individual triggered events
(e.g. bat passes), and break them out into many individual .WAV files
for analysis.
The max duration and min spacing parameters let you selectively
restrict the duration of each created .wav file and to optionally ignore
detections to satisfy the desired spacing in order to fit whatever
monitoring protocol you may be used to. For example, if you are used
to using Time Expansion detectors that only record for 5 seconds and
then pause for 50 seconds while the time expansion buffer is recorded,
you could select a max duration of 5 seconds and a min spacing of 50
seconds to simulate this behavior. By default, all detections are
included in their entirety.
The compensation filter may be selected to digitally alter the signal to
compensate for the SMX-US microphone by effectively altering the
frequency response to match approximately a 240X. This may be
helpful for analysis by automated classification software that relies on
the frequency response of the 240X to match known bat recordings.
The “Skip Noise” feature can be used to further analyze each candidate
trigger to determine if it contains actual bat echolocation calls (or other
biological activity) rather than just noise. The algorithm looks for the
presence of narrowband energy in the specified frequency band with at
least the minimum specified duration. Files that do not meet this
criterion are still split out as .WAV files, but the filename is prepended
with the prefix “NOISE_” so they can be set aside.
